Negative electrocaloric effect in antiferroelectric PbZrO₃

¹ Jožef Stefan Institute - Jamova 39, 1001 Ljubljana, Slovenia
² Jožef Stefan Postgraduate School - Jamova 39, 1000 Ljubljana, Slovenia

Received: 13 May 2014
Accepted: 11 June 2014

Abstract

The dielectric and thermal properties of a typical antiferroelectric (AFE) material are investigated by minimising numerically the free energy as given by the Kittel model of AFEs. The phase line of second-order phase transitions in the phase diagram is shown to change to a first-order line at the tricritical point T_3cp, E_3cp. The static dielectric susceptibility and the electrocaloric (EC) effect are calculated as a function of temperature and the applied electric field E. It is found that in a given range of electric fields and temperatures the EC effect has negative values but generally becomes positive above the AFE ordering temperature T₀. The dielectric susceptibility shows characteristic peaks at the phase transitions between the field-induced polar and the AFE antipolar phase, and diverges at the tricritical point. We present experimental results for a negative EC effect, which have been obtained by direct EC measurements in PbZrO₃ ceramics, and agree qualitatively with the above model.