Study On Shape-controlled Synthesis And Fluorescence Properties Of LaVO₄: Ln(Ln=Eu³⁺, Er³⁺)

As a new material, rare earth vanadates play an important role in many fields, such as thelight decomposition catalyst, polarizer in optical instruments and nano/micro fluoresce-ence materials. Recently, rare earth vanadates have been studied by many researchs focusingon how to control the reaction kinetic conditions which maybe effect the crystal growthprocess, summarizing the realationship between reaction conditions, crystal structure andproperties, and mastering with some special morphology. In this paper, a series of lanthanumvanadate with different morphologies have been preprared. The effects of experimentalconditions on the shape of crystals have been investigated new synthesis method of t-LaVO4has been provided by using azelaic acid template. The main work is as follows:1. Star-like LaVO4: Er3+particles have been synthesized by hydrothermal method. Theoptimal conditions to obtain star-like LaVO4: Er3+have been found with LaCl3·7H2O andNH4VO3as reactants, citric acid(CA) as template, the c(CA)/c[La3+(Er3+)]=2.5, the pH valueof14adjusted by NaOH, dropping Er(NO3)3solution to control c(La3+)∶c(Er3+)=17∶1, thereaction temperature of180℃for48h. There are3emission peaks in414nm,470nm and540～565nm. Purple light is from Er3+(2H9/2�'4I15/2, the emission peak center at414nm)transition, blue light is from the LaVO4as a matrix, luminescence center is located in470nm,green light is from Er3+(4S3/2�'4I15/2, between540～565nm) transition.2. Rod-like t-LaVO4: Eu3+particles with uniform morphology have been synthesized byhydrothermal method. The optimal conditions to obtain Rod-like t-LaVO4: Eu3+have beenfound with LaCl3·7H2O and NH4VO3as reactants, the pH value of12adjusted by NaOHsolution, dropping Eu(NO3)3solution to control c(La3+)∶c(Eu3+)=17∶1, Na2EDTA (Eth-ylenediaminetetraacetic acid disodium salt) as template, c(Na2EDTA)/c[La3+(Eu3+)]=1.15, thereaction temperature of180℃for36h. Rod-like t-LaVO4: Eu3+particles have3emissionpeaks in580~610、610~680、690~725nm which correspond to Eu3+5D0�'7FJ(J=1,2,4)transition. The strongest emission peak in610~680nm, center of peak in618nm is red bandemission. The high temperature properties of products were tested in the paper, the test resultsshow that: under the900℃, the phase of products is stable.3. t-LaVO4: Eu3+nanoparticles have been synthesized with a new template: azelaic acid.The optimal conditions to obtain LaVO4: Er3+nanoparticles have been found withLaCl3·7H2O and NH4VO3as reactants, c[La3+(Eu3+)]/c(azelaic acid)=1.15, azelaic acid astemplate, the pH value of12adjusted by NaOH solution, dropping Eu(NO3)3solution tocontrol c(La3+)∶c(Eu3+)=17∶1, the reaction temperature of180℃for48h. The optimal conditions to obtain t-LaVO4: Eu3+nanoparticles fluorescence spectra have3characteristicemission peaks, the strongest peak at610~680nm, the weakest peak at690~725nm,correspond to Eu3+5D0�'7FJ(J=2,4) transition.