Cerium Concentration and Temperature Dependence of the Luminescence of SrGa2 S 4 : Ce , Na , a Blue‐Emitting Material for Electroluminescent and High Current Density Cathodoluminescent Displays

Abstract

The cerium concentration and temperature dependence of the spectral distribution, quantum yield, and lifetime of the photoluminescence has been investigated in powders having the composition (x ⩽ 0.5). With increasing cerium concentration the emission shows a strong shift to longer wavelengths caused mainly by changes in the ligand field. Despite a relatively small Stokes shift , the emission shows a low concentration quenching up to x = 0.10. Because of the size differences between the , and ions, cerium ions possess various environments. Energy migration to defects is impeded by the transfer of the excitation energy to the ions having the lowest emitting states, whose emission exhibits reduced overlap with the absorption of other ions. As a result of the small Stokes shift, at low Ce concentration the luminescence is not affected by the thermal quenching up to 500 K. The low concentration quenching and the high thermal stability are favorable characteristics for use of this phosphor in electroluminescence and high current density CL screens.