In recent years LiGaO2 has been gaining attention as a substrate material for the growth of GaN. Since film deposition is generally carried out at high temperatures the behavior of the substrate at processing temperatures should be known. The lattice constants of polycrystalline LiGaO2 were measured from room temperature to 1423 K and the linear thermal expansion coefficients in the temperature range between 293 and 1423k were determined to be alpha (a) = 10.1 +/- 0.2 x 10(-6) K-1, alpha (b) = 21.1 +/- 0.3 x 10(-6) K-1, and alpha (c) = 13.6 +/- 0.2 x 10(-6) K-1. High temperature X-ray powder diffraction data show that at above 1173 K the Ga rich phases, LiGa5O8 and Ga2O3, start to form indicating volatilization of the Li from the structure.