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Homogenous Sn-doped K(Ta,Nb)O3 single crystals and its high piezoelectric response
Journal of Materiomics  (IF6.425),  Pub Date : 2021-11-13, DOI: 10.1016/j.jmat.2021.11.001
Fengying Liu, Yuanyuan Zhang, Limei Zheng, Gang Tian, Juan Du, Le Zhao, Xudong Chen, Xuping Wang, Minglei Zhao

Perovskite K(Ta,Nb)O3 (KTN) single crystal has drawn great interests for its outstanding electro-optic performance and excellent piezoelectric response. However, growth of compositionally uniform KTN single crystals has always been a great challenge for the great segregation difference between Nb and Ta. In this work, we propose a thermal field optimization strategy to resolve this challenge. Homogenous Sn doped KTN (Sn:KTN) single crystal with significantly reduced composition gradient (0.003 mol/mm, 1/4∼1/8 of other KTN system), minimal TC variation (13oC) and excellent piezoelectric and dielectric response (d33 =373 pC/N and ${\epsilon }_{33}^{T}$= 5206) has been successfully achieved. We found that the functional properties of Sn:KTN were greatly affected by the near-room temperature tetragonal-cubic phase transition. From the intrinsic aspect, longitudinal lattice deformation becomes much easier, resulting in maximum piezoelectric (${d}_{33}^{\ast }$), dielectric (${\epsilon }_{33}^{T\ast }$), elastic (${s}_{33}^{E\ast }$)and electromechanical coupling (${k}_{33}^{\ast }$) coefficients along polar direction [001]C. From the extrinsic aspect, both domain wall density and domain wall mobility are greatly improved for the reduced lattice distortion, which also contribute a lot to the functional properties. This work provides a simple and practical route for designing and growing high quality crystals, and more importantly, reveals the fundamental mechanism of the phase transitions/boundaries on the functional properties.