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.

Dielectric Properties of BaZr0.2[Ti(1-x)Mgx/3Ta2x/3]0.8O3 Solid Solution

“…BaTiO 3 based ferroelectric materials have received a great deal of attention from scientific community as an alternative for lead free materials for extensive applications in capacitors, piezoelectric devices and transducers (Wang et al, 2012;Chen et al, 2014;Magnone et al, 2016;Li et al, 2017;Co et al, 2020;Venkatachalam et al, 2020). The high curie temperature (128°C) and intrinsically low relative permittivity in pure BaTiO 3 make it unsuitable in practical device applications (Hennigs and Schnell, 1982).…”

Electrocaloric Effect in Different Oriented BaZr0.15Ti0.85O3 Single Crystals

“…In recent years, lead-free barium zirconate titanate (BaZr x Ti 1–x O 3 ) has attracted much attention due to its rich phase structure and excellent electrocaloric (EC) properties [ 19 , 20 , 21 , 22 , 23 , 24 ]. Direct measurement by Qian et al indicates that when the change of the electric field is 2.1 MV/m, BaZr 0.2 Ti 0.8 O 3 ceramics at 38 °C exhibit an EC temperature change of 1.1 °C with a large EC coefficient of around 0.5 × 10 −6 KmV −1 [ 19 ].…”

Machine-Learning-Enabled Prediction of Adiabatic Temperature Change in Lead-Free BaTiO3-Based Electrocaloric Ceramics

“…Therefore, they cannot be used in a high-throughput manner to model solid solutions of arbitrary compositions. In addition to effective Hamiltonian methods, Landau theory-based thermodynamic models are used to model the EC effect in ferroelectric materials. , According to the Landau phenomenological approach, the Δ T in ferroelectrics can be calculated using the formula where is the temperature-dependent coefficient of the second-order term in the Landau free energy of the dipolar system and T 0 is the instability temperature, C latt is the lattice heat capacity, P ( E , T ) is the polarization as a function of electric field ( E ) and temperature ( T ), and the last term vanishes for T greater than the T C , because P 0 ( T ) = 0 when T ≫ T C . According to eq , to achieve large Δ T we need small C latt and large P ( E , T ) over a broad electric field and temperature range.…”