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Publication numberUS3569802 A
Publication typeGrant
Publication dateMar 9, 1971
Filing dateSep 16, 1968
Priority dateSep 20, 1967
Also published asDE1614605A1, DE1614605B2
Publication numberUS 3569802 A, US 3569802A, US-A-3569802, US3569802 A, US3569802A
InventorsBrauer Horst, Kuschke Renate
Original AssigneeSiemens Ag
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Dielectric capacitors with inner barrier layers and low temperature dependence
US 3569802 A
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Description  (OCR text may contain errors)

ited States Patent [72] Inventors Horst Brauer Munich; Renate Kuschke, Kreis Freising, Germany [21] Appl. No. 762,220

[22] Filed Sept. 16, 1968 [45] Patented Mar. 9, 1971 [73] Assignee Siemens Aktiengesellschaft Berlin, Germany [32] Priority Sept. 20, 1967 [33 Germany [5 4] DIELECTRIC CAPACITORS WITH INNER BARRIER LAYERS AND LOW TEMPERATURE 3,386,856 6/1968 Hoorlander 317/238 3,419,759 12/1968 Hayakawa.... 317/230 3,419,760 12/1968 Raleigh 317/230 3,426,249 2/1969 Smyth 317/230 3,426,251 2/1969 Prokopawicz 317/230 Primary ExaminerJames D. Kallam Att0rny-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: Dielectric capacitor structures (and method of making the same) comprising a plurality of bound together crystallites having a barium-titanate perovskite lattice structure of the general formula:

(B81 -My)OZ(TI1 yML )Og which includes at least two different doping substances, one of which predominantly effects N-conductivity in the interior of the crystallites and the other which predominantly effects P- conductivity on the surface of the crystallites. M" is selected from the group consisting of Ca, Sr, Pb, Mg and mixtures thereof; M is selected from the group consisting of Zr, Sn and mixtures thereof; at and y are numerals ranging up to one; z is a number ranging from 1.005 to 1.05 the first doping substance is selected from the group consisting of Bi, Ce, La, Nb, Nd, Pr, Sb, Sm and Ta; and the second doping substance is selected from the group consisting ofCu, Fe and Mn.

PATENTEDMAR'QIQYI SHEET 1 [1F 3 Fig.1

INVENTORS 5A7) u: a

Rs/v 7e k uscA/ka" ATTORNEYS PATENTED'HAR SIB?! 1 3,569,802

sum 2 nr 3 60 1.0 2 m 6 0 8 0 100 12.0 1141 1&0 180 INVENTORS si l Q WTTORNEYS DIELECTRIC CAPACITORS WITH INNER BARRIER LAYERS AND LOW TEMPERATURE DEPENDENCE The invention relates to dielectric capacitor bodies having inner barrier layers, more particularly-the invention relates to dielectric capacitor materials and bodies composed thereof having inner barrier layers and a low temperature dependence.

Electric capacitors, which heretofore have been referred to as barrier-layer capacitors" have a chemically reduced ceramic body generally composed of barium-titanate materials having dielectric layers therein formed through a reoxidation at the capacitor body surface. A disadvantage of these conventional barrier-layer capacitors" is that one can easily detect the thickness of the dielectrically effective layer at the surface of such bodies. This materially limits the application of such barrier-layer capacitors. Another disadvantage of the heretofore available barrier-layer capacitors (formed through reduction and surface reoxidation of a ceramic body manufactured in a conventional manner), is that they exhibit extremely small dielectric strength. Further, where an operating voltage of more than v. is contemplated, such known barrier-layer capacitorscannot, generally, be utilized.

Attempts have been made to localize the barrier layers formed through reoxidation at the surface of the crystallites. However, even in such so-formed crystallites, an operating voltage of only few volts is possible. Dielectric capacitors of the type described hereinbefore are disclosed, for example, in French Pat. Nos. 1,472,425 and 1,471,752 (owned by the instant assignee) and attention is directed thereto for additional details thereof. Generally, these disclosures suggest that barium-titanate materials are doped with, for example, Sb and combined with certain portions of copper or iron.

Dielectric capacitor structures having inner barrier layers must have the interior of the crystallites as conductive as possible. In instances where known doping materials are utilized, certain maximum quantities, in accordance with recognized teachings in the art, i.e. 0 Saburi, Journal of the Physical Soc. of Japan," vol. 14, No. 9, Sept. 1959, pp. 1159- l 174, particularly page 1173, and W. l'leywang, Journal of the American Ceramic Soc., vol. 47, No. 10, Oct. 1964, pp. 484-490 of such doping substances are necessary to achieve a maximum conductivity in barium-titanate materials. From these teachings it becomes apparent that for any of the known doping substances effecting N-conductivity, a particular optimum quantity or amount thereof must be utilized to attain the highest conductivity in barium-titanate crystallites containing the same. This highest conductivity is generally referred to as the maximum doping quantity for that particular substance. For example, for antimony (Sb) this quantity is about 0.1 percent by weight calculated as Sb O and for lanthanum (La) the quantity if about 0.3 percent by weight calculated as 1.21 0 Corresponding values can also be readily determined by workers skilled in the art for other doping substances, such as niobium (Nb), bismuth (Bi), neodymium (Nd), cerium (Ce), samarium (Sm), tantalum (Ta) and other rare earths or similar materials.

