Low-temperature thermoluminescence in CaGa2S4:Eu

In the last years many insulating and semiconducting materials activated with rare-earth elements were found to exhibit phosphorescence and thermoluminescence properties, and are attracting increasing interest due to the variety of application of long-lasting phosphors. In this work we studied the phosphorescence decay and thermoluminescence properties of CaGa₂S₄:Eu²⁺ as a function of temperature in the 9-325 K range. The comparison between spectra recorded as a function of time delay from the excitation pulse at different temperatures indicates that long-lasting emissions peaked at about 2.2 eV occurs at Eu²⁺ sites. Thermoluminescence glow curve is characterized by five components at 69, 98, 145, 185 and 244 K. Experimental data are discussed in the framework of generalized order of kinetic model and allow to estimate the activation energies of trapping defects. The origin of glow components at 69, 98, 145 and 244 K is correlated to trapping defects induced by Eu²⁺ doping, while the component at 185 K is attributed to a continuous distribution of defects.