Hydrothermal Synthesis/Solvent Thermal Synthesis And Luminescence Property Study Of Rare Earth Europium Ions Doped Cd₂V₂O₇ Microcrystals

Because of the variation structures,vanadates have attracted more and more attentions as luminescent materials in recent years,which can be used as solar cell light conversion materials to improve the solar energy utilization.In this paper,four different morphologies of cadmium vanadate(Cd₂V₂O₇:Eu³⁺)microcrystalline materials have been synthesized by hydrothermal/solvothermal method as raw materials of NaVO₃ and Cd?NO₃?₂·4H₂O.The products are characterized by means of X-ray powder diffraction,scanning electron microscope and fluorescence spectrometer.With the variation of the pH values,reaction time,reaction temperature and other conditions,a systematic study has been carried out to prepare Cd₂V₂O₇:Eu³⁺light-conversion materials with controllable morphology and high luminescence intensity.The main achievements are as follows:1.Hydrothermal synthesis of Cd₂V₂O₇:Eu³⁺microcrystals with different morphologiesWe have studied the effect of pH value,the amount of surfactant,reaction temperature,and reaction time on the Cd₂V₂O₇:Eu³⁺microcrystals.The optimum conditions have been determined for the synthesis of Cd₂V₂O₇:Eu³⁺microcrystals with four morphologies.The obtained products exhibit a strong emission peak in the range of 612⁶16 nm under the excitation number of 398 nm.?1?Hydrothermal synthesis of spherical Cd₂V₂O₇:Eu³⁺microcrystalsThe optimum conditions for the synthesis of spherical Cd₂V₂O₇:Eu³⁺microcrystals with a diameter of 2.6?m are as follows:the n?EDTA?/n(Cd²⁺)mole ratio of is 1:4,the reaction temperature of 180?a nd the reaction time of 12 h.?2?Ethanol-solvothermal synthesis of flake-flower spherical Cd₂V₂O₇:Eu³⁺microcrystalsThe optimum reaction conditions for flake-flower spherical Cd₂V₂O₇:Eu³⁺microcrystals in the diameter of 2.2².5?m are as follows:the pH value of 9,the ethanol/water volume ratio of 2:1,the n?SDS?/n(Cd²⁺)mole ratio of 2:1,the reaction temperature of 180?and the reaction time of 12 h.?3?Hydrothermal synthesis of hollow spherical Cd₂V₂O₇:Eu³⁺microcrystalsThe optimum reaction conditions for hollow spherical Cd₂V₂O₇:Eu³⁺microcrystals in the diameter of 4.3?m are as follows:the pH value of 8,the n?CTAB?/n?PVP?mole ratio of 2:1,the reaction temperature is 180?and the reaction time is 12 h.?4?Hydrothermal synthesis of rod-shaped Cd₂V₂O₇:Eu³⁺microcrystalsThe optimum reaction conditions for rod-shaped Cd₂V₂O₇:Eu³⁺microcrystals with aspect ratio of 12 are as follows:the pH value of 8,the NH₄Cl amount of 10mL,the reaction temperature of 180?and the reaction time is 12 h.2.Synergistic effect of CTAB and PVPDue to the action of hetero adsorption,the amount of CTAB regulates the morphology of the products.By adjusting the amount of PVP,the longitudinal growth of the products can be controlled to form a two-dimensional rod-shaped structure.The controllable morphology of the product can be achieved by the use of both CTAB and PVP and the adjustment of its proportion.3.The role of EDTA in hydrothermal synthesis?1?Controlling the concentration of free Cd²⁺EDTA is a common chelating agent which can form a stable complex with Cd²⁺to form Cd^2+_<sub>EDTA in solution.With the decomposition of Cd2+_<sub></sup>EDTA,Cd2+was released slowly to prevent the too higher concentration of local Cd2+,and Cd2+can combine with free vanadate to form Cd₂V₂O₇.?2?Template agentThe particle crystals can aggregate together to form spherical Cd₂V₂O₇microcrystals,when the pH value of the precursor solution is 9 and the n?EDTA?/n(Cd2+)mole ratio is 1:4.4.In comparison to Cd₂V₂O₇:Eu3+microcrystals with four morphologies,the fluorescence intensity is in proper order:spherical>hollow spherical>rod>flower-shaped.</sup>