Influence of Oxygen Partial Pressure during Growth on Optical and Electrical Properties of Ca3TaAl3Si2O14 Single Crystals

Among the langasite family, Ca3TaAl3Si2O14 (CTAS) is particularly promising for high temperature sensor applications due to its relatively high resistivity. In this work, CTAS single crystals have been grown by the Czochralski technique under various oxygen partial pressures using Ir and Pt crucibles. Colorless CTAS crystals were grown for the first time; however, the elimination of related defects did not influence the electrical properties. Furthermore, dielectric and piezoelectric properties were independent of growth conditions. Instead, the electrical resistivity was found to be remarkably higher the lower the oxygen partial pressure, reaching a value of ∼7 × 1010 Ω cm at 400 °C, which is 3 orders of magnitude higher than that of disordered LTGA. Therefore, grown CTAS crystals are promising for high temperature piezoelectric sensor applications.