# US 6,723,673 B2 · High dielectric constant very low fired X7R ceramic capacitor, and powder for making

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- Number: US 6,723,673 B2
- Document ID: US6723673B2
- Status: Granted
- Kind: B2
- Application number: 10/409,808
- Filed: 2003-04-09
- Published: 2003-10-30
- Granted: 2004-04-20
- Earliest claimed: 2000-08-31
- Assignees: MRA Laboratories, Inc.
- Inventors: Galeb H. Maher; Samir Maher; James M. Wilson
- Web page: https://patentgrep.com/patent/US6723673B2

## CPC

- C04B 35/6303: {Inorganic additives}
- C04B 35/468: based on barium titanates
- C04B 35/4682: {based on BaTiO3 perovskite phase}
- H01G 4/1227: {based on alkaline earth titanates}
- B32B 2311/08: Silver
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3224: Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3236: Alkaline earth titanates
- C04B 2235/3251: Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof
- C04B 2235/3262: Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
- C04B 2235/3275: Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
- C04B 2235/3279: Nickel oxides, nickalates, or oxide-forming salts thereof
- C04B 2235/3281: Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
- C04B 2235/365: Borosilicate glass
- C04B 2235/408: Noble metals
- C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron
- C04B 2235/77: Density
- C04B 2235/785: Submicron sized grains, i.e. from 0,1 to 1 micron
- C04B 2237/346: Titania or titanates
- C04B 2237/408: Noble metals, e.g. palladium, platina or silver
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM

## Abstract

The invention includes a dielectric ceramic powder mixture comprising at least ninety weight percent essentially pure barium titanate powder having an average particle size of from 0.2 to 1.2 microns; from 0.2 to 2.5 weight percent of barium lithium borosilicate flux; from 0.1 to 0.3 weight percent of MnCO3; a grain growth inhibitor such as niobium oxide or other niobate compound; and, 0.4 to 1.2 weight percent of an additive selected from the group consisting of a rare earth oxide, yttrium oxide, a combination of rare earth oxides, and a combination of yttrium oxide and rare earth oxides, such that ions of the additive(s) have an average ionic radius of about 0.97 angstroms. The dielectric ceramic powder provides a start powder for making very low firing multilayer ceramic capacitors satisfying X7R performance requirements.

## Claims

### Claim 1

A dielectric ceramic start powder comprising:
a. at least ninety weight percent essentially pure barium titanate powder having an average particle size of from 0.2 to 1.2 microns;
b. from 0.2 to 2.5 weight percent of a flux selected from the group consisting of barium lithium borosilicate flux, zinc lithium borosilicate flux, and mixtures thereof;
c. from 0.05 to 0.3 weight percent of MnCO3;
d. a grain growth inhibitor selected from the group consisting of niobium compounds Nb2O5, BaNb2O6, CaNb2O6, MgNb2O6, LiNbO3, and mixtures thereof such that a weight percent of Nb2O5 ranges from 0.4 wt % to 1.50 wt %, and tantalum compounds, and mixtures thereof, such that a weight percent of Ta2O5 ranges from 0.66 wt % to 2.50 wt %, and a mixture of molar equivalents of the niobium and tantalum compounds; and,
e. from 0.4 to 1.4 weight percent of an additive selected from the group consisting of a rare earth oxide, yttrium oxide, a combination of rare earth oxides, and a combination of yttrium oxide and rare earth oxides, such that ions of the rare earth oxide, ions of the yttrium oxide, ions of the combination of rare earth oxides, and ions of the combination of rare earth oxides and yttrium oxide have an average ionic radius of about 0.97 angstroms.

### Claim 2 (depends on 1)

The dielectric ceramic start powder of claim 1, wherein the flux is about 1.0 weight percent of the barium lithium borosilicate flux.

### Claim 3 (depends on 1)

The dielectric ceramic start powder of claim 1, further comprising from 0.01 to 0.4 weight percent silver.

### Claim 4 (depends on 1)

The dielectric ceramic start powder of claim 1, wherein the barium lithium borosilicate flux is about 50 molar % Li4SiO4, 25 molar % BaO.B2O3, and 25 molar % 3BaO.B2O.

### Claim 5 (depends on 1)

The dielectric ceramic start powder of claim 1, further comprising from 0.01 to 0.4 weight percent copper.

### Claim 6 (depends on 1)

The dielectric ceramic start powder of claim 1, further comprising about 0.05 to 0.3 weight percent MnCO3 and about 0.01 to 0.25 weight percent Co3O4.

### Claim 7 (depends on 1)

The dielectric ceramic start powder of claim 1, wherein the grain growth inhibitor consists essentially of Ta2O5.

### Claim 8 (depends on 1)

The dielectric ceramic start powder of claim 1, wherein the additive is a combination of rare earth oxides including about 0.2 weight percent Ho2O3 and 0.8% Gd2O3, and about 0.1 weight percent silver.

