Broadening of the near-infrared emission band of the Mg2Al4Si5O18:Cr3+ phosphor for illumination emission applications

Near-infrared (NIR) emission materials have been widely used in food inspection, spectral analysis, and so on. The broader the emission band of NIR phosphors, the more the components will be detected, making the search for broadband NIR phosphors still under demand. Herein, a broadband NIR phosphor with a FWHM of 259 nm is obtained by adjusting the synthesis temperature, due to the intrinsic advantages of phase transition and microstructure diversity in the Mg2Al4Si5O18 compound. As the sintering temperature increases from 1400 degree celsius to 1460 degree celsius, the partial Mg2Al4Si5O18:Cr3+ sample is transformed from the low temperature phase to the high temperature phase with a broadening of the emission FWHM from 25 nm to 259 nm, which can be attributed to the longer Mg-O bond and the larger volume of the [MgO6] octahedron causing a weaker crystal field after the phase transition. A series of phosphors with different Cr3+ doping concentrations are synthesized at the optimum synthesis temperature of 1450 degree celsius and their properties are studied in detail. The luminescence of Mg2Al4Si5O18:0.005Cr(3+) decreases with the increasing temperature, and about 56% is maintained at about 150 degree celsius and the emission peak width still remains at 251 nm. NIR phosphor-converted LEDs (pc-LEDs) with an output power of 6.82 mW and a photoelectric efficiency of 3.82% are achieved. This work provides fresh insight into the exploration of novel Cr3+ ion-based broadband NIR materials for pc-LEDs.