HK1062955B - Method for making a multilayer ceramic capacitor and multilayer ceramic capacitor produced therefrom - Google Patents

Description

Method of manufacturing multilayer ceramic capacitor and multilayer ceramic capacitor manufactured thereby

The present invention is a divisional application of the chinese patent application entitled "magnesium zinc titanate powder containing barium lithium borosilicate flux and multilayer ceramic COG capacitors made therefrom" having application number 01125263.4, application date 8/27/2001.

Technical Field

The invention relates to a multilayer ceramic capacitor which meets the COG standard and contains a ceramic dielectric based on magnesium zinc titanate mixed with a glass containing a sintering flux, the mixed material being capable of sintering and curing at temperatures well below 1100 ℃, and to a method for the production thereof.

Background

The capacitance variation of temperature stable ceramic capacitors meeting EIA standards, COG (a.k.a.npo), over the temperature range from-55 ℃ to 125 ℃ must be kept within +/-30 ppm. Such capacitors must also have a quality factor Q of greater than 1,000 at 1 mhz, a quality factor greater than 1000 corresponding to a Dissipation Factor (DF) of no greater than 0.01. The ceramic precursor powder has been fired under conditions to obtain a 95% theoretical density of the cured ceramic which is well suited as such a high quality dielectric ceramic. Sintering of high sintering temperature ceramic precursor materials such as magnesium zinc titanate is typically accomplished at temperatures of 1100 ℃. It is known to lower the sintering temperature required for producing a cured dielectric ceramic by adding a small amount of a glass containing a flux as a sintering aid to a high-temperature fired (high-firing) ceramic powder. Examples of COG ceramic compositions that can be sintered at about 1100 c are disclosed in U.S. patent No. 4,882,650, published 11/11 1989 and U.S. patent No. 4,533,974, published 6/8 1985.

In the manufacture of a multilayer capacitor (MLC), a number of metal laminar electrodes are respectively sandwiched between successive layers of green precursor ceramic powder containing flux, if any. Thus, metal electrodes buried in green (unsintered) ceramic are necessarily subjected to temperatures high enough to sinter the ceramic to maturity. The most common material formulation for metal electrodes is 70 wt% Ag and 30 wt% Pd. The alloy of this composition has a melting temperature of 1150 c and is typically used for MLC capacitor electrodes that are heated to temperatures no higher than 1140 c to avoid the risk of metal melting and flowing out. When using sintering furnaces, which cannot maintain the temperature within a deviation of 10 c, it is necessary to use furnaces set at lower temperatures, a safety factor of 10 c being further generally adopted when manufacturing MLCs.

The addition of larger amounts of sintering flux lowers the MLC sintering temperature, but at the expense of lower dielectric constant (K) and lower other performance criteria such as Q. There are relatively few known raw material formulations that can be sintered to high density ceramic precursors plus fluxes at temperatures below about 1100 c, and even less of such raw material powder mixtures are in practical use in the industry because the formulations and sintering conditions are more severe, resulting in lower yields.

The cost of palladium is an order of magnitude higher than the cost of silver, and palladium is generally the largest factor in the cost of manufacturing MLC capacitors. One approach to replacing palladium in a buried electrode is to use a base metal such as nickel and/or copper. With base metal electrodes, however, sintering must be carried out at temperatures below the melting point of the base metal (1453 ℃ for nickel and 1083 ℃ for copper). And sintering must be performed in an atmosphere with little oxygen, which greatly complicates the process. The control of the atmosphere having a low oxygen pressure itself raises costs, and there is a great limit to the selection of a ceramic composition which does not become semiconductive by losing oxygen at the time of sintering in order to obtain specific dielectric ceramic properties.

The flux used in many air-fired MLC capacitors contains oxides of bismuth, cadmium and lead which are particularly effective at lowering the melting point of the flux. This advantageously further reduces the sintering temperature for a given amount of flux. However, these oxides tend to lower the Q of MLC capacitors, and bismuth reacts with silver palladium electrodes, making the quality factor even worse. These volatile heavy metal oxides also contaminate the sintering furnace, producing sintering results that are less than regular. Perhaps most importantly, they pose a risk to the environment, especially the health of personnel in the field of manufacturing ceramic powders and MLC capacitors.

