The mechanisms of thermal expansion and shrinkage for sintered La0.8Sr0.2MnO3+delta samples, with different relative densities, have been investigated in air during thermal cycle measurements between 50 and 1100 degrees C. The perovskite samples showed a large thermal expansion coefficient (TEC) at approximately 42 degrees C due to a change from monoclinic and hexagonal phases to a single hexagonal one. The TEC of the porous samples with initial relative densities < 88% decreased at temperatures > 85 degrees C and continued to shrink during thermal cycling up to approximately 1000 cycles. The dense samples with relative densities. 88% showed no shrinkage during thermal cycling, and their TEC increased monotonically with increasing temperature. It was found that the shrinkage rates of the samples showed a linear dependency on their initial relative density and had a tendency to decrease with increasing the heating/cooling rate. (c) 2005 The Electrochemical Society.