Barium titanate based dielectric compositions

US4832939A · kind A · utility

Assignee

• Cabot Corporation · US

Inventors

• Jameel Menashi · Lexington, US
• Robert C. Reid · Calle de la Era, AU
• Laurence Wagner · San Jose, US

Key dates

• Filing date: Feb 1, 1988
• Grant date: May 23, 1989
• Expiry date: Feb 1, 2008

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S502/525
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

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.