It is therefore an object of the present invention to provide a ceramic powder for manufacturing a multilayer ceramic capacitor complying with the COG standard, which raw material powder can be sintered to be aged at a temperature of 1000 ° +/-50 ℃ in an air atmosphere, so that MLC can be used with electrodes having a higher silver content and a lower content of expensive components, such as 85% Ag/15% Pd.

It is a further object of the present invention to provide a ceramic powder comprising a high temperature fired portion comprised of magnesium zinc titanate and a low temperature sintering flux portion substantially free of harmful heavy metal oxides of lead, bismuth and cadmium.

Disclosure of Invention

A dielectric ceramic powder mixture is composed mainly of aggregated particles each of which is formed by uniformly combining two kinds of powder particles by mild calcination and surface co-reaction. One of the two powders is a high temperature fired ceramic precursor powder which is magnesium zinc titanate, and is 87-98 wt% of the dielectric ceramic powder mixture. The other is a powdered barium lithium borosilicate sintering flux, which is 2-13 wt% of the dielectric ceramic powder mixture.

The magnesium zinc titanate powder is preferably a fully reacted compound Mg_2/3Zn_1/3TiO₃Where up to 20 mol% of Mg may be replaced by an equimolar amount of an alkaline earth metal, and when only barium is substituted, up to 60 mol% may be substituted.

A particularly effective composition range for the barium lithium borosilicate flux is 10-55 wt% Li₄SiO₄3-40% by weight of BaO.B₂O₃And 10-76 wt% of 3 BaO. B₂O₃. Another preferred fluxing agent composition range is 22-26 weight percent Li₄SiO₄20.5 to 23.5 wt% of BaO. B₂O₃And 50-56 wt% of 3 BaO. B₂O₃。

The dielectric ceramic powder mixture is prepared by mixing 87-98 wt% magnesium zinc titanate and 2-13 wt% powdered barium lithium borosilicate sintering flux to form a uniform powder mixture; the mild calcination was carried out at a temperature of 600-750 ℃ to obtain a powder consisting of aggregated particles of a homogeneous powder mixture, wherein each aggregated particle has substantially the same composition of magnesium zinc titanate and barium lithium borosilicate as in the overall powder. The mildly calcined agglomerate grains may then be comminuted to render the dielectric ceramic powder mixture a free-flowing powder having an average agglomerate grain size of about 1.2 microns.

A method for manufacturing a multilayer ceramic capacitor requires preparation of a slurry by grinding the above dielectric ceramic powder mixture in an organic vehicle to form a slurry layer and then drying. A first patterned palladium-silver alloy film was deposited onto a dried layer. At least a second green ceramic layer is then placed on the first patterned alloy film to obtain a stack. A second patterned alloy film is deposited on the second green ceramic layer, and at least a third green ceramic layer is deposited on top of the second patterned alloy film. The stack is then sintered at a temperature in the range 950-. The silver paste is thermally cured to form terminations in contact with both the first and second alloy layers. A nickel film was then electroplated over the cured silver termination.

This results in a multilayer ceramic capacitor comprising a dense, cured ceramic body comprising 87-98% by weight of magnesium zinc titanate, a fully reacted compound Mg, and 2-13% by weight of a powdered barium lithium borosilicate sintering flux, and at least one layer of layered electrode embedded in the ceramic body_2/3Zn_1/3TiO₃Wherein up to 20% of said Mg is substituted by an equimolar amount of an alkaline earth metal. The embedded electrode may be comprised of an alloy of silver and palladium, wherein the silver content is at least 80% by weight. The present invention recognizes that in fabricating a COG type MLC capacitorThe reduction in the required sintering temperature of the ceramic allows for the embedding of electrodes with increased silver content, and MLC capacitors with such higher conductivity embedded electrodes will exhibit higher Q values. This is particularly true for COG MLC capacitors where the Q depends more on the electrode resistivity and less on the intrinsic Q of the dielectric ceramic itself, so that the benefit of a lower sintering temperature of the COG multilayer capacitor can result in lower manufacturing costs and better COG performance.

The present invention also recognizes that the inclusion of lithium in the flux portion of the ceramic powder can lower the melting temperature of the flux and can unexpectedly reduce the occurrence of failures in the life test of multilayer COG capacitors.

The above object of the present invention can be achieved by using the above magnesium lithium borosilicate sintering flux. The above object of the present invention has been exceeded in the sense that MLC capacitors can be produced using the starting powder according to the invention and sintering at a temperature in the range of about 940 ℃ and 1100 ℃.

