The crystal structure (Cmmm, a = 773.50, b = 1093.6, c = 382.58pm) of quenched samples of this high-temperature phase, which was stable at temperatures of between 668 and 749K, was determined by applying X-ray diffraction techniques to powders or twinned crystals. It was found that 6 individual twins were connected by one 3-fold rotation axis and by 3 two-fold rotation axes. Raman spectra and ionic conductivity data revealed that the present material was very similar to orthorhombic low-temperature forms of Li2MgBr4 and Li2MnBr4. High-temperature X-ray and neutron diffraction studies of quenched powder samples revealed the formation of an inverse spinel-type polymorph (Fd¯3m, a = 1115.2pm) at temperatures ranging from 441 to 668K.

M.Partik, C.Wickel, H.D.Lutz, T.Roisnel: Journal of Solid State Chemistry, 1996, 124[2], 292-9