Combining complexing agent and solvothermal reaction for the morphology controlled synthesis of (Y,Eu)PO4 crystals with size-dependent photoluminescence

Abstract

Hexagonally structured YPO₄ (h-YPO₄) micro/nanocrystals with the multiform morphologies of quasi-equiaxed microprisms, quasi-ellipsoidal nanoparticles, and sphere-like nanoparticles, have been successfully synthesized via a facile solvothermal reaction in the co-presence of appropriate amounts of ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA) or citric acid (CA). A series of precisely controlled experiments indicated that EG can significantly amplify the abilities of EDTA and CA in modifying the growth regimes of YPO₄. Detailed characterizations of the products were implemented by the combined techniques of XRD, FE-SEM, TEM, LPSA (laser particle size analysis), FTIR, and optical spectroscopy, and the mechanisms of the morphology/phase evolution of the YPO₄ crystals were investigated via altering the EDTA/Y and CA/Y molar ratios, and the EG content. The particle size-dependent luminescence properties of h-(Y_0.95Eu_0.05)PO₄, including the luminescence intensity, fluorescence lifetime, asymmetry factor of luminescence ((⁵D₀ → ⁷F₂)/(⁵D₀ → ⁷F₁) intensity ratio), and CIE chromaticity coordinates, were also investigated in detail.