Large Electrocaloric Effect in Lead-free Ba(HfxTi1-x)O3 Ferroelectric Ceramics for Clean Energy Applications

Ba(HfxTi1-x)O-3 ferroelectric ceramics were prepared by a conventional solid-state reaction process, and the correlation of structure, dielectric, ferroelectric, and electrocaloric properties were studied. The consequences indicated that the T-C of Ba(HfxTi1-x)O-3 ceramics decreased, while TT-O and TO-R increased with the increase of hafnium content. Large electrocaloric effect values of 1.64 K (117 degrees C) and 1.21 K (76 degrees C) were observed for Ba(HfxTi1-x)O-3 with x = 0.05 compositions. And, corresponding electrocaloric coefficients respectively were 0.33 and 0.24 K.mm.kV(-1). In addition, compared with the second-order phase transition region, larger electrocaloric coefficients (Delta T-f /Delta E >= 0.19 K. mm.kV(-1)) were obtained in the first-order phase transition region for all compositions. Meanwhile, the maximum values of electrocaloric coefficients Delta T-f /Delta E = 0.38 K.mm.V-1 was achieved in a smaller electric field for Ba(HfxTi1-x)O-3 with x = 0.03 compositions.