Photoluminescence properties of Ca9La(PO4)5SiO4F2:Ce3+/Tb3+/Mn2+ phosphors for applications in white light-emitting diodes and optical thermometers

Abstract

A series of Ca9La(PO4)5SiO4F2:Ce3+,Tb3+,Mn2+ (CLPSF:Ce3+,Tb3+,Mn2+) phosphors were obtained by a conventional solid-state reaction method, and the luminescence properties excited by ultraviolet light were investigated in detail. The Ce3+-doped CLPSF samples show near-ultraviolet luminescence with the dominant peaks around 361nm. Different Ce3+ emission centers were identified from the emission spectra. When the Ce3+ and Mn2+ are codoped into the host, an energy transfer (ET) from Ce3+ to Mn2+ was found, owing to which the visible emitting-light-color has been tuned from blue to light brown. The corresponding ET mechanism was studied by employing Dexter's theory. In the Ce3+-Tb3+ codoped CLPSF phosphors, the tunable emission was realized on the basis of the ET between Ce3+ and Tb3+. To further obtain the white emissions with tunable correlated color temperature, the Ce3+-Tb3+-Mn2+ tridoped CLPSF samples were designed, and the ET relationship in these phosphors were discussed. By studying the thermally luminescent properties, it was found that the Ce3+ and Mn2+ emission intensities in the CLPSF:Ce3+,Mn2+ samples showed different decrease rates with increasing temperature. The fluorescence intensity ratio (FIR) technique was used to investigate the temperature-sensing performance. On the other hand, the CLPSF:Ce3+,Tb3+ and CLPSF:Ce3+,Tb3+,Mn2+ phosphors exhibit relatively high thermally luminescent stability. The above discoveries indicate that the developed phosphors could have potential applications in LEDs and optical thermometer.