The influence of Cr3+ concentration on the structure and photoluminescence of MgAl2O4:0.1% Eu3+, x% Cr3+(0≤x≤0.15%)nanophosphor synthesized by sol-gel process

MgAl2O4 and 0.1% Eu3+, x% Cr3+ co-activated nano-phosphors were successfully prepared using the sol-gel method. The co-activator (Cr3+) mol% was varied at a range of 0≤x≤0.15%. All annealed samples consist of the pure cubic MgAl2O4 structure. Varying the Cr3+ concentration influenced the surface morphology of the nano-phosphor. The host, 0.1% Cr3+ and 0.1% Eu3+ activated nanophosphor emits at different wavelengths. The emission peak at 398 nm is attributed to the defect within the host. The emission peaks at 403, 565 and 694 nm are attributed to arise from the Cr3+ transitions from 4T1 → 4A, 4T2 → 4A 2 and 2E → 4A2, respectively. The emission peaks at 574 and 619 nm are respectively attributed to the 5D0 → 7F1 and 5D0 → 7F2 transitions in the Eu3+ ion. No evidence of energy transfer was observed. The emission colour could be turned by varying the co-activator concentration and excitation wavelength.