Direct and indirect characterization of electrocaloric effect in (Na,K)NbO_3 based lead-free ceramics

摘要

This paper demonstrated the electrocaloric effect (ECE) of (Na_(0.52)K_(0.48-x))(Nb_(0.92-x)Sb_(0.08))O_3-xLiTaO_3 lead-free ceramics by direct differential scanning calorimetry measurement and indirect thermodynamic method. Both results show good consistency, where the direct one more accurately depicts ECE value and its evolution according to phase diagram. Due to the diffuse orthorhombic-tetragonal phase transition, the samples show a broad ECE peak which shifts to lower temperature with increasing LiTaO_3 amount. Compared to previous direct results in lead-free ceramics at corresponding temperatures, they show a competitive ECE performance with △T_(max) of 0.41 K (@80℃), 0.30K (@35℃) and 0.16K (@15℃) under 20kV/cm fields for x = 0.02, 0.0375 and 0.045.