LaF3 and LaF3:Ln3+ (Ln = Eu, Tb) hierarchical microstructures: synthesis, characterization and photoluminescence

Abstract

Without any templates or surfactants, large-scale 3D persimmon-shaped hierarchical LaF₃ and LaF₃:Ln³⁺ (Ln = Eu, Tb) have been synthesized via a simple hydrothermal route using organic tetrafluroborate complexes N(C₄H₉)₄BF₄ as the fluoride source. The phase and morphology of the products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The SEM and TEM results indicate the 3D persimmon-shaped hierarchical microstructures are constructed by numerous nanodisks with mean thickness of 50 nm. It is found that several factors, including the fluoride sources, molar ratio of reagents and the reaction time, play crucial roles in the formation of the multilayer stacked structures. Detailed studies indicate that the layer-by-layer self-assembly of nanodisks is responsible for the formation of 3D hierarchical structures. The possible mechanism of the crystal growth and assembled procedure are also proposed. Furthermore, the photoluminescent properties of LaF₃:Ln³⁺ (Ln = Eu, Tb) are studied, which exhibit orange-red (Eu³⁺:⁵D₀–⁷F_1,2,3,4) and green (Tb³⁺, ⁵D₄–⁷F_3,4,5,6) emission, respectively.