Uniaxial stress dependence of the permittivity of electroceramics

Abstract

The dependence of the permittivity on uniaxial pressure of ceramics in the paraelectric, ferroelectric and relaxor phases has been investigated for BaTiO 3, Pb(ZrTi)O 3 and Pb(Mg 1/3Nb 2/3)O 3. In the paraelectric phase, upon the application of stress, a reversible decrease in the permittivity is observed. In the ferroelectric phase, the observed behaviors can be divided in two classes depending on the type of ionic defects present in the ceramics. Both behaviors are characterized by an instantaneous increase in the permittivity at both stress application and release (Δσ) but they differ in the following relaxation which can be a decrease (type A) or an increase (type B) in the permittivity. In relaxor materials the behaviors observed are similar to the paraelectric and ferroelectric phases as the temperature is lowered. The mechanisms of the different observed behaviors are discussed.