Electrocaloric and pyroelectric properties of barium zirconate titanate

Abstract

The electrocaloric response of bulk monodomain BaZrxTi(1−x)O3 (BZT) under modest electrical fields at room temperature has been evaluated using a Landau theory thermodynamic model as a function of the zirconium content x. The computations show that increasing x changes the nature of the ferroelectric phase transitions of BZT. There are potentially three ferroelectric phases in BZT for zirconium contents 0 < x < 0.30. For 0 < x < 0.15, the cubic paraelectric phase transitions successively into the tetragonal, orthorhombic, and rhombohedral phases with decreasing temperature. For x > 0.15, the rhombohedral phase becomes the sole ferroelectric phase upon cooling from the cubic paraelectric state. The magnitude of the polarization discontinuity at the phase transition decreases with increasing x as it approaches a continuous, second order transition. We show here that these phase changes have a significant effect on electrocaloric and pyroelectric properties of BZT. The room temperature adiabatic temperature change was calculated for compositions of BZT with 0 < x < 0.30, revealing a maximum temperature change of ΔTad = 1.25 °C for an electric field difference of 100 kV/cm for x = 0.20 near room temperature.