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High-Temperature Electromechanical Characterization of AlN Single Crystals
Kim, T., Kim, J., Dalmau, R., Schlesser, R., Preble, E., & Jiang, X. (2015). High-Temperature Electromechanical Characterization of AlN Single Crystals. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 62(10), 1880-1887. https://doi.org/10.1109/TUFFC.2015.007252
AlN is a non-ferroelectric material and does not have any phase transition up to its melting point (>2000 degrees C), which indicates the potential use of AlN for high-temperature sensing. In this work, the elastic, dielectric, and piezoelectric constants of AlN single crystals were investigated at elevated temperatures up to 1000 degrees C by the resonance method. We used resonators of five different modes to obtain a complete set of material constants of AlN single crystals. The electrical resistivity of AlN at elevated temperature (1000 degrees C) was found to be greater than 5 x 10(10) Omega . cm. The resonance frequency of the resonators, which was mainly determined by the elastic compliances, decreased linearly with increasing temperature, and was characterized by a relatively low temperature coefficient of frequency, in the range of -20 to -36 ppm/degrees C. For all the investigated resonator modes, the elastic constants and the electromechanical coupling factors exhibited excellent temperature stability, with small variations over the full temperature range,
