In Situ Synchrotron Powder X-ray Diffraction Studies of the Thermal Decomposition of β- and γ-AlD3

Abstract

Details of the thermal decomposition of β-AlD3 and γ-AlD3 have been investigated by in situ synchrotron X-ray diffraction at a constant heating rate of 1 K/min and isothermally in dynamical vacuum. The β-AlD3 transforms into α-AlD3 prior to decomposing to Al and D2. The transformation into α-AlD3 starts at about 80 °C, and the decomposition to Al and release of D2 starts at 130 °C. The transformation of γ-AlD3 into α-AlD3 starts at about 90 °C, and the sample decomposes to Al and D2 at a higher temperature (from about 130 °C). From about 110 °C, γ-AlD3 also decomposes directly into Al and D2. Detailed analyses of the changes in unit cell dimensions during the decomposition for all phases have been performed in order to propose possible routes for the transitions.