Ultrasonic Microspectroscopy of Ultra-High-Quality Synthetic a-Quartz

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Ultrasonic microspectroscopy technology, using the line-focus-beam (LFB) and plane-wave (PW) ultrasonic material characterization (UMC) system, has been applied to establish evaluation techniques for synthetic α-quartz crystals for bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices and to accurately measure the acoustical physical constants. The purpose of this study was to provide a new, worldwide guideline and standard for synthetic α-quartz in the industrial and scientific fields.1. Measurement accuracies of the LFB ultrasonic material characterization system and bulk ultrasonic spectroscopy system have been improved.2. Development of new methods for determining the acoustical physical constants of class-32 crystals and determination of the constants of synthetic and natural α-quartz:(1) A new BAW method to accurately determine all of the independent components of the acoustical physical constants for class-32 crystals was developed. This method requires to measure lon … More gitudinal and shear velocities, dielectric constants, and density, using X-, Y-, and Z-cut specimens and several rotated Y-cut specimens. The demonstration was conducted for SAW-grade synthetic α-quartz. The results provided the constants that give BAW velocities within an accuracy of ±0.2 m/s (±0.004%).(2) To compare the acoustic properties between natural and synthetic α-quartz, longitudinal and shear velocities, and LSAW velocities were measured using X-, Y-, and Z-cut specimens. All the velocity differences were within 1.00 m/s, and it was clarified that the acoustical physical constants of the natural quartz, were, very similar to those of synthetic quartz.(3) Another new method for determining all the constants for class-32 crystals by measuring LSAW velocities in addition to BAW velocities for there principal X-, K and Z-cut specimens using the LFB/PW UMC system was developed. This method was applied for natural α-quartz.(4) Precise values of the constants for natural quartz were also determined using the BAW method developed here.3. BAW velocities. LSAW velocities, density and lattice parameters were measured for the specimens prepared from several synthetic α-quartz crystal ingots with different growth conditions. Slight velocity differences were detected. The velocity changes related to the impurity concentration, especially OH content, were different for the propagation directions and propagation modes. Lattice constant a was constant, but c became larger as the OH content became higher. Less