Heretofore known ceramic dielectric capacitor bodies contained copper (Cu) in quantities ranging from 0.01 percent to 0.05 percent by weight calculated as Cut) in relation to the total weight of the body or iron (Fe) in quantities ranging from 0.01 percent to 0.03 percent by weight, calculated as Fe O in relation to the total weight of the body. However, even these types of capacitor bodies, at room temperatures, exhibited relatively low DK-values ranging from 20.10 to 5010 Nevertheless, it appeared that the DK-values were extremely dependent on the voltage, since the individual crystallites had a conductive core and the application of voltage to the capacitor body at the outer electrodes appeared to only substantially decrease the crystal boundaries and allow a considerable field intensity to occur at such boundaries. Further, there is a substantially appreciable voltage dependency far below the Curie temperature or point (for example, at a Curie temperature of 1 C.

An important feature of the invention is to provide a dielectric capacitor body consisting of a plurality of crystallites (polycrystalline bound together in a disc-shaped, tube-shaped or foiled-shaped ceramic body composed of barium-titanate material having a pervoskite structure of the general formula:

wherein M" II is selected from the group consisting essentially of Ca, Sr, Pb, Mg and mixtures thereof; M is selected from the group consisting essentially of Zr, Sn, and mixtures thereof; x and y are numerals ranging from 0 to l, i.e. ranging up to one, and z is a numeral ranging from 1.005 to 1.05. This barium-titanate material is provided with at least two different doping substances, one of which predominantly effects N-conductivity on the interior of the crystallites and is selected from the grouping consisting of antimony (Sb), lanthanum (La), niobium (Nb), bismuth (Bi), cerium (Ce), neodymium (Nd), praseodymium (Pr), samarium (Sm) and tantalum (Ta) and the other of which predominantly effects P-conductivity at the surface layer of the crystallites and is selected from the group consisting of copper (Cu), iron (Fe), and manganese (Mn).

Another feature of the invention is to provide a polycrystalline (i.e., a plurality of bonded together crystallites) dielectric capacitor body wherein a plurality of insulating barrier layers are substantially uniformly distributed on the inside of the body and such layers are connected in series. Consequently, these insulating barrier layers provide a plurality of PN- transistions (i.e., PN-junctures) poled in blocking or passing directions.

Accordingly, it is an important object of the invention to increase the insulating stability and to lower the voltage dependence of the DKvalue of a dielectric capacitor body in accordance with its application.

Another object of the invention is to provide a dielectric capacitor body and a method of making the same having inner barrier layers and a low temperature dependence.

It is another object of the invention to provide a dielectric capacitor body having barrier layers located at the surface of the crystallites comprising such body. 1

It is yet a further object of the invention to provide a dielectric capacitor body having inner barrier layers that have substantially no visible thickness.

Other objects, advantages and features of e the invention will become more apparent with the teachings of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings in which:

FIG. 1 is a prospective elevational view, with parts broken away, illustrating a disc-shaped capacitor body constructed in accordance with the principles of the invention;

FIG. 2 is an elevated sectional view, with parts broken away, of a tubular-shaped capacitor constructed in accordance with the principles of the invention;

FIG. 3 is an elevational sectional view, with parts broken away, of a stack capacitor body constructed in accordance with the principles of the invention;

FIG. 4 is a sectional fragmentary enlargement taken substantially at the encircled portion designated IV in FIGS. l-3;

FIG. 5 is a graphical illustration of the DK-value of capacitors of the invention as a function of temperature for different sintering conditions;

FIG. 6 is a graphical illustration of the loss factor of the capacitors of the invention as a function of temperature for different sintering conditions; and

FIGS. 7 and 8 are graphical illustrations of the DK-value and the tangent of the loss angle Bas a function of temperature for capacitors of the present invention as a function of sintering temperature.

Before proceeding with a detailed description of the drawings, the composition of the barium-titanate crystallite having the perovskite lattice will be further described. As indicated hereinbefore, the dielectric capacitor bodies of the invention are composed of a plurality of bonded crystallites in a ceramic form. The crystallites are composed of bariumtitanate materials having a perovskite structure or lattice with a general formula of:

wherein M" is a material selected from the group consisting of Ca, Sr, Pb, Mg, and mixtures thereof; M is a material selected from the group consisting of Zr, Sn, and mixtures thereof; x and y are numerals ranging up to one; and z is a numeral in the range of 1.005 to 1.05. In other words, the quantity of the quadrivalent perovskite forming ingredient is 0.5 to 5 mol. percent greater than the quantity of the bivalent perovskite forming ingredient. These barium-titanate crystallites contain at least two different doping substances, a first of which is selected from the group consisting essentially of Bi, Ce, La, Nb, Nd, Pr, Sb, Sm and Ta which tend to predominantly effect N-conductivity on the inside or interior of suchcrystallites; and the second of which is selected from the group consisting of Cu, Fe and Mn which tend to predominantly effect P-conductivity on the surface layer or outer peripheral portions of such crystallites.

