Preparation of highly crystalline blue emitting MVO4:Tm3+ (M=Gd, Y) spherical nanoparticles: Effects of activator concentration and annealing temperature on luminescence, lifetime and quantum yield

Highly crystalline spherical nanoparticles of MVO4:Tm3+ (M=Gd, Y) having a size of 20-45 nm were prepared using ethylene glycol as both capping agent and reaction medium. X-ray diffraction study shows linear decrease in the unit cell volume with an increase in Tm3+ concentrations in MVO4 (M=Gd, Y; Tm3+=0, 2, 5, 7, 10, 15, 20, 40, 60, 80 and 100 at%), indicative of quantitative substitution of Gd3+/Y3+ lattice sites by Tm3+ ions in MVO4. Blue light emission at 475 nm is observed after excitation at 310 nm due to energy transfer from VO43− absorption band to Tm3+. Emission intensity and average decay lifetime increase with an increase in heat treatment from 500 to 900 °C. This has been attributed to an extent of reduction in non-radiative process arising from surface. The emission intensity of Tm3+ in GdVO4 host is higher than that in YVO4 and thus the former host is better. Quantum yield increases with increase in heat-treatment temperature. This material will be the alternative blue light emitter.