A statistical model of thermal ionization of excited Ce ions in YAG.

A statistical model based on the condition of thermal and diffusive equilibrium between the conduction electrons and the electrons in the excited 5d 1 level of Ce3+ is presented. Using this model, we find the probability for an excited Ce3+ ion to be thermally ionized leading to an electron in the conduction band. The density of conduction electrons is then calculated over a wide range of temperatures and excitation densities. The observed quenching of emission at high temperature in Ce-doped YAG with low Ce concentrations is also investigated within this model. It is shown that the experimentally-observed nonradiative losses in this phosphor can be reasonably simulated assuming losses occur via nonradiative decay from the conduction band to the Ce3+ ground state. • We present a model of thermal ionization in YAG:Ce leading to conduction electrons. • The density of conduction electrons in YAG:Ce is calculated. • Conduction electron trapping by Ce4+ explains losses in YAG:Ce at high temperatures. • Discrepancy between activation energy and ionization energy is explained. [ABSTRACT FROM AUTHOR]