Molten Salt Synthesis And Luminescence Properties Of Niobate Materials

Luminescence materials play a vital role in modern life,rare earth luminescent material as an important part of luminescence material has been widely used in various fields of analysis of fluorescence detection,lighting system and medical imaging detection.Niobate functional material not only has excellent chemical and thermal stability,and also has good properties in electro-optical and nonlinear optics,which has become a very important luminescence host material. At present,it is common to use high temperature solid state reaction method to synthesize niobate powders,The advantage of this method is that the process is relatively simple,suitable for mass production,but its disadvantages are also obvious,for example: the reaction energy demand,long required reaction time,easy to reunite and often accompanied by impurities.In the experiment,we prepare niobate functional materials by molten salt method,We study and analyze the effect of different conditions on the powder crystal structure and microscopic morphology to determine the best process preparation conditions.We synthetic K2La0.95Y0.05Nb5O15 phosphors with the tetragonal tungsten bronze type structure by doping different rare earth ions in K2LaNb5O15 matrix,study on the effect of rare earth ions on the luminescence properties,analyze the energy transfer relationship between ions and matrix. The main contents are as follows:1.K2LaNb5O15 powders was successfully synthesized via Molten salt method by using Nb2O5,La2O3 and KCl as the raw materials.KCl is the source of potassium and molten salt.The crystal structure and microscopic morphology of K2LaNb5O15 powders at different conditions were characherized using the X-ray diffraction and scanning electron microscope.The results show that the best proportion of molten salt is KClactual/KCltheory=7.5:1,at this time the structure of the product is more uniform.With the continued increase in the amount of molten salt,the uniformity of product morphology table is poor,minority grain unusually grew up.The KCl melted at 770 ℃,K2LaNb5O15 began to crystallization,along with the increase of the crystalline of K2LaNb5O15 powders,crystal preferential growth along a crystal orientation,the powders are granulated.With the increase of calcination temperature, particle morphology gradually transition into stick.The best heat treatment temperature is 1000 ℃,at this time the K2LaNb5O15 crystallize completely,the morphology of powder is uniform stick.When the holding time is 2h and 3h,the morphology of the product is relatively uniform.The uniformity of the powder morphology variation with further extension of the holding time.Only using KCl as molten salt, the morphology of the product is more uniform and regular, with the increase of K2SO4 in molten salt, the morphology of product is not uniform.2.We synthetic K2LaNb5O15:Ln3+ phosphors with the tetragonal tungsten bronze type structure by doping different rare earth ions in K2LaNb5O15 matrix. The crystal structure and microscopic morphology of K2LaNb5O15 powders under different calcination temperature was characherized using the X-ray diffraction and scanning electron microscope.The Excitation spectrum and emission spectrum of K2LaNb5O15 and K2LaNb5O15:Ln3+ powders was characherized using fluorescence spectrometer.The results show that K2LaNb5O15 with the tetragonal tungsten bronze type structure has a strong luminescence characteristics.The excitation spectra of K2LaNb5O15:Ln3+ phosphor is composed of two parts,they are caused by The f-f transition of rare earth ions and NO6 charge transition,this shows that there is energy transfer from K2LaNb5O15 to rare earth ions.