Temperature Compensated Cuts of Berlinite and B-Eucryptite for SAW Devices

Abstract

Abstract : Calculations of the surface acoustic wave (SAW) properties of berlinite (AlPO4) and beta-eucryptite (beta-LiAlSiO4) show that both materials are temperature compensated along both singly rotated and doubly rotated orientations. For berlinite, several orientations combine zero electromechanical power flow angles with more than four times the piezoelectric coupling of ST cut quartz. The best singly rotated orientation is a direct analog of the ST cut of quartz. This cut has, like ST quartz, a zero electromechanical power flow angle, but the distinct advantage of more than four times the piezoelectric coupling. For beta-eucryptite, a singly rotated orientation has a SAW velocity of 3662 m/sec and almost twice the piezoelectric coupling of ST cut quartz, but the disadvantage of an electromechanical power flow angle of 18 degrees. The results for berlinite show that it represents an attractive alternative to quartz for use in broadband, low insertion loss SAW devices. The relatively low piezoelectric coupling of beta-eucryptite makes it unattractive for broadband, low insertion loss applications, but its relatively large SAW velocity indicates that it may be useful in high frequency applications.