In accordance with the principles of the invention, the above defined dielectric capacitors of the invention have an increased insulating stability and a relatively low (and variable) dependence on voltage for the DK-value thereof in accordance with their application. This is achieved by including the aforesaid first doping substance (which predominantly effects the N-conductivity) in amounts ranging from 1.5 to 2.5 greater than the maximum doping quantity necessary to achieve the maximum conductivity of crystallites containing such doping substances; and by including amounts of the aforesaid second doping substance (which predominantly effects the P-conductivity) in the range of 0.01 to 0.15 percent by weight thereof. The amount of the doping substances are calculated on the basis of their respective oxides.

The DK-values discussed hereinbefore and hereinafter in regard to both the known and the now disclosed capacitor bodies, are the values for the dielectric constant (DK) and are conventionally designated far above the e-value (dielectric and are to the specified material. These DK-values are obtained by computing a dielectric constant (DK) through measurements of the capacity of such capacitors modified by the physical dimensions of the capacitor body. Thus, throughout the instant discussion reference to the DK will be understood to mean apparent DK as determined in the aforesaid manner.

Control of crystalline growth (a process known to workers skilled in the art) or the addition of tin (with a correspondingly simultaneous shift of Curie Point) are utilized to insure that the crystallites of the instant invention are of a medium size in the range of 20 to 300 my. and preferably in the range of 100 to 300 mp. (millimicrons). Such medium sized crystals exhibit an exceptionally large DK-value, however, the voltage dependence of the DK thereof tends to increase. Nevertheless, dielectric capacitors formed in accordance with the principles of the instant invention from the aforesaid medium sized crystals have exceptional utility, (or applicability) for example, as dielectric amplifiers.

In accordance with the preferred crystallite structures for the material comprising the dielectric capacitor bodies of the invention, antimony (Sb) is utilized as the first doping substance (previously identified) effecting the N-conductivity in amounts ranging from 0.15 to 0.25 percent by weight calculated on the basis of Sb O Copper (Cu) is utilized as the preferred second doping substance (previously identified) effecting the P-conductivity in amounts ranging from 0.01 to 0.15 percent by weight calculated on the basis of CuO.

The advantages of the instant invention become more obvious by the recognition of the fact that as the insulation of the surface or peripheral layers of the crystallites increase, more copper is forced into such peripheral layers of the crystal lattice. However, an apparent contradiction or difficulty prevented workers in the art from recognizing this fact, since an increase in the amount of copper above its known maximum doping proportion results in a noticeable drop of the DK-value and sometimes as low as the effective e-values. This contradiction may now apparently be explained or attributed to the fact that an increase in the amount of copper, reduces the conductivity of the entire crystallite, i.e. clearly indicating that the copper must enter into the interior of such crystallites.

Quite unexpectedly, surprisingly and in contradistinction to the teachings and suggestions of workers skilled in the art (as illustrated by the aforesaid literature) in regard to the optimum quantities of doping substances thought necessary, it has now been discovered that by increasing the amount of one doping substance, an increase in the amount of the other doping substance, i.e. copper, is possible. Such an increase results not only in the attainment of a considerable increase in the apparent DK, and in a marked improvement of thefdielectric strength. This phenomenon may apparently be explained by the fact that by increasing the amount of a doping substance effecting the N-conductivity, the doping substance effecting the P-conductivity, i.e. copper, is prevented from entering into the interior of the crystallites and thereby increasing the amount of the P-conductivity effecting doping substance, i.e. copper, in the surface or peripheral layers of the crystallites. Nevertheless, the interior of such crystallites remains sufficiently conductive and substantially improved insulating properties are attained at the crystallite surface.

Other factors tending to influence the ability to incorporate the N-conductivity effecting doping substances (i.e., Bi, Ce, La, Nb, Nd, Pr, Sb, Sm, Ta, etc.) as well as the ability to incorporate the P-conductivity effecting doping substances (i.e., Cu, Fe, Mn, etc.) is the presence of titanium oxides utilized in the production of the ceramic bodies and the type of raw material thereof. Thus, in order to achieve comparably high DK-values and comparably high dielectric strength in the dielectric capacitors of the invention, it is necessary to utilize about 1.5 times more of both of the doping substances if the titanium oxide is utilized in its anatase form rather than in its rutile form.

Curie temperatures of the materials utilized as the dielectric capacitors can be adjusted in a conventional manner. For example, in crystalline structures where strontium or calcium are utilized as the M" metals and tin and zirconium are utilized as the M metals in the aforesaid perovskite crystallite structure, these metals tend to individually and/or jointly function to shift the Curie temperature of the dielectric capacitor material toward a lower temperature. In contrast, the utilization of la lead as a M" metal in the aforesaid perovskite structure functions to increase the Curie temperatures to values above 120 C.

The ability to shift toward lower temperatures in accordance with the principles of the invention affords an added advantage of having the operating temperature range lie below the Curie temperature. For example, if the Curie temperature of a particular composition is 10 C. (such as by inclusion of 20 mol. percent of tin), such as for material having the formula BaO-z(Ti Sn,, .,)O wherein z is a numeral ranging from 1.005 to 1.05, the operating temperature range lies from 0 C. to far in excess of C. The dielectric capacitor bodies of the invention possess, particularly above the Curie temperature, a very high DK-value. Such high DK-values, because of the operating temperature is in the cubical range, simultaneously decrease the loss factor to a very low value and suppress a decrease of the DK-value for ferroelectric substances (achieved by the increased amount of P-conductivity effecting substances, i.e. Cu, Fe, Mn, etc.) in accordance with the Curie-Weiss law. Consequently, such dielectric capacitor materials have a relatively low temperature coefiicient.

