Hydrothermal Synthesis and Microstructural, Optical Properties Characterization of $YVO_4$ Phosphor Powder

The phonon energy of $YVO_4$ crystal is lower than other usual compounds of salt. So it is suitable as host material for down-conversion materials. Hydrothermal method was adopted to synthesize $YVO_4$ phosphor powder with the use of yttrium oxide and sodium vanadate as raw material. The change in the relative integral intensity of the (200) and (112) diffraction peaks indicates that macroscopic stress in the lattice obviously changes with the elevated hydrothermal reaction temperature. The $YVO_4$ phosphor powder synthesized involves a certain agglomeration of small particles. The phonon vibration in the $YVO_4$ originates mainly from the internal vibrations in the vanadium-oxygen tetrahedron, in addition to the Y-O and O-H vibrations. Due to a low phonon energy of only $2.8188 × 10^{-21} J$, $YVO_4$ helps to improve the down-conversion efficiency of rare-earth ions. A bandgap value of approximately 3.8 eV for the synthesized $YVO_4$ powders leads to good absorption properties in the ultraviolet region. Upon excitation by the 320 nm ultraviolet photon, the intrinsic emission of $YVO_4$ powders is annihilated, and a broadband emission of $VO_4^{3-}$ near 450 nm is observed at room temperature. The $YVO_4$ phosphor powder synthesized at 180C exhibits the maximum photoluminescence intensity because of its excellent crystallization.