The Temperature Dependence of Rare‐Earth Activated Garnet Phosphors: II . A Comparative Study of Ce3+, Eu3+, Tb3+, and Gd3+ in

Abstract

Relative cathodoluminescence quantum intensity measurements made on crystals containing a series of concentrations of each of the ions Ce3+, Eu3+, Tb3+, and Gd3+ are reported as a function of temperature. For the first three of these activator ions the CL intensity increases with temperature, although the efficiency of Eu3+ luminescence rises much more steeply at low temperatures than Ce3+ and Tb3+. The temperature dependence of Gd3+ is very different, the luminescence intensity quenching rapidly above 120°K. The experimental results are rationalized in terms of proposed differences in the form of the impurity potential for each of these ions. Previously detected lattice defect levels are now assigned as hole trapping centers. Ce3+ and Tb3+ form competitive hole trapping centers. Eu3+, however, is found to be a stable electron‐attractive center. The potential for Gd3+ is predicted to be weak and this center forms no stable bound state. It is possible that long‐range energy transfer from the lattice defect level plays some role in Gd3+ excitation.