Low-temperature elastic coefficients of polycrystalline indium

Using an ultrasonic pulse-echo method, we measured the elastic coefficients of polycrystalline indium from 300 to 5 K. All elastic coefficients showed regular temperature behavior, as predicted by an Einstein-oscillator model. The shear and Young moduli showed the largest change, increasing ≈55% during cooling. The Poisson ratio was unusually high at 0.45, just below the theoretical upper bound of 0.5. Using a Marx composite oscillator, we measured the internal friction at room temperature. We calculated the acoustic Debye temperature, 108.4 K, that agreed well with a monocrystal acoustic value, 111.3 K and the specific-heat value, 108.8 K. Also, we calculated the Grüneisen parameters, γL=2.04, γH=2.68, that agreed well with the specific-heat value, γ=2.48 and the shock-wave value, γ=2.24.