The Bulk Acoustic Wave Properties of Lithium Tetraborate

Abstract

Lithium tetraborate is a new piezoelectric material which has been shown to have improved properties for SAW applications. In view of this the bulk acoustic wave properties have been predicted for both singly and doubly rotated cuts, using the values of the material constants and their temperature coefficients currently available. One of the orientations investigated showed potentially interesting properties. An Xz-cut rotated 5640' about X1 displayed a zero room temperature first order temperature coefficient of frequency for the thickness shear mode. Although there is strong coupling to a thickness extensional mode this is well separated out in frequency and the response is effectively single moded. The piezoelectric coupling constant for the thickness shear mode was predicted to be greater than 6%, comparing favourably with AT quartz (0.8%) and 28 rotated berlinite (3%). Preliminary measurements on single resonator devices have been conducted. The existence of a parabolic frequencyltemperature performance has been confirmed with second order temperature coefficient of