Piezospectroscopic study of residual stresses in ZrO2/Al2O3 composites

The residual stresses in Ce-ZrO2/Al2O3 composites having 0 - 90 vol. % of alumina were measured by piezospectroscopic techniques. The compressive stress in Al2O3 was determined from the frequency shift of the R2 luminescence band using the well-known piezospectroscopic coefficient. The tensile stress in t-ZrO2 has been found in two ways. At the first one, it has been derived from the equilibrium of forces in a free-standing piece of two-phase material. In the second, the frequency shift of Raman band of t-ZrO2 have been plotted against the calculated stress and the slopes provided the PS coefficients. Having the PS coefficients, the stress in t-ZrO2 was calculated from the known relationship between frequency shift and the stress state to which the material is subjected. The PS coefficients obtained show a good agreement with those previously published by other researchers on a more limited set of compositions. In a result a new simple method for the determination of the piezospectroscopic coefficients of Raman bands of materials is proposed, which does not require neither loading devices nor sample machining. The effect of residual stresses on mechanical properties of composites is discussed. (author)