Low-temperature elastic and piezoelectric constants of paratellurite (α-TeO2)

We report paratellurite’s 300-10-K elastic constants Cij, six constants reflecting tetragonal symmetry (P422 point group). The quantity e142∕k11, where e14 denotes the sole independent piezoelectric constant and k11 denotes a dielectric constant, was determined over the same temperature range. All the principal Cij show approximately regular temperature-change behavior: increasing with decreasing temperature, the increases being 2%–10%. One derived elastic constant, C′=(C11−C12)∕2, a shear constant, shows strongly anomalous temperature behavior, decreasing continuously during cooling to 10K, the total decrease being 5%. The quantity e142∕k11 was essentially independent of temperature. Obtained by resonant-ultrasound spectroscopy, our results differ from previous studies, none of which went to 10K, a temperature region of much practical interest for this material. From the near-zero-temperature elastic constants, we derive a Debye temperature of 235K. The slope dC′∕dT yields a negative Gruneisen parameter γ=−0.9, close to the specific-heat value.