Drawings

Fig. 1 shows a side sectional view of a disk-shaped ceramic capacitor.

Fig. 2 shows a side cross-sectional view of a multilayer ceramic (MLC) capacitor with buried electrodes.

Detailed Description

A test disc-shaped ceramic capacitor was manufactured in which the high-temperature-fired component of the raw material powder was magnesium zinc titanate. These test disc capacitors were made as shown in fig. 1. A thin dielectric ceramic disk 10 has electrodes 11 and 12 bonded to opposite major surfaces of the disk capacitor. Disc capacitors are much easier to manufacture than multilayer capacitors, and all other criteria for a disc capacitor's specific composition and sintering conditions, except for the DF and Q performance criteria, are useful criteria for the performance that can be obtained from a corresponding multilayer capacitor using the same raw powder composition.

Production of raw ceramic powder

One method of making a ceramic powder raw material mixture begins with preparing a high-temperature fired powder mixture having an average particle size of about 1.0 micron by combining 96-98 mole percent of some precursor material of stoichiometric Magnesium Zinc Titanate (MZT), wherein up to 4 mole percent of the magnesium may be substituted by calcium. This can be achieved by replacing a portion (e.g., 2.9 mole%) of the magnesium titanate with an equimolar amount of calcium titanate. Likewise, other such partial substitutions of magnesium, such as equimolar amounts of barium oxide or barium zirconate, may be employed to adjust the TCC of the sintered powder capacitor body. In the case of barium zirconate, it may be used instead of an equimolar amount of magnesium titanate. The amount of substitution of barium in the magnesium zinc titanate may be as high as 60 mole percent as described in the above-mentioned U.S. Pat. No. 4,882,650.

A second low-melting glass-forming substance-containing powder is added to the high sintering temperature ceramic powder. The low melting powder is used as a sintering flux and is composed of oxides of barium, boron and silicon or their equivalents.

The powder mixture was then milled to a homogeneous powder mixture and then mildly calcined at a temperature of about 600 c to obtain a powder consisting of aggregated particles of the powder mixture, wherein each aggregated particle had substantially the same composition as the homogeneous precursor powder mixture and the average size of the aggregated particles was about 1.2 microns.

Manufacturing a disc capacitor

The method for manufacturing a disc capacitor such as that shown in fig. 1 is as follows. The raw powder mixture was pressed to a thickness of about 35 mils (0.89 mm) in a half inch (12.7 mm) diameter die at a pressure of 15,000 psi. The resulting round green discs were then sintered at 1100 deg.C (unless otherwise stated below) for 3 hours. After cooling, a silver paste was applied to the two opposite surfaces of each sintered disc 10, and the discs were subsequently heated to 800 ℃ to solidify the electrodes 11 and 12.

In some embodiments the predominant composition of the high-temperature-fired raw material powder is Mg_2/3Zn_1/3TiO₃In which an equimolar amount (e.g. 2.9 mol%) of magnesium is replaced by a small amount of calcium. In other embodiments, only some BaZrO is added₃. Such substitution or addition of alkaline earth metals in magnesium zinc titanate can be advantageously used to adjust the Temperature Coefficient of Capacitance (TCC) of a sintered disc capacitor. Manganese carbonate, about 0.01 wt%, is also added and is typically used to improve the service life test performance of many different types of dielectric ceramic formulations. Powdered barium borosilicate sintering flux was also added to the raw material mixture.

Referring to tables I and II, a two-component flux of barium borate and zinc silicate was effective when sintering the dielectric ceramic powder in the temperature range of 1100-1150 deg.C, except for example 6a in Table II. Only 0.5% by weight of 3 BaO. B was used₂O₃And 1.0 wt.% Zn₂SiO₄The fired capacitor produced very high densities and had a K value of 23 or 24.

Furthermore, the TCC values are within the COG criteria. In addition, the value of DF is very low, especially in examples 3, 4 and 7. These capacitor embodiments have a Q factor of at least 10,000. Although example 2 (from 1.2 wt% 3 BaO)₂·B₂O₃And 1.0 wt.% Zn₂SiO₄Prepared) and example 6a did not achieve cure, while the same formulation fired at 1150 c achieved cure and the initial performance was somewhat good.

