Mg2FeH6 was synthesized by ball milling MgH2 and Fe (2:1 molar ratio) mixture for 72 h followed by heating at 400 degrees C under H-2 pressure. The hydride formation, its structure and homogeneity were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Raman spectroscopy. High pressure in situ synchrotron X-ray diffraction and Vienna ab initio simulation were used to determine bulk modulus of the sample. The bulk modulus of Mg2FeH6 was found to be 75.4(4) GPa by optimized experiment and 76.3 GPa by theoretical simulation. From high temperature in situ X-ray diffraction study the volumetric thermal expansion coefficient of Mg2FeH6 was found to be alpha(upsilon) = 5.85(3) x 10(-5) + 7.47(7) x 10(-8) (T - T-o)/degrees C. Decomposition of Mg2FeH6 was observed at 425 degrees C and the decomposition products were Mg, Fe and H-2. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.