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, T-d, slope depends on the substituted ionic radius before correspondence of the T-d to the rhombohedral-tetragonal phase transition temperature, TR-T (0-3 at% for Ba2+-substituted BNT). The piezoelectric constant, d(33), of Ca2+ and Sr2+ increased because of the increase of their free permittivity, epsilon(T)(33)/epsilon(0), accompanying a decrease of T-d. On the other hand, the d(33) of Ba2+-substituted BNT increased with increasing amount of Ba2+ below 7 at% because Ba2+-substituted BNT has a MPB composition. Therefore, the d(33) of Ba2+ 7 at% substituted BNT had a maximum of 152 pC/N. T-d has a trade-off relationship with d(33). (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.