The crystallites utilized in the formation of the dielectric capacitor bodies of the invention are preferably formed by intermixing suitable quantities of, for example, BaCO and TiO 5 (Ti0,-is generally derived from and utilized in' its raw ore form, i.ei rutile, anatase, or' mixtures thereof). As will be appreciated, other perovskite starting materials; such as(Ba Pb) Ti 0,; (Ba Ca Ti (Ba Sr) Ti 0,; Pb (Zr Ti) 0,, etc. can also be utilized. The perovskitestarting materials are then intermixed with an N-conductivity'effecting doping substance, such as for example, Sb,0 in amounts ranging from 0.15 to 0.25 percent by weight and with a P-conductivity effecting As a result, it is feasible to utilize a starting or raw material for the production of commercial capacitors in a predetermined procedure or program. Accordingly, tor values can (as in the case of conventional capacitors) be readily attained through appropriate body shaping without the necessity of having to, produce barrier layers on the finished doping substance, such as for example, CuO in amounts ranging from"0.0l to 0.15 percent by weight. This mixture is then generally uniformly pulverized, as by' grinding'ina ball mill for about'l 8 hours while adding about 0.5 mols. of water per mol. of mixture, dried and reacted (a solid-state reaction) at about 950 to 1 100 C.-An important factor in the preparation of the dielectric capacitor crystallites is the uniform initmate mixture of the materials and the attainment of an excess of TiO, (preferably attained through the so-called wet-grinding process described). More generally, (and mother words) it is important to obtain-an excess of about 0.5 to 5 mols. percent of them metals over the M" metals.

However, as will be appreciated; suitable barrier layer capacitor crystallites having substantially equivalent qualities to those previously described may also be attained by utilizing a so-called' dry grinding (or mixing) process. The dry grinding process achieves uniformityof the materials but several excess mols. percent of TiO, must be added to the initial mixture.

'After the completion of the reaction (the solid-state reaction referred to hereinabove), the reaction product is again thoroughly pulverized or ground, such as in a ball mill, with the addition of about 0.5 mols. of water (however, dry grinding is also suitable) per mol. or reaction product for approximately 18 hours'to achieve a fine-sized uniform particle mixture. This mixture is then dried and combined, in conventional manner, with an organic binding agent, such as for example, polyvinyl alcohol. This mixture is then pressed or formed into desired shape orconfiguration. The shaped dielectric capacitor bodies are then subjected to a final sintering operation at about l300 to 1400 C. The completed capacitor bodies (after being provided with appropriate electrodes annealed or evaporated thereon) exhibit the values specified in the tables set forth hereinafter inregard to the dielectric" constant DK, the tg8 (dielectric loss angle) and-the voltage strength.

Aswill be appreciated, an exeeptional'advantage of the invention consists in providing a material having an extremely .flargeapparent DK-value in: a form suitable for capacitor use.

Amspacitorformed from 'su'chniaterials results in'the formation of thin nonconductive layers at the surfaces or peripheries of crystallites, which have a well conducting polycrystalline (a plurality of such crystals bonded together) ceramic body. This is, in contrast to the heretofore known barrier layer capacitors, a quasi-volume capacity I wherein a high dielectric strength is achieved (up-to 100 v./mm. in certain cases).

Further, an additional advantage coupled therewith is that the new capacitor material allows the production of capacitor bodies having extremely small (smallest of all known capaciceramic body through various complicated processes.

Essentially, the material of the invention allows the produc tion of so-called stacking or multilayer capacitors by, for example, applying spraying techniques (or other suitable techniques) to alternately spray thin ceramic layers.(composed of, for example, converted BaTiO, propriate metal oxide doping substances added thereto, such as the previously disclosed CuO and Sb,O, in a suitable liquid or viscous form) on top of one another and subjecting such a stack to a sintering operation-toform a parallelly connected electrical barrier layer capacitor body. I

Referring now to the drawings. FIG. 1 generally illustrates a disc-shaped capacitor body 1. which functions as a dielectric and is produced from the novel material of the invention.

Capacitor coats l2 and 13 are suitably fastened to this material and are provided with suitably fastened external connection means 14 and 15. a 1

FIG. 2 illustrates a tubular-shaped ceramic body 2!. Ceramic body 21 functions as a tubular capacitor and is provided with coatings 22 and 23. OuterIcurrent connection means 24 and 25 are suitably fastened to the coatings 22 and 23 respectively. g Y i FIG. 3 illustrates a monolithic body 31 which is formed from a layer of ceramic materials of theinvention stacked on top of 'one another in a manner conventional to the formation of ceramic bodies. The monolithic block 31 is divided by metallic layers 32and 33 which function as condenser coatings. Layers 32 and 33 are alternatively led to the two connecting sides. Metal coatings 34 and 35 respectively, connect layers 32 and 33 with .oneanother. As will be appreciated, outer connections (not shown) are attached to these outer metal coatings 34' and 35 for connection in a particular circuit. I g i FIG. 4 illustrates a'considerably'enlarged segment IV out of the ceramic bodies illustrated atFlGS. 1+3. The interior of the crystallites have good N-conductivity characteristics. The surface of the peripheral layers 42 are located in surtors) geometric dimensions. This' 'factor is extremely important in current .microtechniqu'e. applications. Forexample, in

utilizing the material of the inventionhaving a DK of 10 (such as one having its Curie point shifted to a lowternperature) can be formed into acapacitor' body'h'avingfor example, 500 pf.

