Phase transition temperatures and electrical properties of divalent ions (Ca2+, Sr2+ and Ba2+) substituted (Bi1/2Na1/2)TiO3 ceramics

Phase transition temperature and electrical properties of divalent ions (Ca2+, Sr2+ and Ba2+) substituted (Bi1/2Na1/2)TiO3 (BNT)-based ceramics were studied to investigate the relationship between the substituted ion and the effect on various characteristics. These ceramics were prepared by a conventional ceramic fabrication process. The behavior of the depolarization temperature, Td, slope depends on the substituted ionic radius before correspondence of the Td to the rhombohedral–tetragonal phase transition temperature, TR–T (0–3 at% for Ba2+-substituted BNT). The piezoelectric constant, d33, of Ca2+ and Sr2+ increased because of the increase of their free permittivity, ε33T/ε0, accompanying a decrease of Td. On the other hand, the d33 of Ba2+-substituted BNT increased with increasing amount of Ba2+ below 7 at% because Ba2+-substituted BNT has a MPB composition. Therefore, the d33 of Ba2+ 7 at% substituted BNT had a maximum of 152 pC/N. Td has a trade-off relationship with d33.