Stress-induced diffusion and defect chemistry of La0.2Sr0.8Fe0.8Cr0.2O3−δ: Part 1—creep in controlled-oxygen atmosphere

In this study, the compressive creep behavior of La0.2Sr0.8Fe0.8Cr0.2O3−δ (LSFCO) in oxygen-controlled atmosphere is investigated in order to understand the underlying stress-induced cation diffusion and defect chemistry in this compound. The creep behavior is investigated in the stress, temperature and grain size ranges of 10–80 MPa, 1100–1175 °C and 3.2–28.5 μm, respectively. The oxygen atmosphere is controlled in the oxygen partial pressure range of PO2=0.21–10−14 atm. The material exhibits two markedly different behaviors at high and low PO2. At high PO2, the behavior is characterized by the oxygen partial pressure exponent of m=0.04, followed by a drastic increase in strain rates at low PO2, characterized by m=−0.5. In the m=−0.5 regime, the effect of oxygen partial pressure on the grain size exponent, as well as the transition to power-law creep is investigated. It is concluded that the mechanism responsible for the rapid increase in strain rates increases the contribution of bulk diffusion from predominant (p=2.3) to nearly pure bulk diffusion (m=2.07). The same mechanism also increases the stress range for predominant diffusion creep relative to power-law creep.