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

Ba(HfxTi1–x)O3 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 TC of Ba(HfxTi1–x)O3 ceramics decreased, while TT–O and TO–R increased with the increase of hafnium content. Large electrocaloric effect values of 1.64 K (117 °C) and 1.21 K (76 °C) were observed for Ba(HfxTi1–x)O3 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 (ΔTf /ΔE ≥ 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 ΔTf /ΔE = 0.38 K·mm·kV–1 was achieved in a smaller electric field for Ba (HfxTi1–x)O3 with x = 0.03 compositions.