Mra Laboratories, Inc.

Samir G Maher

Galeb H Maher

James M Wilson

A dielectric ceramic powder and multilayer ceramic capacitors made from the powders are disclosed. A dielectric start powder mixture includes 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; from 0.1 to 0.3 weight percent of MnCO ; 0.4 to 1.50 weight percent Nb  or a niobate compound, or a molar equivalent of Ta O or a tantalum compound as a grain growth inhibitor; and, 0.4 to 1.2 weight percent of gadolinium oxide (Gd O ). The start powder mixture is calcined and then sintered in an open zirconia setter at from 950&deg; C. to 1,025&deg; C. to produce a dielectric ceramic body that satisfies X7R capacitor performance characteristics; that includes no hazardous heavy metal oxides; and, that may include silver-palladium electrodes having 85 weight percent or more of silver.

High dielectric constant very low fired X7R ceramic capacitor, and powder for making

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 MnCO ; 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.

In a start powder mixture of magnesium zinc titanate and a barium lithium boro-silicate flux, it is discovered that the addition of lithium to the flux enables the manufacture of multilayer ceramic capacitors using the powder mixture, that perform to the COG standard including an accelerated life test. This addition of lithium also makes possible the sintering to maturity of COG multilayer capacitors at temperatures as low as 950&deg; C., which in turn allows the use of silver-palladium alloy buried electrodes of high silver and low palladium content which in turn lead to higher capacitor Q and lower manufacturing costs.

Magnesium zinc titanate powder with a barium boron lithium silicate flux and a multilayer ceramic COG capacitor made therefrom

Temperature compensating capacitors and dielectric ceramic powder compositions therefor are disclosed, based upon a dual-component barium borate and zinc silicate sintering flux. The precursor dielectric ceramic powders can include (1&minus;m) BaTiO,&plus;(m) CaZrO,(BTCZ composition), with m ranging from 20 mole percent to 35 mole percent, xBaO.yTiO,.zRE,O,(rare earth composition), (RE being a rare earth metal), with x ranging from 0 m % to 30 m %, y ranging from 45 m % to 95 m %, and z ranging from 5 m % to 50 m %, or a combination of the BTCZ and rare earth composition in varying weight percents. The effective range of B,O,in the barium borate ranges from 0.029 w % to 2.75 w % of the total dielectric composition, whereas the effective range of SiO,in the zinc silicate ranges from 0.08 w % to 1.42 w % of the total dielectric composition.

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Williamstown, MA, United States of America

Samir G Maher