In testing the MZCTs of examples 1-6 b containing the barium borate and zinc silicate two-component sintering flux, it was found that the fired capacitor failed the life test. As shown in Table II, several different additives were used in order to extend the useful life, but without effect, although some additives are well known and have been used to extend the useful life (BaCO)₃、BaZrO₃、MnCO₃And Y₂O₃). These are shown in Table II as examples 1 to 6bThe capacitor failed the life test.

When a small amount of lithium carbonate (0.3 wt%) was tested to see if it would affect the service life, the effect of lithium carbonate was quite unexpected. As shown in Table I and II for example 7, those containing Li₂CO₃The capacitor of (a) passes the service life test and still has excellent electrical and linear properties. Subsequently, Li was tested₂SiO₄The effect on the service life. As shown in Table I and II, example 8, with Li₂CO₃In contrast, those containing Li₂SiO₄The capacitor passes the service life test and achieves good electrical and linear performance. Example 8 has a lower Q factor than example 7, probably due to its lower sintering temperature of 1,110 ℃. Examples 7 and 8 are both within the COG standard.

Magnesium zinc calcium titanate-containing barium lithium borosilicate flux

A series of test disc capacitors were fabricated in which the composition of the raw material powders was 90 weight percent of the above-described magnesium zinc calcium titanate and 10 weight percent of the lithium silicate barium borate flux.

Referring to Table III, the first group A of the experimental disc capacitors (i.e., examples 9-12) contained a mixture of 1 mole of lithium silicate (Li)₄SiO₄) 3 mol of barium perborate (3 BaO. B)₂O₃) And 1 mol of barium borate (BaO. B)₂O₃) The flux is composed of raw material powder. As shown in the other three columns of table III, the composition of the flux in each example may be expressed as a weight% of the total flux. Each embodiment has 4 disc capacitors. The 4 disc capacitors of example 9 were sintered at 1000 c and the capacitor of example 10 was sintered at 975 c. The capacitor of example 11 was sintered at 950 ℃ and the capacitor of example 12 was sintered at 925 ℃ as shown in Table III.

The flux compositions (B, C, D, E, F, G, H and I) for the second through ninth sets of test disc capacitors, examples 13-16, 17-20, 21-24, 25-28, 29-32, 33-36, 37-40, and 41-44, respectively, are similarly shown in the middle six columns of Table III.

After sintering and cooling, the Dissipation Factor (DF), the dielectric constant at room temperature (K) at 23 ℃ and the Temperature Coefficient of Capacitance (TCC) measured at-55 ℃ and +125 ℃ were measured for 4 disc capacitors in each example, expressed as a percentage change in K, and the 4 values obtained were averaged. These data are presented in the last five columns of table III.

None of the samples obtained after firing the nine compositions at 925 c was dense and cured and was porous. It can further be seen that the capacitors of examples 9 and 10, having a group a raw powder composition and sintered at 1000 ℃ and 975 ℃, did not meet the TCC requirements of the COG standard; the requirement is that the dielectric constant (K) at-55 ℃ or +125 ℃ does not vary by more than 30% of the room temperature K value. Capacitors made from group F (corresponding to examples 17, 21, 25 and 29) and C, D, E sintered at a higher temperature of 1000 ℃ also failed this TCC requirement of the COG standard. For all examples that were densified after firing, including at least two of the compositions of groups A through I, the dielectric constant ranged from 21 to 23, which is typical of COG capacitors of the prior art that were typically fired at 1100 ℃ and above, and all nine of the test compositions herein that were cured after firing had satisfactory K values. However, as can be seen from the capacitor properties listed in Table III, certain raw powder formulations such as G, H and group I sintered in ranges including 1000 deg.C, 975 deg.C and 950 deg.C provided unusually good performance in compliance with the COG standard. Moreover, all of the raw powder composition formulations listed in Table III provide COG-compliant properties after sintering at a temperature in the range including 975 ℃ and 950 ℃.

The effect of the method of providing conductive terminations across the MLC capacitor body on the performance specified by the COG standard

Multilayer ceramic (MLC) capacitors were fabricated by the following prior art method and the effect of the method of applying the electrical terminations of the capacitors on the performance specified by the COG standard was evaluated.

The raw material powder mixture is ground in a liquid organic vehicle to produce a slurry. A layer of the slurry is applied to a flat substrate and then dried. A layer of palladium-silver ink was screen printed in a pattern over the dried layer of ceramic paste.

