Crystallization of Gd2O3 nanoparticles: evolution of the microstructure via electron-beam manipulation

Abstract

NaGdF₄ is one of the most commonly employed phosphor host matrices for lanthanide doping and is one of the most efficient infrared-to-visible up-conversion fluorescent host materials. Although the structure, morphology and luminescence properties of NaREF₄ have been sufficiently investigated, there are very few reported instances of introducing localized order/crystallinity by electron-beam (e-beam) irradiation. In this work, we studied the phase transformation of Gd₂O₃ from an amorphous to crystalline form via manipulation by e-beam irradiation. The amorphous Gd₂O₃ occurs as an impurity in the cubic-NaGdF₄ nanoparticles (NPs). The structural evolutions, including the transformation from amorphous to crystalline, the recrystallization process and the formation of the graphene@NP core–shell structure, are discussed in detail. We also propose an evolution scheme, in which the e-beam manipulation of the organic-containing NPs induces a subtle structural transformation, depending in principle on the microenvironment of the NPs.