Crystal growth of SmxY1−xCa4O(BO3)3 for piezoelectric applications at high temperature

Abstract

Various 2 inch Sm_xY_1−xCa₄O(BO₃)₃ (Sm_xY_1−xCOB) crystals with good quality were grown successfully along the <010> axis by the Czochralski method. As the amount added increased, the unit cell dimensions for the obtained crystals were found to increase. At room temperature, the relative dielectric constants ε^E₁₁/ε₀, ε^E₂₂/ε₀ and ε^E₃₃/ε₀ were found to be 9.57, 11.87 and 9.58 for Sm_0.05Y_0.95COB, 9.66, 12.33 and 9.64 for Sm_0.3Y_0.7COB, 9.70, 12.78 and 9.75 for Sm_0.5Y_0.5COB, and 9.73, 14.10 and 10.14 for Sm_0.75Y_0.25COB, respectively. The electromechanical coupling factors and piezoelectric coefficients as a function of Sm content were studied, with maximum values found in the Sm_0.75Y_0.25COB crystal. All the as-grown crystals were observed to possess ultrahigh resistivities, and the values of the electrical resistivities of Sm_xY_1−xCOB were approximately 1.1–3.1 × 10⁸ Ω cm at 850 °C. In the range of the test temperature, the dielectric losses for the Sm_xY_1−xCOB crystals were determined to be less than 45% at 840 °C, which together with the high thermal stability of the electromechanical and piezoelectric properties, with a variation of less than 5.5% at 850 °C, make the Sm_xY_1−xCOB crystals important candidate materials for high-temperature piezoelectric applications.