Method for making a BaTiO3 powder mixture the powder mixture and method for making a Y5V ceramic body therefrom

Claim 1

A method for making a ceramic powder mixture comprising: a) preparing a powder mixture having an average particle size of about 1 micron by combining: from 96 to 98 mole percent of precursors of a stoichiometric barium zirconate titanate (BZT) wherein zirconium amounts to from 13.5 to 15.0 mole percent, and wherein up to 4 mole % of said barium is replaced by strohtium; a compound containing from 0.5 to 1.5 mole percent of Curie-point shifter cations; a sintering flux consisting of from 1.2 to 2.6 weight percent of a cadmium silicate wherein the molar ratio of CdO to SiO 2 ranges from 1:1 to 3:1 inclusive; from zero to 0.01 mole percent of Pb; and from zero to 2 mole % of an alkaline earth metal selected from barium, calcium, strontium and combinations thereof to effect in said powder mixture a ratio (A/B) of the large cations (A) to the small cations (B) in the range from 1.024 to 1.035; and b) partially calcining said homogeneous mixture at approximately 700° C. to obtain a powder comprised of agglomerates of said homogeneous powder mixture wherein each of said agglomerates has essentially the same composition, to provide a powder mixture capable of being formed into a body that can be fired to maturity at no higher than 1100° C., and subsequently annealed at a lower temperature to provide a mature dielectric ceramic body meeting the Y5V standard and having a dielectric constant greater than 10,000 at the Curie temperature which lies between 0°-20° C.

Claim 2

A method for making a ceramic powder mixture comprising: a) preparing a powder mixture having an average particle size of about 1 micron by combining: from 96 to 98 mole percent of precursors of a stoichiometric barium zirconate titanate (BZT) wherein zirconium amounts to from 13.5 to 15.0 mole percent, and wherein up to 4 mole % of said barium is replaced by strohtium; a compound containing from 0.5 to 1.5 mole percent of Curie-point shifter cations; a sintering flux consisting of from 1.2 to 2.6 weight percent of a cadmium silicate wherein the molar ratio of CdO to SiO 2 ranges from 1:1 to 3:1 inclusive; from zero to 0.01 mole percent of Pb; and from zero to 2 mole % of an alkaline earth metal selected from barium, calcium, strontium and combinations thereof to effect in said powder mixture a ratio (A/B) of the large cations (A) to the small cations (B) in the range from 1.024 to 1.035; and b) partially calcining said homogeneous mixture at approximately 700° C. to obtain a powder comprised of agglomerates of said homogeneous powder mixture wherein each of said agglomerates has essentially the same composition, to provide a powder mixture capable of being formed into a body that can be fired to maturity at no higher than 1100° C., and subsequently annealed at a lower temperature to provide a mature dielectric ceramic body meeting the Y5V standard and having a dielectric constant greater than 10,000 at the Curie temperature which lies between 0°-20° C.

Claim 6

A method for making a dielectric ceramic body comprising: a) preparing a powder mixture having an average particle size of about 1 micron by combining: from 95 to 98 weight percent of precursors of a stoichiometric barium zirconate titanate (BZT) wherein zirconium amounts to from 13.5 to 15.0 mole percent of all the small cations in said BZT, and wherein up to 4 mole percent of said barium is replaced by strontium; from 0.5 to 1.5 mole percent of a Curie-point shifter cations, from a sintering flux consisting of 1.2 to 2.6 weight percent of a cadmium silicate wherein the molar ratio of CdO to SiO 2 ranges from 1:1 to 3:1 inclusive, from zero to 0.01 mole percent of Pb, from zero to 2 mole percent of an alkaline earth metal selected from barium, calcium, strontium and combinations thereof to effect in said powder mixture a ratio (A/B) of the large cations (A) to the small cations (B) in the range from 1.024 to 1.035, wherein the alkaline-earth metals, lanthanum and cadmium are large cations; and titanium, zirconium, niobium and manganese are small cations; b) further mixing said powder mixture to form a homogenous powder mixture; and c) partially calcining said homogeneous mixture at approximately 700° C. to obtain a powder comprised of agglomerates of said homogeneous powder mixture; d) forming a body of said calcined homogeneous mixture; e) applying at least two separate electrodes to said body f) sintering said body at about 1100° C. in a closed container; and g) annealing said body at about 1050° C. in an open air atmosphere to provide a mature dielectric ceramic body having a dielectric constant greater than 10,000 at the Curie temperature which lies between 0°-20° C.

Claim 7

A method for making a dielectric ceramic body comprising: a) preparing a powder mixture having an average particle size of about 1 micron by combining: from 95 to 98 weight percent of precursors of a stoichiometric barium zirconate titanate (BZT) wherein zirconium amounts to from 13.5 to 15.0 mole percent of all the small cations in said BZT, and wherein up to 4 mole percent of said barium is replaced by strontium; from 0.5 to 1.5 mole percent of a Curie-point shifter cations, from a sintering flux consisting of 1.2 to 2.6 weight percent of a cadmium silicate wherein the molar ratio of CdO to SiO 2 ranges from 1:1 to 3:1 inclusive, from zero to 0.01 mole percent of Pb, from zero to 2 mole percent of an alkaline earth metal selected from barium, calcium, strontium and combinations thereof to effect in said powder mixture a ratio (A/B) of the large cations (A) to the small cations (B) in the range from 1.024 to 1.035, wherein the alkaline-earth metals, lanthanum and cadmium are large cations; and titanium, zirconium, niobium and manganese are small cations; b) further mixing said powder mixture to form a homogenous powder mixture; and c) partially calcining said homogeneous mixture at approximately 700° C. to obtain a powder comprised of agglomerates of said homogeneous powder mixture; d) forming a body of said calcined homogeneous mixture; e) applying at least two separate electrodes to said body f) sintering said body at about 1100° C. in a closed container; and g) annealing said body at about 1050° C. in an open air atmosphere to provide a mature dielectric ceramic body having a dielectric constant greater than 10,000 at the Curie temperature which lies between 0°-20° C.