Low-temperature synthesis of YVO₄: Bi³⁺, Eu³⁺ nanoparticle phosphors using a methanol solution of trivalent cations

A homogeneous solution of Y³⁺, Bi³⁺, and Eu³⁺ in methanol was used for low-temperature (70°C) synthesis of YVO₄:Bi³⁺, Eu³⁺ nanoparticles. X-ray diffraction and fluorescence analyses revealed phase-pure tetragonal YVO₄:Bi³⁺, Eu³⁺. Transparent colloidal solutions were prepared having well-dispersed ∼8-nm YVO₄:Bi³⁺, Eu³⁺ nanoparticles. Increases in elemental Bi content at the constant Eu content increased the lattice spacing linearly. This reveals that Bi³⁺, which is larger than Y3+ and Eu³⁺, substitutionally incorporated in YVO₄:Eu³⁺. The absorption edges and photoluminescence excitation edges were red-shifted by doping Bi³⁺ in YVO₄:Eu³⁺, and red emission from Eu³⁺ was observed under near-ultraviolet excitation. These results indicate that Bi³⁺ and Eu³⁺ were successfully co-doped into the YVO₄ host crystal. Concentration quenching was not observed with increasing Bi-doping even until 6.5 at%, although the quenching of bulk YVO₄:Bi³⁺, Eu³⁺ prepared by solid-state reaction was observed with >3 at% in a previous report. This implies a better chemical homogeneity of Bi in the host crystal or a structural disorder which prevents the energy migration between Bi³⁺.