Refined crystal field model for the piezospectroscopy analysis of stresses in polycrystalline alumina

摘要

Stresses produce systematic shifts in the R-line luminescence from Cr~(3+) ions in aluminium oxide. The two calculational models for determining the stress from observed R-line shifts are compared and combined with new measurements, made under a variety of different stress conditions, to determine refined crystal field model parameters for the piezospectroscopic shifts with stress. In addition to previous, well established results, it is found that the R2-luminescence line shifts linearly with the hydrostatic component of stress, (σ_(11) + σ_(22) + σ_(33)), even under non-hydrostatic stresses. The separation of the R1 and R2 lines is not linear with the non-hydrostatic stress and increases from biaxial to uniaxial stress states. Excellent agreement with experimental data for polycrystalline materials under uniaxial and biaxial stresses was found when averaging the stresses using the Voigt approximation. However, the R2-R1 peak separation may be affected by the stress dependence of the spectral shape or stress relaxation under the highest stresses.