Shrinkage behavior of La1-xMnO3+δ perovskites (0≤x≤0.1) by phase change during thermal cycling in air

The shrinkage mechanism of nondoped lanthanum manganite perovskites, La1-xMnO3+delta (0less than or equal toxless than or equal to0.1), during a thermal cycling in air has been investigated. For the La1-xMnO3+delta samples annealed at 600degreesC, they shrank during a thermal cycle measurement in the temperature range from 600 to 1100degreesC, and a decrease of their linear thermal expansion coefficients at temperatures > around 940degreesC was observed. It was found during the thermal cycle measurement in the temperature range from 50 to 800degreesC that the LaMnO3+delta sample quenched from 1000degreesC exhibited a large shrinkage at around 700degreesC by phase change from the orthorhombic into the hexagonal perovskite. For the La0.95MnO3+delta and La0.9MnO3+delta perovskite samples without the phase change, no shrinkage behavior was observed.