Enhanced Electrocaloric Effect in Sr2+-Modified Lead-Free BaZr xTi1- xO3 Ceramics
Xiao-Dong Jian1,2, Biao Lu1, Dan-Dan Li1
1Guangdong Provincial Research Center on Smart Materials and Energy Conversion Devices, Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, School of Materials and Energy , Guangdong University of Technology , Guangzhou 510006 , China.
Abstract:
Barium strontium zirconate titanate ceramics ((BaSr)(ZrTi)O3-BSZT) with Zr4+ ionic contents of 15 and 20 mol % and Sr2+ ionic contents of 15, 20, 25, and 30 mol % were prepared using a solid-state reaction approach. X-ray diffraction and scanning electron microscopy were used to characterize the lattice structure and morphologies of the ceramics. Permittivity and polarization as a function of temperature were characterized using an impedance analyzer and a Tower-Sawyer circuit. The electrocaloric effect was measured directly and calculated using the Maxwell relation (indirectly). The results indicated that the BSZT ceramics change from a normal ferroelectric to a relaxor ferroelectric with increasing Zr4+ ionic content, which can be further modified by the addition of Sr2+ ionic content. The optimized adiabatic temperature change Δ T obtained is 2.43 K in (Ba0.85Sr0.15)(Zr0.15Ti0.75)O3 ceramics, and Δ T >1.6 K over a wide temperature span of 120 °C was obtained.
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