Single phase materials of the La(2-x)SrxMnO4 +/-delta (0.6 <= x <= 2.0) solid solution series were prepared via solid state reaction. The structure of each material was examined at room temperature and determined to be tetragonal for all phases examined. An expansion in lattice volume was observed on increasing lanthanum content. The stability and thermal expansion of each member of the solid solution series was determined via the use of in situ high temperature X-ray diffraction. It was found that all materials remained stable up to a temperature of 800 degrees C. Thermal expansion coefficients were found to be in the region of 15 x 10(-6) K-1 for La(2-x)SrxMnO4 +/-delta compounds where x > 1.4. The electrical conductivity of each phase was also determined over a similar temperature range with a maximum value of similar to 6 Scm(-1) at 900 degrees C for the x=1.8 phase. (c) 2006 Elsevier B.V. All rights reserved.