Photoluminescence properties of CaLa(PO)SiOF:Ce/Tb/Mn phosphors for applications in white light-emitting diodes and optical thermometers.

A series of CaLa(PO)SiOF:Ce,Tb,Mn (CLPSF:Ce,Tb,Mn) phosphors were obtained by a conventional solid-state reaction method, and the luminescence properties excited by ultraviolet light were investigated in detail. The Ce-doped CLPSF samples show near-ultraviolet luminescence with the dominant peaks around 361 nm. Different Ce emission centers were identified from the emission spectra. When the Ce and Mn are codoped into the host, an energy transfer (ET) from Ce to Mn 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 Ce-Tb codoped CLPSF phosphors, the tunable emission was realized on the basis of the ET between Ce and Tb. To further obtain the white emissions with tunable correlated color temperature, the Ce-Tb-Mn 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 Ce and Mn emission intensities in the CLPSF:Ce,Mn 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:Ce,Tb and CLPSF:Ce,Tb,Mn phosphors exhibit relatively high thermally luminescent stability. The above discoveries indicate that the developed phosphors could have potential applications in LEDs and optical thermometer.