The line-focus-beam ultrasonic material characterization (LFB-UMC) system is applied to compare and evaluate tolerances provided independently for the Curie temperature T C and lattice constant a to evaluate commercial LiTaO 3 single crystals by measuring the Rayleigh-type leaky surface acoustic wave (LSAW) velocities V LSAW. The relationships between V LSAW, and T C and a measured by individual manufacturers were obtained experimentally using 42°YX-LiTaO 3 wafers as specimens from three crystal manufacturers. In addition, the relationship between V LSAW and SH-type SAW velocities V SAW that are actually used for the SAW device wafers was obtained through calculations, using the chemical composition dependences of the acoustical physical constants for LiTaO 3 crystals reported previously. The result of a comparison between the T C tolerance of ±3°C and the a tolerance of ±0.00002 nm through the common scale of V LSAW or V SAW demonstrated that the a tolerance is 1.6 times larger than the T C tolerance. Furthermore, we performed a standardized comparison of statistical data of T C and a for LiTaO 3 crystals grown by two manufacturers during 1999 and 2000, using V LSAW. The results clarified the differences of the average chemical compositions and of the chemical composition distributions among the crystal ingots between the two manufacturers. A guideline for the standardized evaluation procedure has been established for the SAW-device wafer specifications by the LFB-UMC system.
|ジャーナル||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|出版ステータス||Published - 2002 4月|
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