Bulk modulus and thermal expansion coefficient of mechano-chemically synthesized Mg2FeH6 from high temperature and high pressure studies

Mg2FeH6 was synthesized by ball milling MgH2 and Fe (2:1 molar ratio) mixture for 72 h followed by heating at 400 °C under H2 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 αv = 5.85(3) × 10−5 + 7.47(7) × 10−8 (T − To)/°C. Decomposition of Mg2FeH6 was observed at 425 °C and the decomposition products were Mg, Fe and H2.