The lauric acid (LA)/diatomite composite phase change materials (PCMs) were prepared using a direct impregnation method, in which LA was chosen as PCM. The chemical structure, chemical compatibility, element composition, crystalline structure, thermal properties and thermal stability of LA/diatomite composite were extensively investigated by Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry and thermal gravimetric analysis. FTIR and XRD results indicate that there are only physical interactions between LA and diatomite in LA/diatomite composite. The decrease of XRD intensity of composite PCM confirms the reduction of the crystalline size of LA in LA/diatomite composite. The melting and freezing temperatures of composite PCM are 40.9 degrees C and 38.7 degrees C respectively. The latent heat of composite PCM is 57.2 J/g. LA/diatomite composite does not decompose when the surrounding temperature is lower than 157 degrees C, indicating that the composite PCM has a good thermal stability. (C) 2015 Published by Elsevier B.V.