  Thermal decomposition behaviors of TiH2 powder under a flowing helium
atmosphere and in a low vacuum condition have been studied by using in-situ
EXAFS technique. By an EXAFS analysis containing the multiple scattering paths
including H atoms, the changes of hydrogen stoichiometric ratio and the phase
transformation sequence are obtained. The results demonstrate that the initial
decomposition temperature is dependent on experimental conditions, which
occurs, respectively, at about 300 and 400 degree in a low vacuum condition and
under a flowing helium atmosphere. During the decomposition process of TiH2 in
a low vacuum condition, the sample experiences a phase change process:
{\delta}(TiH2) - {\delta}(TiHx) - {\delta}(TiHx)+{\beta}(TiHx) -
{\delta}(TiHx)+{\beta}(TiHx)+{\alpha}(Ti) - {\beta}(TiHx)+{\alpha}(Ti) -
{\alpha}(Ti)+{\beta}(Ti). This study offers a way to detect the structural
information of hydrogen. A detailed discussion about the decomposition process
of TiH2 is given in this paper.