### Claim 9

A method of manufacturing a dielectric ceramic start powder, comprising the steps of:
a. intensively wet milling from 0.2 to 2.5 weight percent of barium lithium borosilicate flux, from 0.05 to 0.3 weight percent of MnCO3, from about 0.01 to 0.25 weight percent Co3O4, a grain growth inhibitor selected from the group consisting of niobium compounds Nb2O5, BaNb2O6, CaNb2O6, MgNb2O6, LiNbO3, and mixtures thereof such that a weight percent of Nb2O5 ranges from 0.4 wt % to 1.50 wt %, and tantalum compounds, and mixtures thereof, such that a weight percent of Ta2O5 ranges from 0.66 wt % to 2.50 wt %, and a mixture of molar equivalents of the niobium and tantalum compounds; and, from 0.4 to 1.2 weight percent of an additive selected from the group consisting of a rare earth oxide, yttrium oxide, a combination of rare earth oxides, and a combination of yttrium oxide and rare earth oxides, such that ions of the rare earth oxide, ions of the yttrium oxide, ions of the combination of rare earth oxides, and ions of the combination of rare earth oxides and yttrium oxide have an average ionic radius of about 0.97, to achieve a particle size below 1.0 micron;
b. drying the wet milled compounds at about 150° C.; then,
c. granulating and mildly calcining the dried, wet milled compounds at about 500° C. to 600° C.; and,
d. then mixing the calcined, dried, wet milled compounds with at least ninety weight percent essentially pure barium titanate powder having an average particle size of from 0.2 to 1.2 microns.

### Claim 10 (depends on 9)

The method of manufacturing a dielectric ceramic start powder of claim 9, comprising the further step of wet milling between 0.01 to 0.4 weight percent silver with the compounds being wet milled.

### Claim 11 (depends on 1)

A method of making a multilayer ceramic capacitor that satisfies X7R capacitor performance characteristics, comprising the steps of:
a. preparing a mixture of the dielectric ceramic start powder of claim 1;
b. mildly calcining the dielectric ceramic start powder at about 450° C. to about 500° C. to obtain a dielectric start powder comprised of agglomerates of the mixture of start powders wherein each of the agglomerates has essentially the same compositional ratios as the start powder of the barium titanate, flux, Nb2O5, MnCO3, Co3O4, and the additive of rare earth oxide, yttrium oxide, combination of rare earth oxides, or combination of yttrium oxide and rare earth oxides;
c. forming a slurry of the calcined ceramic powder;
d. preparing layers of the slurry;
e. forming a stack of a plurality of the layers and interleaving at least one silver or silver-palladium electrode between adjacent layers; and
f. heating to mature the stack of layers by sintering in open air at a temperature of between 875° C. to 1,025° C. to produce a multilayer ceramic capacitor body with at least one buried electrode.

### Claim 12 (depends on 11)

The method of making the multilayer ceramic capacitor of claim 11, comprising the further step of mixing with the dielectric ceramic start powder 1.0 weight percent of the barium lithium borosilicate flux before the mildly calcining step.

### Claim 13 (depends on 11)

The method of making the multilayer ceramic capacitor of claim 11, comprising the further step of mixing with the dielectric ceramic start powder from 0.01 to 0.4 weight percent silver before the mildly calcining step.

### Claim 14 (depends on 11)

The method of making the multilayer ceramic capacitor of claim 11, wherein the silver-palladium electrode comprises 85 weight percent or more of silver.

### Claim 15

A multilayer ceramic capacitor that satisfies X7R performance characteristics having at least one electrode buried within a body of the capacitor, and an external terminal connected to at least one electrode, the body comprising:
a. at least ninety weight percent essentially pure barium titanate powder having an average particle size of from 0.2 to 1.2 microns;
b. from 0.2 to 2.5 weight percent of barium lithium borosilicate flux;
c. from 0.05 to 0.3 weight percent of MnCO3;
d. a grain growth inhibitor selected from the group consisting of niobium compounds Nb2O5, BaNb2O6, CaNb2O6, MgNb2O6, LiNbO3, and mixtures thereof such that a weight percent of Nb2O5 ranges from 0.4 wt % to 1.50 wt %, and tantalum compounds, and mixtures thereof, such that a weight percent of Ta2O5 ranges from 0.66 wt % to 2.50 wt %, and a mixture of molar equivalents of the niobium and tantalum compounds; and,
e. from 0.4 to 1.2 weight percent of an additive selected from the group consisting of a rare earth oxide, yttrium oxide, a combination of rare earth oxides, and a combination of yttrium oxide and rare earth oxides, such that ions of the rare earth oxide, ions of the yttrium oxide, ions of the combination of rare earth oxides, and ions of the combination of rare earth oxides and yttrium oxide have an average ionic radius of about 0.97 angstroms.

### Claim 16 (depends on 15)

The multilayer ceramic capacitor of claim 15, wherein the body further comprises about 1.0 weight percent of the barium lithium borosilicate flux.

### Claim 17 (depends on 15)

The multilayer ceramic capacitor of claim 15, wherein the body further comprises from 0.01 to 0.4 weight percent silver and from 0.01 to 0.25 weight percent Co3O4.

### Claim 18 (depends on 15)

The multilayer ceramic capacitor of claim 15, wherein oxides within the barium lithium borosilicate flux are in a mole percent range of BaO from 16.25 to 46.25 mole percent, Li2O from 20.1 to 46.9 mole percent, B2O3 from 8.75 to 28.75 mole percent, and SiO2 from 9.9 to 23.1 mole percent.

### Claim 19 (depends on 15)

The multilayer ceramic capacitor of claim 15, wherein the body further comprises from 0.01 to 0.4 weight percent copper.

### Claim 20 (depends on 15)

The multilayer ceramic capacitor of claim 15, wherein the body further comprises about 0.1 weight percent MnCO3 and about 0.1 weight percent Co3O4.