Non-radiative processes and luminescence quenching in Mn4+ doped phosphors

We present the temperature dependence of the E-2 -> (4)A(2) emission of Na2TiF6:Mn4+. Our results are discussed in the framework of the single configurational coordinate diagram (SCCD) model proposed by Struck and Fonger. We have critically analyzed the SCCD model and calculated the vibrational overlap integrals directly from the Manneback recurrence formulas. We have considered the physical origin of shift of the excited state parabolae in the configurational space as well as possible different slopes of the ground and excited electronic manifolds. We have compared our results with numerous results obtained for Mn4+ in other lattices available in the literature. We have found the high inconsistency between the experimental results and values obtained under the SCCD model. Moreover, we have found strong correlation between the values of experimental activation energies E-nr. and values of constant describing the probability of nonradiative process (i.e. frequency constant). We have considered interaction with lattice phonons described by power dependence defined by exponent alpha, related to dimension of phonon space and effective phonon energy (h) over bar omega(eff). We found alpha approximate to 7.42 and (h) over bar omega(eff) = 315 cm(-1) for E-nr < 4000 cm(-1) and alpha approximate to 19.73, and (h) over bar omega(ef)f =1130 cm(-1) for E-nr. > 4000 cm(-1).