Luminescence and structural analysis of Ce3+ and Er3+ doped and Ce3+–Er3+ codoped Ca3Sc2Si3O12 garnets: influence of the doping concentration in the energy transfer processes

Abstract

We present research on Ca₃Sc₂Si₃O₁₂ garnets doped with Ce³⁺ and Er³⁺ ions that were synthesized by the freeze-drying precursor method. The structural characterization was performed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) images of the calcined material were studied. Nanocrystals of Ca₃Sc₂Si₃O₁₂ were obtained by calcining the precursor at 1200 °C for 4 h with a mean size of about 100 nm. The luminescence features of Ce³⁺ and Er³⁺ doped samples indicated that these ions are effectively incorporated into the crystalline phase. In addition, codoping with Ce³⁺–Er³⁺ ions results in energy transfer processes from Ce³⁺ to Er³⁺ ions which led to the enhancement of near-infrared luminescence at 1.5 μm. The efficiency of this non-radiative energy transfer process has been studied by means of excited state dynamics as a function of the doping concentration. From these results we have found that near-infrared Er³⁺ luminescence efficiency under VIS Ce³⁺ excitation is at maximal for 1Ce³⁺–1Er³⁺ codoped Ca₃Sc₂Si₃O₁₂ garnets (in mol%). Luminescence quenching at higher Er³⁺ ion concentrations is observed.