Role of potassium content in sodium bismuth titanate piezoelectrics for higher temperature applications.

Potassium sodium bismuth titanate (KNBT) ceramics have useful dielectric and piezoelectric properties, and are candidates for higher temperature (>200_C) applications than possible with PZT. A diffuse transformation to the cubic state occurs above 500_C. At lower temperatures, relaxor-type behavior is observed around 200_C. We report ferroelectric and piezoelectric properties for poled ceramics as a function of temperature, from room temperature through the relaxor transition, into the higher-temperature anti- ferroelectric region. Topics to be covered, include, mixed contributions to the overall field-induced strain at high temperatures in the AF region, i.e., from field-induced piezoelectricity and electrostriction; and how the lower-temperature region can be extended K substitution, for higher-temperature applications