Grain Growth and Densification of Hot-Pressed Lead Zirconate-Lead Titanate Ceramics Containing Bismuth

Grain growth and densification were studied in a hot-pressed ferroelectric composition of 65/35 (Zr/Ti molar ratio) lead zirconate-lead titanate containing 2 at.% bismuth. The grain growth and densification rate processes were measurable from 1050° to 1300°C and from 700° to 1100°C, respectively. Grain growth as a function of time followed a ⅓ power law ( D (grain size) = kt ^⅓). An activation energy of 95 kcal/mole was calculated. Densification was a two-stage process as a function of time: a rapid initial stage and a slower final stage. The initial stage of densification behaved viscously with an activation energy of 36.7 kcal/mole. Grain boundary sliding and the Nabarro-Herring mechanism of stress-directed movement of vacancies are suggested as the densification mechanisms. Results indicated that densification is sensitive to stoichiometry and to additives.