Bulk modulus and thermal expansion coefficient of mechano-chemically synthesized Mg sub(2FeH) sub(6) from high temperature and high pressure studies

Mg sub(2FeH) sub(6) was synthesized by ball milling MgH sub(2 and Fe (2:1 molar ratio) mixture for 72 h followed by heating at 400 degree C under H) sub(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 Mg sub(2FeH) sub(6) 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 Mg sub(2FeH) sub(6) was found to be alpha sub(v = 5.85(3) x 10) super(-)5 + 7.47(7) x 10 super(-8 (T - T) sub(o))/ degree C. Decomposition of Mg sub(2FeH) sub(6) was observed at 425 degree C and the decomposition products were Mg, Fe and H sub(2.)