Low thermal conductivity in A-site high entropy perovskite relaxor ferroelectric

Abstract

An A-site disordered high entropy perovskite (Pb1/6Ba1/6Sr1/6Ca1/6Na1/6Bi1/6)TiO3 (PBSCNBi) ceramic was prepared by a solid-state reaction method. XRD and scanning electron microscopy-energy dispersive x ray confirmed a single-phase tetragonal solid solution. Dielectric and hysteresis loop measurements showed relaxor ferroelectricity at room temperature; Curie Weiss fitting gives a Burns temperature (Tb) of 123 °C, and Vogel–Fulcher fitting gives a freezing temperature (Tf) of −67.24 °C, which confirms the room-temperature relaxor ferroelectricity of PBSCNBi. This is attributed to local chemical inhomogeneities in the high entropy ceramics. PBSCNBi also has a low thermal conductivity (1.15 W m−1 K−1 at room temperature) compared to all of its constituent simple perovskites (e.g., BaTiO3, PbTiO3, SrTiO3 CaTiO3, and Na1/2Bi1/2TiO3 in the range of 25–100 °C), which is attributed to the enhanced phonon scattering by both polar nanoregions and the mass contrast effect in the multi-element perovskite. This work demonstrates the great potential of making A-site high entropy ceramics with relaxor ferroelectric properties.