Sm2+ fluorescence and absorption in cubic BaCl2: Strong thermal crossover of fluorescence between 4f6 and 4f55d1 configurations

► Strong red 5d emission matched to semiconductor-based radiation detectors. ► Stabilisation of the high temperature cubic phase of Sm-doped BaCl2 at 295 K. ► Dramatic temperature-induced intensity transfer between 5d and 4f PL emissions. ► Most comprehensive model yet achieved of Sm PL temperature dependence. ► Successful modelling of absorption spectra by an extended crystal field calculation.