Large piezoelectricity and dielectric permittivity in BaTiO₃-xBaSnO₃ system: The role of phase coexisting

Yonggang Yao¹, Chao Zhou¹, Duchao Lv¹, Dong Wang¹, Haijun Wu¹, Yaodong Yang^1a and Xiaobing Ren^1,2b

¹ Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, Xian Jiaotong University - Xi'an 710049, China
² Ferroic Physics Group, National Institute for Materials Science - Tsukuba 305-0047, Ibaraki, Japan

^a yaodongy@mail.xjtu.edu.cn
^b ren.xiaobing@mail.xjtu.edu.cn

Received: 17 February 2012
Accepted: 26 March 2012

Abstract

We report ultrahigh dielectric and piezoelectric properties in BaTiO₃-xBaSnO₃ ceramics at its quasi-quadruple point, a point where four phases (Cubic-Tetragonal-Orthorhombic- Rhombohedral) nearly coexist together in the temperature-composition phase diagram. At this point, dielectric permittivity reaches ∼75000, a 6–7-fold increase compared with that of pure BaTiO₃ at its Curie point; the piezoelectric coefficient d₃₃ reaches 697 pC/N, 5 times higher than that of pure BaTiO₃. Also, a quasi-quadruple point system exhibits double morphotropic phase boundaries, which can be used to reduce the temperature and composition sensitivity of its high piezoelectric properties. A Landau-Devonshire model shows that four-phase coexisting leading to minimizing energy barriers for both polarization rotation and extension might be the origin of giant dielectric and piezoelectric properties around this point.