Synthesis And Optical Properties Of Vanadate Materials

In the vanadate materials,electrons transitions from the ground state to the excited state after absorbing the energy of the light,and then returns from the excited state to the ground state,causing the phenomenon of optical absorption and fluorescence emission.So vanadates can usually be used as a self-activated phosphor.When the sample particles are small enough,electrons and holes can easily migrate from the inside to the particle surface.Assuming that electrons and holes cannot be recombined,they will accumulate on the surface of the material.Consequently,the vanadate material will have a photocatalytic function.In this paper,vanadate self-activated luminescent materials and vanadate photocatalytic materials were prepared by various methods.In the study of Na1+xMg2-xV3-xMoxO10,Sr6-6xBa6xV2011 and CsV3O8 materials,the effect of cation doping on their light emission or photocatalytic performance was discussed,and the mechanisms were explored and explained.The main procedures are as follows:1.Na1+xMg2-xV3-xMoxO10(x=0-0.3)phosphor was prepared by solid-phase sintering.After the doping of materials,the luminous properties were significantly changed,the red-shift phenomenon occured in the excitation spectrum and the emission spectrum.In addition,the fluorescence lifetime was doubled,and the quantum efficiency and heat resistance are significantly improved.The influence of substitutions of(Mo6+→V5+)and(Na+→Mg2+)on the luminescence performance was studied by structural refinement.It was found that doped ions cause distortion of VO4 and the increase of interaction force between ions.The energy gap is reduced from 3.22eV to 2.95eV because the hybridization of V-3d/Mo-4d conduction band and defects in the band gap,which was more conducive to energy absorption and improves the optical performance of the sample.2.Sr6-6xBa6xV2O11(x=0-0.5)phosphor was prepared by the sol-gel method.After doping the material,the luminescence performance changed significantly,and the Stokes shift decreased.The spectrum showed a blue shift phenomenon,and the luminous efficiency was improved nearly doubled.The fluorescence lifetime was also significantly extended.By studying the influence of substitutions of(Ba2+→Sr2+)on the luminescence properties,it was found that the unit cell parameters increase with the increase of Ba2+,and the expansion of the lattice causes the V-O configuration and symmetry of the VO4 emission center to change.At the same time,the interaction between VO4,Ba2+ and Sr2+ is increased,and the optical properties of the sample are improved.3.CsV3O8 photocatalyst was prepared by hydrothermal method.It was found that the sample consisted of microwell plates with length and width of 1μm and 3 μm,the specific surface area was 75m2/g,and the pore size of the sample was 3 nm.Semiconductor materials have significant absorption at wavelengths within 570nm.According to the photocatalytic test,CsV3O8 semiconductor can degrade 96%rhodamine B solution within 3 hours.The effect of Cs+doping into the V2O5 layered structure on the photocatalytic effect was studied by structural refinement.It was found that the introduction of Cs+distorted the co-edge VO6,and the Cs-6s and O-2p orbitals hybridized and formed a valence band with a gap of 2.175 eV.The electronic transition method was indirect allowable transition.Part of V5+were affected by changes of the surrounding environment and becomes V4+(V5+:V4+=7:3).At the same time,the lattice changes caused defects O2ds-and Ods-on the surface,which enhanced the photocatalytic performance of the material.