Temperature dependence (13-600 K) of Mn4+ lifetime in commercial Mg28Ge7.55O32F15.04 and K2SiF6 phosphors

The fluorescence lifetime of the Mn4+2Eg→4A2g transition in commercial Mg28Ge7.55O32F15.04 (MFG) and K2SiF6 (KSF) phosphors are measured in the temperature region of 13-600 K. In MFG, the observed decrease in the lifetime with increasing temperature is correlated with increasing probability of phonon induced transitions (vibronic emission) without any contribution of nonradiative transitions. In KSF, the decrease in lifetime in the temperature region of 13-500 K is associated with an increase in the vibronic transition probability. Above 500 K, the rapid decrease in the lifetime is correlated with the onset of non-radiative relaxation. The differences between the thermal quenching behavior of Mn4+ luminescence in the two phosphors in explained with respect to the energy position of the 4T2g state.