Hysteretic and time dependent deformation of plasma sprayed zirconia ceramics

The effect of microstructural evolution on hysteresis loss and time dependent deformation of air plasma sprayed 7 wt.% Y₂O₃ stabilized ZrO₂ coating has been studied after isothermal exposure between 800–1300 °C. Miniaturized cantilevers prepared from free-standing heat-treated coatings were loaded using a nanoindenter. Both, the hysteresis loss during cyclic loading and the creep displacement at fixed load show two domains of behavior with respect to heat treatment: a low temperature/time domain wherein the hysteresis loss and the maximum creep displacement drop significantly without measurable change in density, and a high temperature domain in which both parameters decrease more gradually but accompanied by significant densification. Both phenomena are attributed to the partially reversible sliding of interfaces driven by shear stresses that are developed at pores and micro-cracks, as shown by finite element analysis.