Dual luminescence optimization of Ho3+/Yb3+/Eu3+-doped Gd2O3 phosphor prepared by spray pyrolysis for anti-counterfeiting application

Abstract

Ho3+/Yb3+/Eu3+-doped Gd2O3 spherical particles with upconversion (UC) and down-conversion (DC) emission were synthesized by spray pyrolysis. The resulting phosphor showed intense DC red and UC green emissions. The Eu3+, Ho3+ and Yb3+ contents were optimized to simultaneously achieve the highest UC and DC emission. Resultantly, the optimal Eu3+, Ho3+ and Yb3+ doping concentrations were found as 0.2%, 3.0% and 0.2%, respectively. The green UC emission resulted from a typical two-photon process, and the UC and DC emission intensity showed a linear relationship with crystallite size. The microstructure of Gd2O3:Ho3+/Yb3+/Eu3+ was controlled by introducing organic additives into the spray solution. The use of organic additives made it possible to improve crystallinity having a dense morphology, which led to largely enhance the DC and UC intensity. The prepared Gd2O3:Ho3+/Yb3+/Eu3+ spherical particles showed excellent dual luminescence suitable as anti-counterfeiting security materials.