Morphological control and luminescence properties of lanthanide orthovanadate LnVO4 (Ln = La to Lu) nano-/microcrystals viahydrothermal process

Abstract

Lanthanide orthovanadate LnVO₄ (Ln = La to Lu) nano-/microcrystals with multiform crystal structures (monoclinic and tetragonal) and morphologies (separated nanoparticles, micropancake, microdoughnut and spherical aggregates) were successfully synthesized by a facile, effective, and environmentally friendly hydrothermal method. X-Ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, photoluminescence spectra, low-voltage cathodoluminescence, and kinetic decays were used to characterize the samples. The experimental results indicated that the use of the organic additive trisodium citrate (Cit³⁻) has an obvious impact on the morphologies of the products. The possible formation mechanisms for LnVO₄ nano-/microcrystals with diverse well-defined morphologies have been presented in detail. Additionally, we systematically investigate the luminescent properties of the LuVO₄:Ln³⁺ (Ln = Eu, Sm and Dy). Due to an efficient energy transfer from vanadate groups to the dopants, LuVO₄:Ln³⁺ (Ln = Eu, Sm and Dy) phosphors showed the strong characteristic emission of Ln³⁺ under ultraviolet excitation and low-voltage electron beam excitation. Furthermore, the PL emission color of LuVO₄:Ln³⁺ (Ln = Eu, Sm and Dy) phosphors can be tuned from blue to red, orange-red, and green easily by partial replacement VO₄³⁻ with PO₄³⁻ and changing the doping concentrations (x) of Ln³⁺.