Polar lattice dynamics of the MgAl2O4 spinel up to the liquid state

Emittance spectra of the MgAl2O4 spinel have been obtained up to 2500 K. Spectral analysis using a dielectric function model recently developed for amorphous materials allowed us to retrieve the inversion parameter over a very wide temperature range. The results are very close to the most recent published values. Both the Landau and the O'Neill and Navrotsky thermodynamic models allow a satisfactory fit to the experimental data. In the mid-infrared range, a sudden increase of the emittance appears more than 200 degrees below the solid to liquid transition. The mechanism of absorption is very well described by a Debye process for which both dielectric contribution and relaxation time are thermally activated. Finally, we showed that the change of phase leads to an abrupt modification of the lattice dynamics and that change evolves rapidly in the liquid state.