Enhanced photoluminescence and ultrahigh temperature sensitivity from NaF flux assisted CaTiO3: Pr3+ red emitting phosphor

Abstract

The Pr3+ doped CaTiO3 red emitting phosphor with enhanced PL and ultrahigh temperature sensing was prepared via NaF flux assisted solid-state reaction. All samples had the orthorhombic perovskite phase and no impurity was found. The typical sample mainly had sphere-like morphology with particle size of ∼670 nm. The optical bandgap values were ∼3.62–3.63eV. The Pr3+ quenching content was 0.6 mol% and the ET mechanism for quenching was the d-d interaction with the critical distance of 26.09 Å. A certain amount of NaF flux could enhance red emission attributed to 1D2→3H4 transition owing to improving the crystallinity of phosphors and reducing point defects near Pr3+ through the substitution of O2− by F− and Ca2+ by Na+. The energy storage trap (oxygen vacancy) near IVCT state played the key role for trapping electrons, accounting for the LAG emission and the average depth of trap was 0.39 eV. The CIE chromaticity coordinates were very close to that of the ideal red light and the CP was as high as 99.98%. The maximal Sa and Sr was as high as ∼0.015 K-1 and∼ 5.2% K−1, respectively. The thermal induced relaxation between the 3Pj levels and 1D2 level through the IVCT state was supposed to account for the excellent optical temperature sensing. Our work may provide a useful inspiration for developing ultrahigh sensitive optical temperature sensors.