Elastic Properties of Polycrystalline Monoclinic Gd ₂ O ₃

The elastic properties of polycrystalline monoclinic Gd 2 O 3 were determined by the sonic‐resonance method. Volume‐fraction porosity varied from 0.025 to 0.367 and temperature from room temperature to 1400°C. The Young's and shear moduli are linear functions of volume‐fraction porosity, but the rate of their decrease with increasing porosity is less than that expected. The moduli decreased more rapidly than expected with increasing temperature. The Debye temperature is 362°K. With increasing temperature, the first Grueneisen constant, γ, decreases, whereas the second Grueneisen constant, δ, increases.