Ultrasonic investigation of the nonlinearity of fused silica for different hydroxyl-ion contents and homogeneities between 300 and 3°K

The harmonic-generation technique was used to measure the third-order elastic constants C₁₁₁ of four types of fused silica. The samples differed in amount of OH content and directional homogeneity. The results indicate that a relatively large OH content in fused silica may give rise to a relatively greater value of C₁₁₁ and that C₁₁₁ is a weak function of temperature regardless of OH content. The relationship between the experimentally defined ultrasonic nonlinearity parameter β=-(3C₁₁+C₁₁₁)3C₁₁ and the Gr\"uneisen parameter γ also has been determined. The measured temperature dependence of β indicates that in the Debye model elastic constants other than C₁₁ and C₁₁₁ must dominate the strong temperature dependence of the Gr\"uneisen parameter for fused silica at low temperatures.