Additional layers of ceramic slurry and electrode paste are applied by curtain coating or tape processing as described above, and the resulting patterned film of palladium-silver ink is deposited between successive adjacent ceramic layers, respectively, to obtain a stack of dry "green" ceramic layers with the patterned electrode layer sandwiched therebetween.

As shown in fig. 2, the multilayer capacitor body 20 has a number of ceramic layers 21 and a number of buried electrodes 22. The portion cut from the stack is also temporarily a green ceramic body which is heated to remove organic components and harden it for sintering.

Referring to Table IV, a series of MLC capacitor bodies of examples 45, 46, 47, 48, 49, 50, 51, 52 and 53 were fabricated using the above-described method, wherein the high-temperature-fired raw material powder was the same Magnesium Zinc Calcium Titanate (MZCT) as in examples 1-8, but with the addition of a step of introducing a termination. Different MZCT contents, different sintering temperatures and different methods of introducing terminals in the raw powder are adopted.

One common method of depositing solderable conductive terminations onto opposite ends of the electrode layers of a multilayer ceramic capacitor requires applying a silver paste to both ends of the capacitor body 20 (fig. 2) where a set of alternately arranged buried electrodes are exposed and heating at 750 c for a few minutes to form silver terminations 25 and 26. However, particularly for COG MLC capacitors, it is known to take steps of electroplating a nickel barrier layer over the silver terminations and then applying a tin-lead solder layer over the nickel layer. This provides a low resistance and a more reliable connection between the end of the buried electrode and the silver termination layer. The termination thus provided allows for easier surface mounting of the capacitor to a circuit board.

The method of introducing terminations may be varied so that the required nickel plating and solder application steps are not used in some of these tests, the data for which are also set forth in table IV. After the capacitors were cooled to room temperature, terminals were introduced by applying a silver paste directly to both ends of a sample group of these sintered capacitors and then heating to cure. The capacitance of the sample set of capacitors was measured (to calculate the dielectric constant, K), the Dissipation Factor (DF), and the TCC. The remaining sintered bodies were nickel plated and solder coated and then subjected to a life test in which a 300 volt dc voltage was applied between the two terminals to a dielectric thickness of 12-15 volts/micron while the capacitor temperature was maintained at 125 c. If the capacitor insulation resistance decreases by two orders of magnitude from the initial value within the first one hundred hours of the life test, the capacitor is considered to have failed the life test.

The silver terminations of the MLC capacitors in examples 45, 47, 49 and 52 of table IV were all nickel plated and solder coated, whereas the capacitor terminations of examples 46, 48, 50, 51 and 53 were not subjected to these processes. It can be seen that the capacitors of examples 45, 46 and 47 have the same ceramic composition, i.e., containing 10 wt% flux (the same flux as in group C of table III), but the nickel electroplated capacitors of examples 45 and 47 failed the life test regardless of their sintering temperatures. However, the capacitors of the remaining examples 48 to 53 passed the service life test regardless of whether they were previously subjected to nickel plating; these capacitors all contain 5 wt% or 7.5 wt% flux. Larger amounts of flux jeopardize the life test of the COG capacitor, which is otherwise well performing. Therefore, when nickel plating is to be performed on both ends of the silver-coated MLC capacitor, it is preferable to use less than 8 wt.% of the barium lithium borosilicate flux in the MLC capacitor of the invention.

As can be seen from the data presented in tables III and IV, the COG capacitor can be fabricated using a larger amount of barium lithium borosilicate flux, which results in buried electrodes containing much less palladium than the conventional 70% Ag/30% Pd alloy.

The effect of different amounts of barium lithium boro-silicate flux on the performance specified by the COG standard-

