Volume 115, Number 3, August 2016
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||26 August 2016|
Phase transition behaviours near the triple point for Pb-free (1 − x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics
1 State Key Laboratory of Electrical Insulation and Power Equipment and Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, Xi'an Jiaotong University - Xi'an, 710049, China
2 Center of Microstructure Science, Frontier Institute of Science and Technology, Xi'an Jiaotong University Xi'an, 710049, China
3 State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University - Xi'an, 710049, China
4 MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an Jiaotong University Xi'an 710049, China
5 Ferroic Physics Group, National Institute for Materials Science - Tsukuba, 305-0047, Ibaraki, Japan
Received: 1 August 2016
Accepted: 8 August 2016
The reason for the large electromechanical response in Pb-free piezoceramic Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) still remains controversial, and a central issue is whether or not the multi-phase-coexisting point (triple point) in the phase diagram is a thermodynamic tricritical point. In this letter, we study the phase transition behaviour for the ferro-para transitions of BZT-BCT specimens in the vicinity of a triple point. Our results show that latent heat and thermal hysteresis approach zero, while the permittivity peak value is maximized close to the triple-point composition, which suggests that the triple point exhibits nearly tricritical transition behaviours in the BZT-BCT system. Further, the TEM result shows that the domain width is minimized with composition approaching the triple point, which indicates a reduction of the domain wall energy possibly relevant to the tricriticality of the triple point. A sixth-order Landau energy modeling shows that the triple tricritical point provides a free-energy state of near-vanishing polarization anisotropy and thus enhances the piezoelectric response for such a material system.
PACS: 77.80.Dj – Domain structure; hysteresis / 77.80.B- – Phase transitions and Curie point / 77.84.Cg – PZT ceramics and other titanates
© EPLA, 2016
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