Time dependent deformation of LaCoO ₃ based perovskites at different temperatures: ferroelastic and non-ferroelastic creep behaviour

Analysis of the creep behaviour of ferroelastic LaCoO ₃ and La _0.8 Ca _0.2 CoO ₃ perovskites at room and elevated temperatures is presented. It was found that the creep behaviour of the two LaCoO ₃ -based compositions was determined by ferroelastic and non-ferroelastic creep strain components. Both the ferroelastic and non-ferroelastic creep strain components showed a strong dependence on bending stress. The ferroelastic creep depends on the coercive stress in LaCoO ₃ based perovskites, which in turn is a function of temperature. In addition, the ferroelastic creep strain has the same sign as the total strain of cobaltites upon loading, however, it has the opposite sign relative to the total strain upon unloading. Non-ferroelastic creep was negligibly small in both perovskites at low temperatures, however, its contribution toward the total creep increased significantly at elevated temperature. Non-ferroelastic creep strain has the same sign as the total strain both upon loading and upon unloading.