Time-dependent recovery of the elastic modulus in thermally shocked polycrystalline yttrium iron garnet (YIG)

Thermal shock damage is typically characterized by “single quench-fracture tests” in which a specimen is quenched a single time into a water bath, then fractured. However, technical ceramics, such as engine components, solar collectors and ceramic computer memory substrates, must tolerate repeated thermal shocks under service conditions. Therefore, the understanding of damage induced by multiple thermal shocks is very important. Thermal shock damage caused by repeated thermal fatigue in yttrium iron garnet (YIG) was monitored by nondestructive elasticity measurements for each cycle of shock. For a relatively low level of shock-induced damage, an unexpected time-dependent recovery of the elastic modulus at room temperature was observed, and successfully characterized by a non-homogeneous, linear, first-order differential equation.