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

Ba(Hf x Ti 1– 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(Hf x Ti 1– x )O 3 ceramics decreased, while T T–O and T O–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(Hf x Ti 1– 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 ( Δ T f / Δ 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 Δ T f / Δ E = 0.38 K·mm·kV –1 was achieved in a smaller electric field for Ba (Hf x Ti 1– x )O 3 with x = 0.03 compositions.