Characterization of the Dielectric, Piezoelectric, and Elastic Coefficients of Ca 3 TaGa 3 Si 2 O 14 Single Crystals up to 800 °C

In this paper, the dielectric, piezoelectric, and elastic properties of the Ca 3 TaGa 3 Si 2 O 14 (CTGS) single crystals were fully investigated over the temperature range of $\hbox{21}^{\circ}\text{C}{-}\hbox{800}\,^{\circ}\text{C}$ . Both the real and the complex coefficients were completely characterized. The real coefficients were determined through the measurements of the capacitance, impedance, or admittance of three kinds of plate samples ( X -cut, Y -cut, and Z -cut) and four types of bar samples [ XY -cut, $({ XYt})\hbox{45}^\circ$ , $({ XYt})-\hbox{30}^\circ$ , and $({ XYt})-\hbox{85}^\circ$ ], according to the IEEE dynamic methods. Of utmost importance are the complex coefficients, which were obtained by taking into account the electrical and mechanical dissipations of the specimens, and therefore, they could describe the materials’ performance more accurately. In light of the characterization method developed by Du et al. , three kinds of plate samples ( X -cut, Y -cut, and Z -cut) and two types of bar samples [ XY -cut and $({ XYt})-\hbox{85}^\circ$ ] were designed for the determination of the materials’ complex coefficients. Moreover, the temperature behaviors of all the independent dielectric, piezoelectric, and elastic coefficients (2, 2, and 6, respectively) were summarized: the real parts of the complex dielectric coefficients (equal to the real dielectric coefficients) rise gradually with the increase of the temperature, while the imaginary parts increase dramatically after $\hbox{400}^\circ{\rm C}$ ; both the real and complex piezoelectric coefficients stay relatively stable over the measurement temperature range; all the absolute values of the elastic compliance coefficients, to varying degrees, increase with the temperature, while the elastic stiffness coefficients decrease, and some of them exhibit excellent linearity.