Anomalous shrinkage of strontium doped lanthanum manganite

The extent of anomalous shrinkage behavior of porous Sr-doped Ianthanum manganite (La1-xSrx)1-y MnO3+δ, or LSM-X, where x = 0.0 to 0.4 and X = x% was studied as a function of Sr concentration, thermal, and oxygen partial pressure (pO2) cycling. The shrinkage or densification of LSM was induced by either thermal cycling between 650⁰C and 1000⁰C at a constant oxygen partial pressure (air), or at a fixed temperature between 650⁰C and 1000⁰C while cycling the pO2 between air and nitrogen (0.2 x 10-5 atm O2). Thermal cycling LSM-10 (x = 0.1) between 800uC and 1000uC resulted in the maxi mum thermal cycling shrinkage rate. Cycling the ambient pO2 of an LSM-10 bar at 900°C resulted in the maximum shrinkage rate with a cycling time of two minutes. Throughout each of the thermal or pO2 cycling tests LSM never attained an oxygen stoichiometry equiIibrium state corresponding to its temperature and pO2. It was postulated that the transition between these non-equiIibrium oxygen nonstoichiometry states was Iinked to the anomalous shrinkage of LSM --Abstract, page iii