Uniaxial stress dependence of the permittivity of electroceramics

The dependence of the permittivity, on uniaxial pressure of ceramics in the paraelectric, ferroelectric and relaxer phases has been investigated for B aTiO3, Pb(ZrTi)O-3 and Pb(Mg1/3Nb2/3)O-3. In the paraelectric ic phase, upo n the application of stress, a reversible decrease in the permittivity is o bserved. In the ferroelectric phase, the observed behaviors can be divided in two classes depending on the type of ionic defects present in the cerami cs. Both behaviors are characterized by an instantaneous increase in the pe rmittivity at both stress application and release (Delta sigma) but they di ffer in the following relaxation which can be a decrease (type A) or an inc rease (type B) in the permittivity. In relaxer materials the behaviors obse rved are similar to the paraelectric and ferroelectric phases as the temper ature is lowered. The mechanisms of the different observed behaviors are di scussed. (C) 1999 Published by Elsevier Science Limited. All rights reserve d.