Tunable luminescence and efficient energy transfer investigation of a borosilicate phosphor KBSi2O6: Bi3+, Eu3+ with hypersensitive thermal quenching.

Energy transfer between Bi3+ and Eu3+ has undergone substantial research but Bi3+ and Eu3+ co-doped luminescent materials with high energy transfer efficiency for temperature sensing are rarely investigated until now. Herein, Eu3+ and Bi3+ co-doped KBSi2O6 phosphors were successfully synthesized by solid-state reaction method. The phase purity structure as well as the element distribution were carefully investigated through X-ray diffraction structural refinement and energy dispersive spectrometer analysis. The characteristic luminescence property and luminescence kinetics of KBSi2O6: Bi3+, Eu3+ were investigated. By the large spectra overlap between the emission spectrum of Bi3+ and excitation spectrum of Eu3+, the energy transfer from Bi3+ to Eu3+ can be inferred. The corresponding decrease of the emission intensity and decay time of Bi3+ in KBSi2O6: Bi3+, Eu3+ provided direct evidence for the effective energy transfer from Bi3+ to Eu3+. The interaction and energy transfer mechanism between Bi3+ and Eu3+ ions were also studied. By increasing the Eu3+ concentration in KBSi2O6: Bi3+, Eu3+, the color-tunable emission from blue to red can be realized. KBSi2O6: Bi3+, Eu3+ shows hypersensitive thermal quenching behavior and the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) are determined to be 1.87 %K-1 and 2.895 %K-1, respectively. All of the above results imply that KBSi2O6: Bi3+, Eu3+ phosphor can be a color-tunable phosphor for optical temperature sensing.