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High-Temperature Electroacoustic Characterization of Y-Cut and Singly-Rotated Ca3TaGa3Si2O14 Resonators



Ward L. Johnson, Michal Schulz, Holger Fritze


Synthetic piezoelectric crystals in the P321 crystal class have been a focus of substantial research that is largely driven by applications in high-temperature resonant bulk-acoustic- wave (BAW) and surface-acoustic-wave (SAW) sensing. Fully ordered crystals in this class, such as Ca3TaGa3Si2O14 (CTGS), have been suggested as offering the potential of electroacoustic performance that is superior to more extensively studied langasite (LGS) and langatate (LGT), which are partially disordered. In this study, the resonant frequencies, acoustic damping, and electrical conductivity of CTGS bulk acoustic resonators with Y-cut and (YXl) −30° crystal orientations and fundamental frequencies near 5 MHz are investigated at temperatures between ambient and 1100 °C. (YXl) −30° resonators are found to have turnover temperatures near 200 °C for the third and fifth overtones, in contrast to a monotonic decrease in resonant frequencies of Y-cut crystals with increasing temperature. The maximum temperature derivative of fractional changes in fifth-overtone frequency of (YXl) −30° CTGS is 40e−6/K (near 1100 °C), and this value is not greatly different from the temperature derivative of Y-cut CTGS frequencies over a broader range of temperatures. At ambient temperatures, the acoustic loss 1/Q of CTGS with both crystal orientations is found to be greater than the lowest values previously reported for LGS and LGT. The electrical conductivity of the CTGS samples between 500 °C and 1100°C is substantially lower than that previously reported for LGS. Corresponding to this lower conductivity, the piezoelectric/conductivity contribution to 1/Q at elevated temperatures is reduced. Additional anelastic relaxation peaks observed between 100 °C and 700 °C are similar to those previously reported for LGS and LGT.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control


acoustic properties, acoustic resonators, anelastic relaxation, anelasticity, BAW resonators, Ca3TaGa3Si2O14, CTGS, elasticity, electrical conductivity, high-temperature sensors, langasite, langatate, LGS, LGT, , quality factor, temperature compensation, temperature dependence


Johnson, W. , Schulz, M. and Fritze, H. (2014), High-Temperature Electroacoustic Characterization of Y-Cut and Singly-Rotated Ca3TaGa3Si2O14 Resonators, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, [online], (Accessed April 20, 2024)
Created July 26, 2014, Updated November 10, 2018