ULTRASONIC PROPERTIES OF Bi₁₂GeO₂₉ CRYSTAL

Temperature dependences of ultrasonic longitudinal wave attenuation have been measured for bismuth germanium oxide in th 110 and 111 directions from 4.2 K to 300 K using ultrasonic pulse echo technique. There is a large anomalous absorption peak in the vicinity of 50 K in the 110 and 111 directions. This behavior indicates an activated relaxation process of Bi₁₂GeO₂₀ crystal itself.
The sound velocities of longitudinal and shear waves in Bi₁₂GeO₂₀ crystal have accurately been measured in the 100, 110 and 111 directions with pulse-echo-overlap (PEO) technique anh the elastic constants C₁₁,C₄₄ and C₁₂ have been determined.