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BaTiO3 based ferroelectric materials for electrocaloric cooling applications
The aim of this project was to produce electrocaloric materials and to determine the potential of these materials for electrocaloric cooling applications. The electrocaloric effect (ECE) of lead-free Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.10) ferroelectric ceramics was studied. The phase analysis of each ceramic composition that was synthesized by conventional solid-state reaction technique was performed by X-ray Diffraction. Dielectric measurements were done to determine the phase transition temperatures (Curie temperature, Tc) of all compositions and also construct a phase diagram. ΔT values were calculated indirectly using electrical polarization curves measured at different temperatures and Maxwell's equations. ΔT values that were obtained from different regions of the phase diagram are compared. The most suitable composition for applications was chosen considering the ΔT value, temperature range where relatively large ΔT is preserved and the Curie temperature of all ceramics. Ba0.8Sr0.2Ti0.93Zr0.07O3 ceramic located near the critical point shows the best performance with ΔT value of 0.40 K under 20 kV/cm. In comparison with the lead-free ceramics studied in the literature, Ba0.8Sr0.2Ti1-xZrxO3 system can be considered as one of the best candidates for future electrocaloric cooling technologies.