Tunable emission of Li 4 SrCaSi 2 O 4- y N 2 y / 3 :Eu 2+ phosphors based on anion substitution induction for WLEDs and optical thermometry.

Polychromatic emission can be achieved by controlling the distribution of the rare earth activator in multi-cation lattices, which can be used in the fields of white light LED and fluorescence temperature sensing. However, it is still a challenge to control their distribution and location of the target site in a given host material because the distribution of the rare earth activator is uncertain. In this paper, we have chosen Li 4 SrCa(SiO 4 ) 2 as the multi-cation site host and induced the distribution of Eu 2+ ions between different cation sites through anion substitution, for the first time, to regulate the luminescence characteristics of a series of Li 4 SrCaSi 2 O 8- y N 2 y /3 :Eu 2+ phosphors. In Li 4 SrCa(SiO 4 ) 2 :Eu 2+ phosphors, the substitution of O 2- by N 3- triggered a distinct ordered to disordered structure transition of the SiO 4 tetrahedron and induced the remote distribution of the Eu 2+ activator, which was verified through the analysis of the XRD, EPR, FT-IR and fluorescence spectra. Due to the location of Eu 2+ ions in different cation sites (Eu 2+ Sr and Eu 2+ Ca ), two distinguishable emission peaks with tunable color emissions and different responses to temperature were realized. The white LED that utilized blue-orange-emitting Li 4 SrCaSi 2 O 4 N 8/3 :Eu 2+ and green-emitting BaSi 2 O 2 N 2 :Eu 2+ (500 nm) displayed an outstanding color rendering index ( R a ) of 85.1. Based on the fluorescence intensity ratio (FIR) technique, an optical temperature measurement mechanism was hypothesized and studied in the temperature range of 293-473 K. The highest S a of the material was 0.086 K -1 , and S r was 1.76% K -1 based on the FIR detection technology, revealing obviously better than most inorganic optical temperature-measuring materials reported before. Our work indicates that Li 4 SrCaSi 2 O 8-2 y N 4 y /3 :Eu 2+ is a promising material for application in White LEDs and optical thermometers.