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

Abstract

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 °C to 1460 °C, 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 °C and their properties are studied in detail. The luminescence of Mg₂Al₄Si₅O₁₈:0.005Cr³⁺ decreases with the increasing temperature, and about 56% is maintained at about 150 °C 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.