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High-Temperature Electromechanical Characterization of AlN Single Crystals

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,

Citation

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. DOI: 10.1109/TUFFC.2015.007252

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