Investigation of langanite and langatate single crystals for high temperature sensing

La₃Ga_5.5Nb_0.5O₁₄ (LGN) and La₃Ga_5.5Ta_0.5O₁₄ (LGT) with trigonal 32 symmetry were grown by Czochralski (CZ) method. High Resolution X-Ray Diffraction (HRXRD) measurement was carried out on the as-grown LGN and LGT crystals for crystal quality evaluation. Frequency temperature dependent behaviors were investigated to explore the zero temperature coefficient of frequency (TCF) cuts at elevated temperature. Among the investigated crystal cuts, (XYt)θ cuts with length extensional vibration mode (LEM) were found to possess high turnover temperature around 250°C, for LGN and LGT crystals. Moreover, LGN (YXl)15° and LGT (YXl)20° crystal cuts, taking advantage of thickness shear vibration mode (TSM), were found to exhibit strong frequency stability in the temperature range of 20~400°C, with turnover temperatures at 280°C and 180°C, respectively. The high electromechanical coupling factor k (>;10%), high mechanical quality factor Q (>;4000), together with the zero TCF characteristics at elevated temperature, indicating LGN and LGT crystals potential for high temperature (100~400°C) sensing applications.