and a dielectric strength of 290 v. (direct voltage) while having a diameter of about Further, the capacitor materia'iof the invention offers a 0.3 and athickness of about 0:2

considerable manufacturing and technology advanlflges in comparison to theheretoforeknown barrier layer capacitor technology. One of the foremost of-such advantages resides in the fact that, for example,'the:metal oxidesnecessary for the production 'of conductive BaTiO, crystalline particles, such as S150; and the metal oxides necessary for theproductio'n of the insulating intermediate orsurface layers, such as CuO can be added directly to the perovskite-starting material (for example, suitable quantities of -BaCO5and TiO,) during the initial I; stage of the formation process.

rounding relationship to the interior 41 of the crystallites and have good P-condcutivity characteristic The tables setforth hereinafter. more clearly illustrate the superior characteristics of the materials of the invention."-

In the divisions of tables [through IV are all substantially identical. The first column enumerates the particular test in sequential order. The second column identifies the form of titanium oxide utilized in the formation of barium-titanate. Columns 3 and 4 specify the amounts of the indicated doping substance utilized. The last threecolumns indicate'the electrical qualities of the particdlarmaterial. The values given are average values attained from measuring-40 bodies in the respective tests. The DK-values'specitied in brackets below :the average DK-valuesrep'resent the highest measured value attained with the highest CuO quantity specified in column 4 for the respective tests. The CuO-quantit'y for the individual tests was varied within the two specified limits. The last column includes a notation".parti ally conductive" to indicate capacitor only to a limited extent. I

A study of the, data in tables l through lV will reveal that for every quantity of doping antim'o'ny',a quantity increase of doping copper results in an increase of thespecific resistance to that these particularmaterials represent a good dielectric an-extremely high value so that such dielectric capacitors possess exceptionally high dielectric strength. Simultaneously with the increase of the doping substances, i.e. copper and antimony, (although other specified N-conductivity effecting and P-conductivity ettectingdoping substance could also be utilized), the value forthe tangent of the loss'angle decreases.

i.e. the loss angle improves. On theotherhand, under the same conditions (i.e. increasing the doping substances), the

individual capaci powder with the ap- DK decreases with the copper additions thereby indicating material 21 indicates that when the amount or quantity of that the insulating layer becomes thicker at the surface of the doping antimony reaches 0.175 percent by weight, the amount crystallites (although such thicker insulating layers are not of copper is 0.05 to 0.06 percent by weight and is so large that visibly detectable). This tendency continues until too much a normal dielectric capacitor si formed, i.e. the. individual doping antimony is present and a normal dielectric capacitor 5 crystallites do not have a conductive core or center with an inis formed, such as for the materials of tests 8 and 25. Test sulating shell but rather insulating throughout.

TABLE I [Materlak BaTiOz, doped with antimony and copper; Tn-l20 C.]

T102- Starting Doping substance Electric qualities measured at 20 C. substance Sb O DK (in percent 000, accordance Specific resistance r by percent by with the given tg 8. 10 (Ohm cm.) weight weight definition) percent Measuring voltage=320 v./mm.

0. 1 0. 040-0. 050 15, 000 85 0.210 partially conductive. 0.1 0. 055 12,000 80 Max. 410 (at 20 v./mm.). 0. 15 0. 02-0. 035 34, 000 60 Max. 840 partially conductive. 0. 15 0. 04-0. 08 28, 000 40 Max. 60-10 0.175 025-0. 035 43,000 (60, 00) 62 40-10 partially conductive. 0. 175 0. 04-0. 05 46, 000 (75, 000) 50 160-10 0.2 0. 045-0. 07 32, 000 (55, 000) 54 80-10 0. 25 0 045-0. 07 2, 000 Like normal capacitor TABLE II [Materialz BaTiOa, doped with antimony and copper; T,.-120 0.]

T1O2- Doping substance Electric qualities measured at 20 0. Starting substance SbzOa, CuO, for the percent percent DK (in accordformation by by ance with the tgoi- S ecific resistance 5 (Ohm cm.) Test Number p31 thfo weight weight given definition) percent easurlng voltage=320 v./mm.

0. 1 0.008 2, 000 100 4-10 (at 20 v./mrn.) partially conductive. 0. 1 0. 011 25,000 120 Max. 3-10 0. 1 0.013 20, 000 100 Max. 7-10 0. 1 0.020 15, 000 55 Max. 3010 0 125 0. 010-0. 013 35,500 70 Max. L10 partially conductive. 0. 125 0. 014-0. 29, 000 60 Max. 3.510 0 125 0. 025-0. 030 14, 000 50 Max. 30-10 0. 0. 015-0. 02 40,000 80 Max. 1.210 partially conductive. 0. 15 0. 022-0. 030 40, 000 40 Max. 15-10 0. 15 0. 035-0. 05 30, 000 30 Max. 30-10 0 175 0. 01-0. 022 47,000 (70, 000) 72 Partially conductive. 0 175 0. 025-0. 045 31, 000 (60,000) 47 170-10 0 175 0. 05-0. 06 3,000 Partially like normal capacitors 0. 0. 035-0. 76 3, 000 Like normal capacitors TABLE III [Materialz B80.Z(T10.74SI10.20)Oz, doped with antimony and copper; T5=40 0.]

