# US 11,897,815 B2 · Mg—Ta based dielectric ceramic for multi-layer ceramic capacitor and low-temperature preparation method thereof

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- Number: US 11,897,815 B2
- Document ID: US11897815B2
- Status: Granted
- Kind: B2
- Application number: 18/140,342
- Filed: 2023-04-27
- Published: 2023-11-02
- Granted: 2024-02-13
- Earliest claimed: 2022-04-29
- Assignees: Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China
- Applicants: Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China
- Inventors: YuanYuan Yang; XiaoZhen Li; MengJiang Xing; YanLing Luo; HongYu Yang; QingYang Fan
- Web page: https://patentgrep.com/patent/US11897815B2

## CPC

- C04B 35/495: based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates
- C04B 35/62685: {characterised by the order of addition of constituents or additives}
- C04B 35/6262: {of calcined, sintered clinker or ceramics}
- C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F})
- C04B 35/653: Processes involving a melting step
- H01G 4/1227: {based on alkaline earth titanates}
- H01G 4/1254: {based on niobium or tungsteen, tantalum oxides or niobates, tantalates}
- H01G 4/30: Stacked capacitors (H01G4/33 takes precedence)
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3215: Barium oxides or oxide-forming salts thereof
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3255: Niobates or tantalates, e.g. silver niobate
- C04B 2235/3262: Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
- C04B 2235/3281: Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
- C04B 2235/3409: Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
- C04B 2235/3418: Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
- C04B 2235/36: Glass starting materials for making ceramics, e.g. silica glass
- C04B 2235/442: Carbonates
- C04B 2235/6562: Heating rate
- C04B 2235/6567: Treatment time
- C04B 2235/76: Crystal structural characteristics, e.g. symmetry
- Y02E 60/13: Energy storage using capacitors
- 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)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A Mg—Ta based dielectric ceramic for multi-layer ceramic capacitor (MLCC) and a low-temperature preparation method thereof are provided. By providing a glass additive with high matching with a Mg—Ta ceramic, a modifier A+12CO3—B2+O—C3+2O3—SiO2 (A=Li, K; B=MnO, CuO, BaO; C=B, Al) is intruded in to a main material MgO—Ta2O5, which can significantly reduce the sintering temperature and provide a negative temperature coefficient of dielectric constant of −100±30 ppm/° C., and reduce the deterioration factors of loss caused by an additive for sintering, and prepare a dielectric material applied to RF MLCC with low loss, low cost and good process stability.

## Claims

### Claim 1

A magnesium-tantalum (Mg—Ta) based dielectric ceramic for multi-layer ceramic capacitor, comprising a ceramic material and a modifier;
wherein a chemical formula of the ceramic material is MgTa2O6;
a formula of the modifier is A2CO3—BO—C2O3—SiO2 with a mass ratio of 31:17:36:16, A2CO3 consists of 20 wt. % of Li2CO3 and 11 wt. % of K2CO3; BO consists of 2 wt. % BaO, 5 wt. % of MnO and 10 wt. % of CuO; and C2O3 consists of 30 wt. % of B2O3 and 6 wt. % of Al2O3;
a formula of the Mg—Ta based dielectric ceramic is MgTa2O6+2 wt. % of the modifier, the Mg—Ta based dielectric ceramic is prepared by a solid-state method, a main crystal phase of the Mg—Ta based dielectric ceramic is MgTa2O6 phase with a Trirutile structure; under a sintering temperature of 1150 degrees Celsius (° C.), a dielectric constant of the Mg—Ta based dielectric ceramic is 26.87, a dielectric loss of the Mg—Ta based dielectric ceramic is 1.71×10−4, and a value of a quality factor Q×f of the Mg—Ta based dielectric ceramic is 44398 GHz; and a temperature coefficient τε of the dielectric constant is stable and meets M2G temperature characteristics of (−55° C.: τε=−118 parts per million (ppm)/° C.; 85° C.: τε=−110 ppm/° C.);
the Mg—Ta based dielectric ceramic for multi-layer ceramic capacitor is prepared through the following steps:
step 1, mixing raw powders of magnesium oxide (MgO) and Ta2O5 according to the chemical formula MgTa2O6 to obtain a mixed powder;
step 2, putting the mixed powder prepared in step 1 into a ball milling tank, using zirconium balls and deionized water as a grinding medium and performing planet ball milling for 4-6 hours according to a mass ratio of the mixed powder:the zirconium balls:the deionized water of 1:4-5:2-4 to obtain a mixed slurry, drying the mixed slurry in an oven after the planet ball milling and then sieving with a 60-100 mesh sieve to obtain a sieved powder; and sintering the sieved powder in an atmosphere of 900-1000° C. for 3-5 hours to obtain MgTa2O6;
step 3, mixing raw powders of Li2CO3, K2CO3, BaO, MnO, CuO, B2O3, Al2O3, and SiO2 according a mass ratio of Li2CO3:K2CO3:BaO:MnO:CuO:B2O3:Al2O3:SiO2 of 20:11:2:5:10:30:6:16 to obtain a second mixed powder; using the zirconium balls and alcohol as a grinding medium and performing planet ball milling for 6-8 hours according to a mass ratio of the second mixed powder:the zirconium balls:the alcohol of 1:4-5:4-6 to obtain a ball-milled material, sintering the ball-milled material at a temperature of 600-650° C. for 3-6 hours after drying the ball-milled material and then heating to a temperature of 1450-1550° C. for melting for 3-5 hours to obtain a melted material, pouring the melted material into the deionized water for cooling to obtain a cooled material, and grinding the cooled material to a uniform power as the modifier;
step 4, mixing the modifier prepared in step 3 into MgTa2O6 prepared in step 2 according to the formula of the Mg—Ta based dielectric ceramic MgTa2O6+2 wt. % to obtain a third mixed power, performing planetary ball milling for 3-5 hours according to a mass ratio of the third mixed powder:the zirconium balls:the deionized water of 1:4-5:3-5 to obtain a second ball-milled material, and adding a polyvinyl alcohol solution, as a binder, into the second ball-milled material after drying the second ball-milled material to perform granulation to obtain a granular material; and
step 5: performing press-molding on the granular material prepared in step 4, heating at a heating rate of 2-5° C./minutes (min) and discharging glue at 600-650° C. for 3-5 hours, and then heating at the same heating rate to a temperature of 1150° C. and keeping the temperature for 4-6 hours, thereby obtaining a modified MgTa2O6 dielectric ceramic material.