Gas-phase triggered phase evolution in pressure-less sintered LiF doped Mg-Al spinel

Abstract

Within the studies of the LiF-MgAl2O4 system, a dissolution - reprecipitation process is postulated at high pressure synthesis, involving LiAlO2 and MgF2 as transient phases. Heating experiments at atmospheric pressure, combined with a dedicated sample geometry enabled the identification of LiAlO2 and MgO via XRD and, for the first time, with electron microscopic examinations. Moreover, it is shown that a second generation of spinel precipitates as the result of a gas-phase reaction. The involvement of a gaseous phase is seen as the major reason, why it seems impossible to produce transparent spinel in a pressure-less sintering regime.