A series of MLC capacitors were produced using a raw powder mixture in which the amount of flux varied from 0 to 12 wt% and the sintering temperature varied from 950 ℃ to 1130 ℃. These variables are listed in table V, along with the corresponding experimental data. For this series of test capacitors, Mg was used as the raw material powder_2/3Zn_1/3TiO₃2.9 wt% CaO was added, and the flux consisted of 22.61 wt% BaO.B₂O₃53.23% by weight of 3 BaO. B₂O₃And 24.16 wt.% Li₄SiO₄And (4) forming. It is demonstrated here that these materials can be sintered to cure at any temperature in the range of 950 ℃ to 1130 ℃ using an appropriate amount of flux. Examples 62, 63, 64 and 64, which used a large amount of flux (10-12 wt%), provided excellent performance as specified by the COG standard. Examples 59-61 using medium amounts of flux (5-8 wt%) were also very good. Example 58 shows that at a flux level of 5 wt%, the sintering temperature of 1000 c is too low for the raw powder to react completely and achieve cure. Examples 54-57, all fired at 1130℃, sintered and produced good dielectric bodies, but did not meet the TCC limit of the COG standard. It is believed that the substitution of a small amount of barium titanate for calcium titanate in magnesium zinc calcium titanate would likely bring the TCC performance closer to the limits of the COG standard. However, it is believed that the present invention is limited to the inclusion of the fluxing agent in an amount of no less than 2 weight percent, excluding the formulation of example 56.

TABLE Ia

Magnesium Zinc Calcium Titanate (MZCT)

Oxide compound	By weight%	Mol% of
			MgO	18.66	31
ZnO	18.84	15.5
			CaO	2.89	3.5
TiO	59.6	50

Claims (10)

1. A method of manufacturing a multilayer ceramic capacitor comprising:

a) making a slurry by milling a dielectric ceramic powder mixture consisting essentially of agglomerated particles, each of said agglomerated particles being formed by uniformly combining two powder particles by mild calcination and surface co-reaction to form agglomerated particles, said two powder particles in each of said agglomerated particles consisting of 87 to 98 weight percent of a magnesium zinc titanate powder and 2 to 13 weight percent of a powdered barium lithium borosilicate sintering flux, respectively, in an organic vehicle;

b) forming layers of said slurry, drying the layers, depositing a first patterned palladium-silver alloy film onto one of said dried layers;

c) depositing at least a second green ceramic layer on the first patterned alloy film to form a stack, depositing a second patterned alloy film on the second green ceramic layer, and forming at least a third green ceramic layer on the second patterned film;

d) sintering the stack at a temperature in the range of 950 ℃ and 1120 ℃ to form a dense cured ceramic body;

e) applying a silver paste to both end faces of the ceramic body to which the edges of the first and second layer gold pattern layers extend;

f) heating the stack to cure the silver paste to form terminals in contact with each of the first and second gold layers.

2. The method of making a multilayer ceramic capacitor according to claim 1, further comprising applying a nickel layer over said cured silver terminations by electroplating.

3. A multilayer ceramic capacitor comprising a dense, cured ceramic body and at least one layer of layered electrodes embedded within said ceramic body, said at least one layer of electrodes extending onto one end of the ceramic body, said ceramic body and said embedded electrodes being co-fired; the ceramic body is composed of 87-98 wt% magnesium zinc titanate and 2-13 wt% powdered barium lithium borosilicate sintering flux.

4. The multilayer ceramic capacitor of claim 3 wherein said at least one buried electrode is an alloy of silver and palladium wherein said silver is present in an amount of at least 80 weight percent.

5. The multilayer ceramic capacitor of claim 3 wherein said barium lithium borosilicate flux is made from 10-55 wt.% Li₄SiO₄3-40 wt% of BaO. B₂O₃And 10-76 wt% of 3 BaO. B₂O₃And (4) forming.

6. The multilayer ceramic capacitor of claim 3 wherein said barium lithium borosilicate flux is comprised of 22-26 wt.% Li₄SiO₄20.5 to 23.5 wt% of BaO. B₂O₃And 53.2 to 56% by weight of 3 BaO. B₂O₃And (4) forming.

7. The multilayer ceramic capacitor of claim 3 wherein said magnesium zinc titanate powder is the fully reacted compound Mg_2/3Zn_1/3TiO₃。

8. The multilayer ceramic capacitor of claim 3 wherein said magnesium zinc titanate powder is Mg_2/3Zn_1/3TiO₃Up to 20 mole% of the Mg is replaced by an equimolar amount of an alkaline earth metal.

9. The multilayer ceramic capacitor of claim 8 wherein said alkaline earth metal is selected from the group consisting of calcium, strontium, barium and combinations thereof.

10. The multilayer ceramic capacitor of claim 3 wherein said magnesium zinc titanate powder is Mg_2/3Zn_1/3TiO₃Up to 60 mole% of the Mg is replaced by an equimolar amount of barium.