Role of oxygen pressure on the stability of lanthanum strontium manganite–yttria stabilized zirconia composite

We have investigated the structural and chemical stability of La0.8Sr0.2MnO3 (LSM)–8 mol.% yttria stabilized zirconia (YSZ) composite. LSM and YSZ powders were mixed and sintered at 1400 °C for 10 h in controlled atmosphere (PO2 = 0.21 to 10−6 atm). The unit cell volume of LSM increases during exposure to reduced oxygen partial pressure while it remains unchanged for YSZ. During reduction in the oxygen partial pressure from 0.21 atm to 10−6 atm, the solubility of manganese in YSZ increases from ∼10 at.% to ∼15 at.%. Lower oxygen partial pressure also results in the grain growth and formation of La2Zr2O7 and MnOx (Mn3O4) compounds lowering the stability of the LSM–YSZ composite. On subsequent sintering in 0.21 atm PO2, the La2Zr2O7 and MnOx compounds tend to disappear indicating the reversibility of the interaction. The reversibility of LSM–YSZ reaction has been independently confirmed using La2Zr2O7 and MnOx.