T102 Starting Doping substance Electric qualities, measured at 20 C. substance for the 811203, DK (in accordformation percent CuO, ance with the of the by percent by given tg6-10 Test Number BBTIO: weight weight definition) percent Specific resistance r (Ohm cm.)

0. 1 0. 02-0. 05 34,000 (75,000) 48 100-10 (10 v. mm.) 1010* (200 v. mm.). 0. 1 0. 055-0. 085 17,000 (32,000) 54 300-10 (10 v. mm.) 10010 (300 v./mm.). 0.15 0.01 Conductive, no capacitor dielectric properties 0.15 0. 013-0. 025 36,000 (60,000) 65 1-10 (10 v./mm.) partially conductive. 0.15 0. 03-0. 05 41,000 (55, 000 43 20-10 (10 v./mm.) 2.8-10 100 v./mm.) 0.15 0. 055-0. 08 20,000 (35,000) 75 100-10 (10 v./mm.) 2010 (100 v./mm.) 0. 175 0. 01-0. 013 63, 000 (65, 000) 65 Partially conductive. 0.175 0. 015-0. 11 34,000 (62,000) 55 50-10 (10 v./mm.) 9-10 (200 v./mm.)

0. 15 0. 01-0. 015 50,000 87, 000) 53 2-10 (10 v./mm.) partially conductive. 0.15 0. 02-0. 035 26,000 (60,000) 20-10 10 v./mm.), 310 (100 v./mm.) 0. 15 0. 04-0. 055 77,000 (115,000) 50 -10 (10 v./mm.) 4-10 (150 v./mrn.). 0. 15 0. 06-0. 075 48, 000 (95, 000) 100-10 (10 v./mm.;, 12-10 (200 v./mm.). 0. 15 0. 08-0. 10 41,000 (60, 000) 90 400-10 (10 v./mm. 370-10 (150 v./m.m.). 0.175 0. 01-0. 13 78, 000 (80,000) (0.t' -20)-10 (10 v./mm.) partially conductive. 0.175 0. 015-0. 06 66,000 (131,000) 65 10010 (10 v./Inm.), 510 (150 v./m1n.). 0. 175 0. 065-0. 1 49, 000 (85,

500-10 (10 v./1nm.), 55-10 v./mm.).

TABLE IV lMaterial: BaO.z(Tic.sSno.4)Q, doped with antimony and copper; Tn 10 (3.] STIOQ- Doping quantity Average values from 40 measun'ngs; electric qualities. measured at 20 C.

tarting substance ShzO for the forpercent CuO, per- DK (in accordmation of by cent by ance with the tg 6-10 Test Number BaTiOa Weight weight given definition) percent Specific resistance r (Ohm cm.)

0. 1 0. 01 50,000 (80,000) 60 Partially conductive 100- 10 (10 v./n'un.). 0.1 0. 013-0. 055 42, 000 (90,000) 95 100-1. 8 (10 v./n1m.), 3-10 (100 v./mm.). 0.1 0. 06-0. 085 19,000 (46, 000) 120 200- (10 v./mn1.), 8010 (200 v./mm.). 0. 0. 01-0. 045 24, 000 (58, 000) 50 400-10 (10 v./mm.), 4-10 (150 v./mm.). 0.15 0. 05-0. 065 68,000 (115,000) 65 80-10 (10 v./mrn.), 5-l0 (100 v./mm.). 0. 15 0 07-0. 075 46,000 (90,000) 52 15010 (10 v./mm.), 8-10 (50 v./mm.). 0.175 0 10-0. 02 33,000 (55,000) 50 Partially conductive. 0. 175 0 025-0. 08 42, 000 (82, 000) 33 100-10 (10 v./n1m.), 45-10 (100 v./n1m.), 6'10 (200 v./mm.).

0.15 010-0. 1 70,000 (130,000) 70 45-10 (10 v./mm.), 1.5-10 (50 v./mm.). 0.175 0 10-0. 06 11, 000 (60,000) 30 15-10 (10 v./mm 0. 175 0 065-0. 1 68, 000 (120, 000) 75 In addition to the various advantageous control features previously discussed to modify the characteristics of the materials of the invention the graphs of FIGS. 5, 6 and 7 illustrate that the sintering conditions which such materials are subjected to are also a valuable means of controlling or modifying at least certain characteristics of such materials.

The graph illustrated at FIG. 5 shows the DK as a function of the temperature at different sintering conditions. The abscissa specifies the temperature in degrees centigrade while the ordinate specifies the DK (in accordance with the definition given hereinbefore). The material utilized is that of test 6 (identified in the above tables) and is a barium-titanate material (utilizing anatase as the raw material for titanium oxide) having 0.175 percent Sb ll and 0.04 percent CuO as the doping substances therein. The measuring frequency was 1 kHz. Curve 1 represents the DK of this material after it was sintered at 1350 C. for 30 minutes. Curve 2 represents the DK of the material after it was subjected to sintering temperature at 1350" C. for after hour. Curve 3 represents the DK of the material after it was sintered at 1360 C. for 2 hours.

