Low-temperature acoustic properties of single-crystal hafnium

Abstract

Five independent adiabatic elastic tensor components c _ij of single-crystal Hf (0.3% Zr) have been precisely measured in the range 78–300 (c ₁₁ and c ₃₃) or 78–160 K (c ₁₂, c ₁₃, and c ₄₄) at 50 MHz using an ultrasonic pulse technique. The corresponding linear absorption coefficients α _ij (T) have been measured in the same temperature ranges. The c _ij data have been used to determine adiabatic compressibilities β_∥ and β_⊥, and Young’s moduli E _∥ and E _⊥ along and across the c axis, respectively. Near 140 K, we have revealed an anomaly in c ₃₃(T) due to changes in the phonon spectrum of single-crystal α-Hf. The observed anomalies in temperature-dependent α₁₁ and α₃₃ are tentatively attributed to grown-in dislocations.