US 4,832,939 AGranted

Barium titanate based dielectric compositions

AssigneeCabot Corporation

InventorsJameel Menashi, Robert C. Reid, Laurence P. Wagner

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Abstract

The present invention involves a method for producing a variety of barium titanate based powder products consisting of submicron, dispersible primary particles having narrow size distributions. The method, in its broadest aspects, involves heating an aqueous slurry of PbO, or Pb(OH).sub.2, and Ca(OH).sub.2 with a stoichiometric excess of the hydrous oxides of Ti(IV), Sn(IV), Zr(IV) and Hf(IV) to a temperature not exceeding 200.degree. C. Thereafter, the resulting slurry temperature is adjusted to between 50.degree. and 200.degree. C. and a solution of Ba(OH).sub.2 and Sr(OH).sub.2, having a temperature of 70.degree. to 100.degree. C. is added within a period of five minutes or less to the slurry. About 10 minutes after the addition of the Ba(OH).sub.2 and Sr(OH).sub.2 solution is completed, the slurry is heated to a temperature not exceeding 225.degree. C. to ensure formation of a stoichiometric perovskite product. Thereafter, the slurry is cooled and the solid product is recovered.

Claims10

Dependent claims

A method for producing submicron, dispersible perovskite based products having substantially the formula:

Ba.sub.(1-x-x'-x") Pb.sub.x Ca.sub.x' Sr.sub.x" Ti.sub.(1-y-y'-y") Sn.sub.y Zr.sub.y' Hf.sub.y" O.sub.3
where the mole fractions x, x', x", y, y', and y" each have independent values ranging from 0 to 0.3, and the sum of either (x+x'+x") or (y+y'+y") does not exceed 0.4, comprising:
(a) Heating an agitated aqueous slurry containing x moles of PbO or Pb(OH).sub.2, x' moles of CaO or Ca(OH).sub.2, (1-y-y'-y") moles of hydrous TiO.sub.2, y moles of hydrous SnO.sub.2, y' moles of hydrous ZrO.sub.2 and y" moles of hydrous HfO.sub.2 to a temperature in the range of from about 100.degree. to 200.degree. C.,
(b) Adjusting the temperature of the aqueous agitated slurry to a temperature in the range between 50.degree. and 200.degree. C.,
(c) Adding to the agitated slurry of solution, having a temperature between 70.degree. and 110.degree. C., containing x" moles of Sr(OH).sub.2 and up to a 20% excess of the stoichiometric requirement, (1-x-x'-x"), of Ba(OH).sub.2 over a period from about 0.1 to about 5 minutes,
(d) Holding the agitated slurry at the temperature used in step (b) for a period of 10 to 30 minutes,
(e) Heating the agitated slurry to a temperature not exceeding 225.degree. C. to ensure formation of a stoichiometric perovskite product,
(f) Cooling the slurry and separating the perovskite product.

5 more elements

Dependencies are inferred from the claim text.