The graph illustrated at FIG. 6 shows the loss factor as a function of the temperature at different sintering conditions. The material tested, the measuring frequency, the sintering temperatures and times are substantially identical to those explained in conjunction with FIG. 5 and, therefore, the reference numerals on the curves are the same as those utilized in FIG. 5.

The graph illustrated at FIG. 7 shows the DK and the tangent of the loss angle 8 on the ordinate as a function of the temperature in degrees centigrade on the abscissa. The material utilized was that of test 50 (identified in the above tables), and has the empirical formula of Ba0-z(Ti,, ,-,Sn,, .,)0 containing 0.15 percent by weight of Sb 0 and 0.03 percent by weight of CuO as the doping substances. The measuring frequency was again 1 kHz. Curve 5 represents the DK trend of the material after it was sintered at 1360 C. for 2 hours. In contrast to this, curve 6 represents the DK trend of the material after it was sintered at 1350 C. for 1 hour. Curve 7 illustrates the trend of the tangent of the loss angle for the material after it was sintered at 13 60 C. forfhoufs and curve 8 illustrates the trend of the tangent of the loss angle for the material sintered at 1350 C. for 1 hour.

The graph illustrated in FIG. 8 also shows the DK and the tangent of the loss angle 5 on the ordinate as a function of temperature in degrees centigrade on the abscissa. The material utilized corresponds to the material of test 46 (identified in the above tables) and has an empirical formula of BaO'z(Ti Sn .,)O containing 0.15 percent by weight of Sb O and 0.06 percent by weight of CuO. The material was subjected to sintering conditions at 1360-C. for 2 hours. Curve 9 illustrates the trend of the DK and curve 10 illustrates the trend of the tangent of the loss angle.

Upon study of the specific resistance (Ohm cm.) of the materials utilized for the graph data in FIGS. 58 it will be seen that the material of test 6 (identified in the above tables) has a specific resistance of 16010 (at ,320 v./mm.); the

100.10 10 v./mn'1.i, 12-10 v./mm.).

material of test 46 (also identified in the tables) has a specific resistance of 8010 8 (at 10 v./mm.) or 5'10 (at 100 v./mm.); and that the material of test 50 (identified in the above tables has a specific resistance of 4510 (at 10 v./mm.) or 1.5-10 (at 50 v./mm. It is therefore apparent that such materials must, necessarily, have a tremendous amount of dielectric strength. Consequently, it will be appreciated that through the principle of the invention an excellent material for barrier layer capacitors is provided which, with the shifting of the Curie temperature toward temperatures below the operating temperature of a particular utility, has a very small and insignificant temperature dependence of the DK.

It will thus be seen that we have provided a novel dielectric capacitor composed of a barium-titanate perovskite material containing at least two different doping substances which meet all of the aforesaid objects.

It will be understood that modifications and variations may be effected on the preferred embodiments disclosed without departing from the spirit and scope of the present invention.

We claim:

1. A dielectric capacitor body composed of a plurality of joined together crystallites to form a ceramic body, said crystallites being composed of a barium-titanate material having a perovskite structure of the formula:

wherein M" is a material selected from the group consisting essentially of Ca, Sr, Pb, Mg, and mixtures thereof; M is a material selected from the group consisting essentially of Zr, Sn and mixtures thereof; x and y are numerals ranging up to one; and z is a numeral ranging from 1.005 to 1.05; said barium-titanate material including at least a first and a second doping substance, said first doping substance predominantly producing N-conductivity in the inside of said crystallites and said second doping substance predominatly producing P-condictivity in the surface layers of said crystallites, said first doping substance being present in amounts ranging from 1.5 to 2.5 times greater than the maximum quantity of the substance necessary for producing maximum conductivity in said barium-titanate material and said second doping substance being present in amounts ranging from 0.01 to 0.15 percent by weight determined on the basis of its oxide.

2. The dielectric capacitor as defined in claim 1 wherein the first doping substance is a material selected from the group consisting essentially of Bi, Ce, La, Nb, Nd, Sb, Sm and Ta and the second doping substance is a material selected from ,the group consisting essentially of Cu, Fe, and Mn.

3. The dielectric capacitor as defined in claim 1, wherein the first doping substance is present in amounts ranging from 0.15 to 0.25 percent by weight, the amount of said first doping substance being calculated on the basis of its oxide.

4. The dielectric capacitor as defined in claim 3, wherein the first doping substance is antimony and the amount thereof is calculated on the basis of Sb2O I 5. The dielectric capacitor as defined in claim 1, wherein the second doping substance is copper and the amount thereof is calculated on the basis of CuO.

6. The dielectric capacitor body as defined in claim 1 wherein the quantity of the quadrivalent perovskite materials is present in amounts ranging from 0.5 to 5 mol. percent greater than the quantity of the bivalent perovskite materials.

7. The dielectric capacitor body as defined in claim 1, wherein the specific resistance of said dielectric capacitor body ranges from about 1.510 to about 50010 8 ohms at 10 v./mm. to 320 v./mm. 1

8 The dielectric capacitor body as defined in claim 1, wherein the dielectric constant-value of said dielectric capacitor body ranges from about 10 to 13-10".

