In-situ X-ray diffraction, differential scanning calorimetry and dilatometry were used to measure the thermal expansion and thermal stability of cerium-doped Lu2SiO5. The thermal expansion of Lu2SiO5 was highly anisotropic, with expansion along the b- and c-axes 5-10 times greater than expansion along the a-axis. There were no measurable differences in the thermal expansion between undoped Lu2SiO5, cerium-doped Lu2SiO5 with high scintillation efficiency, cerium-doped Lu2SiO5 with low scintillation efficiency and annealed cerium-doped Lu2SiO5. Lu2SiO5 decomposed at temperatures as low as 1350 degrees C in < 1 ppm O-2, while the presence of 100-150 ppm O-2 stabilized Lu2SiO5 at temperatures up to 1760 degrees C. No bulk defects were identified to account for th(e) difference between high scintillation efficiency and low scintillation efficiency cerium-doped Lu2SiO5 samples. Published by Elsevier Ltd.