ULTRASONIC PROPERTIES OF BISMUTH GERMANIUM OXIDE

Abstract

Temperature dependence of the elastic wave losses is reported for bismuth germanium oxide, Bi12GeO20, a strongly piezoelectric crystal of point group 23. At 296°K and at 500 Mc/sec the attenuation, Γ, is 0.11 dB/μsec and at 118 Mc/sec is 0.008 dB/μsec. At 4.2°K and at 500 Mc/sec, Γ is 5 × 10−4 dB/μsec and at 118 Mc/sec is 2.7 × 10−4 dB/sec. At intermediate temperatures five loss peaks are observed, the origins of which as yet have not been determined. A shear wave velocity and the longitudinal wave velocity in the [110] direction are 1.77 × 105 and 3.42 × 105 cm/sec, respectively. The low elastic wave velocities and loss in Bi12GeO20, the low crystallization temperature, the piezoelectric coupling and the fact that it is cubic suggest possible advantages for device application involving storage of information at vhf and microwave frequencies.