Effect of Cr3+ on the microstructure and photoluminescence of MgAl2O4 transparent ceramic

MgAl2O4: Cr3+ transparent ceramics were synthesized by hot pressing (HP) technique, LiF and Y2O3 as sinter aids. The effect of Cr3+ on the densification, structure, and luminescence of MgAl2O4 transparent ceramic was studied. The phase structure, micromorphology, and photoluminescence were analyzed by using an x-ray diffractometer, field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, excitation, emission spectra, quantum yield, and decay curves. The results showed that the relative density of the ceramic increased from 99% to 99.45% with the increase of Cr3+ content, meanwhile, more Al3+ sites were occupied by Cr3+ ions, and the Y3+ ion in the sinter aids gathered at the grain boundary, which caused the decrease of the optical transmittance. The relative density of the ceramic with 0.12 mol% Cr3+ is 99.17%, and its optical transmittance was above 67% in the range of 700-6000 nm, and the highest was 74% at 1440 nm. The characteristic R-line centered at 686 nm, and the N-line centered at 700 nm of Cr3+ ions were observed. The quantum yield of the R-line was improved with the increase of x and reached 35.8% at Cr3+ content of 0.37%. Additionally, with the increase of Cr3+ content, the Dq/B value increased from 3.19 to 3.31.