Blue luminescence from ZnGa₂O₄: Effect of lattice distortion and particle size

Dependence of structural and luminescence properties of nano-crystalline ZnGa₂O₄ phosphors on the synthesis conditions such as concentration of precursor metal ions and nature of solvents were investigated in detail. Based on XRD and luminescence studies carried out on samples prepared with high and low concentrations of precursor metal ions in ethylene glycol medium, it is established that distortion of structural units along with defects/traps in the lattice, and not the particle size, is responsible for the observed blue shift in emission maxima with decrease in precursor concentrations. Unlike this, a red shift is observed when the synthesis is carried out under identical conditions in water medium. This has been explained based on difference in particle size distributions as confirmed by TEM studies.