Photoluminescence and photometric studies of low temperature prepared red emitting MgAl2O4:Cr3+ nanophosphors for solid state displays

Abstract

MgAl2O4:Cr3+ (0.01–0.11 mol) doped nanocrystalline powders were prepared by a combustion method at low temperature. The Scherer's method was used to estimate crystallite size and values were found to be in the range 20–30 nm and the same was confirmed by transmission electron microscopy (TEM) images. The energy band gap of the prepared samples was estimated from diffusion reflection spectra (DRS) and found to be 3.7–4.5 eV. The characteristic emission peaks recorded at 17123.3 cm−1 and 14727.5 cm−1 were attributed to the transitions 4T2→4A2 and 2E→4A2 respectively upon 357 nm excitation. The emission intensity increases up to 5 mol % Cr3+ particles and then decreases, which may be due to concentration quenching. The CIE (Commission International de I'E' clairage) chromaticity co-ordinates were calculated from emission spectra. They were close to the NTSC (National television standard committee) standard value of red emission. The average correlated color temperature (CCT) was found to be 2109 K. Therefore, the MgAl2O4:Cr3+ phosphor is useful for laser and solid state display applications. Keywords: MgAl2O4:Cr3+, Nanophosphor, Diffused reflectance, Photoluminescence, Racah parameters