On the efficient luminescence of β-Na(La1−xPrx)F4

This work describes the synthesis and the optical properties of β-NaLaF4 and β-NaLaF4 doped by Pr3+ as a function of the Pr3+ concentration. It is demonstrated that the emission spectrum is a strong function of the Pr3+ concentration and that the external PL efficiency increases with increasing Pr3+ doping level. An energy flow model involving cross-relaxation processes is given to explain this finding. The overall internal quantum efficiency is derived from decay time measurements and found to be 140% for low doping concentrations. Concentration quenching for emission from the 1S0 level is suppressed for concentrations up to 20% of Pr3+ giving rise to strong absorption and highly efficient line emission around 406 nm.