High temperature piezoelectric single crystal ReCa4O(BO3)3 for sensors

Large size and high quality ReCa₄O(BO₃)₃ 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 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 2times10⁸ Ohm.cm at 800degC, with Q values of >4,500 at 950degC. The frequency/temperature coefficient of YCOB was found to be -75 ~ -85 ppm/K in the temperature range of 30-950degC, depending on the crystal orientation. Together with its temperature independent properties, ReCOB crystals are promising candidates for sensing applications at elevated temperatures.