The effect of low Sn doping on the dielectric and electrocaloric properties of ferroelectric ceramics Ba0.95Sr0.05Ti0.95Zr0.05O3

Ba0,95Sr0,05(Ti0,95Zr0,05)1-xSnxO3 (x = 0 and x = 0.025) ceramics were prepared by solid state method. We have systematically studied the effects of a low quantity of Sn substitution on the crystal structure, dielectric and electrocaloric properties. X-ray diffraction shows that the symmetry of the two compositions x = 0 (BSTZ) and x = 0.025 (BSTZS) is both tetragonal with a space group P4mm and orthorhombic with Pmmm space group. Dielectric measurements show that Sn doping significantly reduces the Curie temperature from 392 K for BSTZ to 364 K for BSTZS. A typical hysteresis loops were observed for the investigated compositions and they were confirmed the ferroelectric-to-paraelectric transition phase. Finally electrocaloric effect in lead-free BSTZ and BSTZS ceramics is studied using an indirect method from the thermal variation of P-E hysteresis loops using the Maxwell relation. In the composition x = 0, the electrocaloric temperature ΔT was about 0.048 K. The addition of a low quantity of tin (Sn) ions in the matrix of Ba0,95Sr0,05(Ti0,95Zr0,05) has been able to increase the electrocaloric temperature until ΔT reached 0.095 K to a field E = 1 kV/mm.