9. The dielectric capacitor body as defined in claim 1 wherein the quantity of TiO is present in amounts ranging from 0.5 to 5 mol. percent greater than the quantity of the bivalent perovskite materials.

10. The dielectric capacitor body as defined in claim 1 wherein the quantity of TiO. is present in amounts ranging from 0.5 to 5 mol. percent greater than the quantity of BaO.

11. A dielectric capacitor body composed of a polycrystalline ceramic body the crystallites composing said body consisting essentially of a barium-titanate perovskite material having the formula:

wherein z is a numeral ranging from 1.005 to 1.05, said barium-titanate material including about 0.15 percent to 0.25 percent by weight Sb O predominantly producing N-conductivity in the inside of said crystallites and about 0.01 to 0.15 percent by weight of CuO predominantly producing P-conductivity in the surface layers of said crystallites.

12. The method of producing a dielectric capacitor body comprising: (1) forming a barium-titanate crystallite having a perovskite structure of the formula:

wherein M" is selected from the group consisting essentially of Ca, Sr, Pb, Mg and mixtures thereof; M" is selected from the group consisting essentially of Zr, Sn and mixtures thereof; x and y are numerals ranging up to one, and z is a numeral ranging from 1.005 to 1.05; (2) admixing at least a first and a second doping substance to said crystallites to achieve a substantially uniform intimate mixture thereof, said first doping substance predominantly producing N-conductivity in the inside of the crystallites, said second doping substance predominantly producing P-conductivity in the surface layers of said crystallites; (3) heating said mixture to a temperature in the range of 950 C. to 1100 C. to achieve a solid-state body reaction thereof; (4) uniformly pulverizing the reacted mixture; (5) mixing an organic binder with such pulverized mixture; and (6) forming a capacitor body thereof and subjecting said body to sintering conditions at temperatures in the range of 1300 C. to 1400 C. for a period of time ranging from about 30 to minutes.

13. The method as defined in claim 12, wherein 12, wherein the step (1) comprises uniformly intermixing an amount of BaCO and an amount of H0 in excess of the aforesaid BaCO amount, said excess amount being in the range of 0.5 to 5 mol. percent.

14. The method as defined in claim 13, wherein the first doping substance is a material selected from the group consisting essentially of Bi, Ce, La, Nb, Nd, Pr, Sb, Sm and Ta and the second doping substance is a material selected from the group consisting essentially of Cu, Fe, and Mn.

15. The method as defined in claim 14, wherein the first and second doping substances are in their respective oxide forms.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 569, 802 Dated March 9, 1971 I Horst Brauer and Renate Kuschke PAGE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 5, "pervoskite" should read--perovskite-;

line 6, Ba XM yO-Z (Ti M o shodd read-- (Ba M O-z (Ti M y) 0 line 10, "M II" should read--M Column 3, line 7, Ba XM O'z) Ti yM 0 should ree ll IV (Ba M 0 z (T1 yM 0 line 45, cancel "and are" and. insert therefore-consta peculiar--.

Column 4, line 52, cancel "la";

line 61, "BaO-z (Ti Sn 0 should read--BaO'z Ob OA 2"" Column 5, line 20, "m should read--M Column 8, line 4, "Si" should read--is--.

Column 9, TABLE IV, TEST NUMBER 43, column s, "1001.

should read--l00-l0 UNITED STATES PATENT OFFICE contd CERTIFICATE OF CORRECTION Patent No. 3 559302 Dated March 9, 1971 Inveritofls) Horst Brauer and Renate Kuschke PAGE- 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

TEST NUMBER 48, column 3, "0.l0-O.(

should read--0.0l-0.02--;

TEST NUMBER 50, third column, "0.10-

should read--0.0l-O.1-.

Column 9, line 36, "at" should read.--of--;

line 37, cancel "2 hours" and insert therefore-1 hour Curve 4 represents the same material after sintering at 1360 C.

2 hours--;

line 69, "at" should read--of--.

Column 10, line 20, "80 10 8" should read-8010 line 21, after "tables" insert--)--;

line 45, "(Ba ll 0-2 (Ti M 0 should read--(B n 1v M X) 0 Z (T1 M y) 0 Column 11, line 10, "500-10 8" should read-60010 Column 12 line 3 "Ba XM b O-z (Ti yM (0 should rea (Ba M o-z (Ti M 0 line 23, cancel "12, wherein".

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 569, 802 Dated March 9, 1971 Inventor(s) Horst Brauer and Renate Kuschke PAGE 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 53, "if" should readis";

line 66, "20.lO "should read--20'10 Column 3, lines 44-45, "(dielectric and are" should read--(diele constant) peculiar--;

line 56, "mp" should read--pm--;

line 57, "mp (millimicrons)" should read-11m (microns) Column 5, line 15,"initmate" should read--intlmate--;

line 20, "m should ream-M Column 6, line 46, "condcutivity" should read--conductlvity--.

Column 9, line 36, "after" should read-one--.

Signed and sealed this 18th day of January 1972 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Pa

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Classifications
U.S. Classification257/43, 361/434, 29/25.2
International ClassificationC04B35/462, H01B3/02, H01G4/12, C04B35/468
Cooperative ClassificationH01G4/1281, C04B35/4684, H01B3/025
European ClassificationH01B3/02Z, H01G4/12E2, C04B35/468B2