Probing structural and luminescence properties of Ce3+ doped MgO nanocrystals via XAS, PL, and TL studies

Abstract

MgO:Ce and MgO:CeLi nanocrystals have been prepared using the solution combustion method and investigated for structural, electronic structure, photoluminescence, and thermoluminescence properties. X-ray diffraction (XRD) analysis revealed the single-phase formation of MgO:Ce amd MgO:CeLi compounds up to 0.1 mol% of Ce doping. The formation of CeO2 phase has been observed at 2 mol% Ce doping in MgO. Low energy shift in the Mg K-edge X-ray absorption near edge structure (XANES) spectra conveys favorable tetrahedral site occupancy of Mg2+ ions in MgO:Ce nanocrystals. The enhanced intensity of the O K-edge XANES feature, in MgO:Ce samples, reveals a more, p-projected, unoccupied density of states and significant hybridization of Ce 4f and O 2p states. Ce L3 edge XANES spectra confirmed the coexistence of Ce4+ and Ce3+ ions in the samples. Photoluminescence (PL) experiments, conducted with UV LED excitation at 275 nm and 310 nm, showed emissions in two regions; a blue region centered at 430 nm and a red region at 670 nm in pure MgO. Additionally, distinct emission bands corresponding to Ce 5d-4f transitions were observed and the Li co-doping could enhance the PL intensity. Thermoluminescence (TL) studies of the samples were conducted after being exposed to the different doses (100 Gy, 500 Gy, 1 kGy) of gamma radiation. The deconvolution of TL peaks has confirmed the presence of multiple traps. Kinetic parameters of TL glow peaks revealed re-trapping and closely spaced traps within the forbidden band gap. The stability and linear behavior of TL peaks demonstrated the excellent dosimetry characteristics of prepared MgO: CeLi nano phosphors.