On the efficient luminescence of beta-Na(La1-xPrx)F-4

Abstract

This work describes the synthesis and the optical properties of beta-NaLaF4 and beta-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 S-1(0) level is suppressed for concentrations up to 20% of Pr3+ giving rise to strong absorption and highly efficient line emission around 406 nm. (C) 2013 Elsevier B.V. All rights reserved.