High-temperature piezoelectric single crystal ReCa4O(BO3)3 for sensor applications

Large-size and high-quality ReCa₄O(BO₃)₃ (ReCOB, Re = rare earth) single crystals were grown by the Czochralski pulling method. In this work, the electrical properties were investigated at room temperature and elevated temperature for YCa₄O(BO₃)₃ (YCOB). The dielectric permittivity, piezoelectric strain coefficient, and electromechanical coupling were found to be on the order of 11, 6.5 pC/N, and 12.5%, respectively, with a high piezoelectric voltage coefficient around 0.067 Vm/N. The electrical resistivity of YCOB was found to be 2 times 10⁸ Ohmmiddotcm at 800degC, with Q values of > 4,500 at 950degC. The frequency/temperature coefficient of YCOB was found to be -75 to -85ppm/K in the temperature range of 30 to 950degC, depending on the crystal orientations. Together with their temperature-independent properties, ReCOB crystals are promising candidates for sensing applications at elevated temperatures.