Electro-caloric effect in lead-free Sn doped BaTiO_3 ceramics at room temperature and low applied fields

摘要

Structural, dielectric, ferroelectric (FE), ~(119)Sn Moessbauer, and specific heat measurements of polycrystalline BaTi_(1-x)Sn_xO_3 (x = 0% to 15%) ceramics are reported. Phase purity and homogeneous phase formation with Sn doping is confirmed from x-ray diffraction and ~(119)Sn Mossbauer measurements. With Sn doping, the microstructure is found to change significantly. Better ferroelectric properties at room temperature, i.e., increased remnant polarization (38% more) and very low field switchability (225% less) are observed for x = 5% sample as compared to other samples and the results are explained in terms of grain size effects. With Sn doping, merging of all the phase transitions into a single one is observed for x≥ 10% and for x = 5%, the tetragonal to orthorhombic transition temperature is found close to room temperature. As a consequence better electro-caloric effects are observed for x = 5% sample and therefore is expected to satisfy the requirements for non-toxic, low energy (field) and room temperature based applications.