Giant electrocaloric effect in BaTiO3–Bi(Mg1/2Ti1/2)O3 lead-free ferroelectric ceramics

Abstract

The microstructure, dielectric property and electrocaloric effect were investigated in the lead-free (1-x)BaTiO3–x (BiMg1/2Ti1/2)O3 ((1-x) BT–x BMT, x = 0.0–0.05) ferroelectric ceramics. Under the low electric field (E ≤ 20 kV cm−1), the coexistence of a positive and negative electrocaloric effect was obtained in (1-x)BT–x BMT (x ≤ 0.04) ceramics system using the Maxwell relation. Negative electrocaloric behavior disappears and the positive electrocaloric effect was only observed at high electric field (E ≥ 25 kV cm−1). Firstly, the values of both negative electrocaloric effect under low electric field of E ≤ 20 kV cm−1 (NECE) and positive electrocaloric effect in the high electric field of E ≥ 25 kV cm−1 (PECE) increase, then decrease with increasing BMT content in the ceramics. The 0.98BT-0.02BMT ceramic shows the excellent PECE and NECE capabilities. The corresponding giant electrocaloric effect values of −0.37 K (42 °C) at 20 kV cm−1 and 1.21 K (143 °C) at 55 kV cm−1 were observed. These results show great potential in achieving large cooling power as refrigerants.