Study on the cerium oxidation state in a Lu0.8Sc0.2BO3host

Abstract

Lu_0.8Sc_0.2BO₃:Ce powders doped with different forms of cerium [CeF₃, CeO₂ or Ce(NO₃)₃] were synthesized by solid-state methods under different conditions (carbon powders, nitrogen or air) and studied by a combination of X-ray excited luminescence spectra, optical diffuse reflectance spectra, fluorescence decay curves and X-ray absorption near edge spectroscopy. The optical diffuse reflectance spectra and fluorescence decay curves confirmed the different Ce³⁺/Ce⁴⁺ ratios in the samples of interest. Based on the Ce L_III-edge XANES spectra, we finally concluded that the differences in the scintillation intensities of the samples of interest originate from the varied Ce³⁺/Ce⁴⁺ ratios, which explains why the sample doped with CeF₃ and synthesized under carbon powder conditions shows an optimal scintillation emission. The specific Ce³⁺/Ce⁴⁺ ratio was also qualitatively determined by fitting the Ce L_III-edge XANES spectra. More importantly, this study further demonstrates the effectiveness of using XANES spectroscopy to investigate the cerium oxidation state in cerium-doped scintillators.