Yolk–shell structured Gd2O3:Eu3+ phosphor prepared by spray pyrolysis: the effect of preparation conditions on microstructure and luminescence properties

Abstract

Gd₂O₃:Eu³⁺ yolk–shell phosphor powders with high photoluminescence intensity were prepared by spray pyrolysis. Preparation temperature and spray solution concentration were varied to find the optimum process conditions for preparation of Gd₂O₃:Eu³⁺ with yolk–shell structure. The formation mechanism of yolk–shell Gd₂O₃:Eu³⁺ was systematically investigated by observing the microstructures of particles produced under various preparation conditions. The morphological structure of Gd₂O₃:Eu³⁺ powders was clearly dependent on reactor temperature and on the precursor solution concentration. Eventually, pure yolk–shell structured Gd₂O₃:Eu³⁺ powders were obtained for a reaction temperature of 1000 °C and concentration of the spray solution below 0.2 M. Also, the yolk–shell structure formed showed high thermal stability, making it possible to maintain the original spherical yolk–shell structure through calcination at high temperatures. As a result, highly crystalline Gd₂O₃:Eu³⁺ phosphor powders having yolk–shell structure and an agglomeration-free spherical shape were successfully synthesized by spray pyrolysis. These phosphor powders were shown to have good photoluminescence characteristics.