Facile modulation the sensitivity of Eu²⁺/Eu³⁺-coactivated Li₂CaSiO₄ phosphors through adjusting spatial mode and...

Series of Eu²⁺/Eu³⁺-coactivated Li₂CaSiO₄ phosphors were prepared by solid-state reaction technique. All the samples emitted the unique emissions of Eu²⁺ and Eu³⁺ ions when excited by 395 nm, while the strongest emission intensity was received when x = 0.03. On the basis of theoretical discussion, it is evident that crossover relaxation should be responsible for the thermal quenching mechanism which was further proved by the unchanged lifetime at elevated temperature. Besides, through analyzing the inconsistent responses of the emission intensities of the Eu²⁺ and Eu³⁺ ions to the temperature, the optical thermometric properties of the designed phosphors were studied. By selecting different emissions of Eu³⁺ ions and combining with that of the Eu²⁺ ions, adjustable sensitivities were realized in the resultant phosphors. Furthermore, the sensitivities of the studied compound were also found to be greatly affected by the doping concentration. The maximum absolute and relative sensitivities of the synthesized compounds were 0.0025 K^-1 and 0.289% K^-1, respectively. These achieved results implied that the Eu²⁺/Eu³⁺-coactivated Li₂CaSiO₄ phosphors were promising candidates for optical thermometry. Additionally, this work also provided promising methods to modulate the sensitivities of the luminescent compounds by adjusting spatial mode and doping concentration.