Piezospectroscopic Analysis of the Residual Stresses in the Strontium Hexaluminate/Zirconia (SrAl12O19/ZrO2) System

Samples of strontium hexaluminate (SrAl 12 O 19 ), both pure and mixed with different amounts of ceria‐stabilized zirconia (CE‐TZP), have been prepared via a chemical route. The fluorescence spectrum of SrAl 12 O 19 is similar to that of ruby and yttrium aluminium garnet (YAG); consequently, this similarity has been attributed to the presence of a trace impurity of Cr 3+ ions. The most‐intense fluorescence peak of SrAl 12 O 19 exhibits a dependence on stress that is given by the average uniaxial piezospectroscopic coefficient (<Pi> = 1.5 cm ‐1 ·GPa ‐1 ). The piezospectroscopic coefficient has been used to convert to stress the fluorescence frequency shift of SrAl 12 O 19 mixed with zirconia (ZrO 2 ). The stress, as a function of the volume fraction of ZrO 2 , resides between the Hashin‐Shtrikman bounds but is best reproduced by an effective medium approximation.