Synthesis And Luminescent Properties Of Rare Earth Doped Potassium Calcium Borate

Borate has been widely used as the matrix in optics,communications,medical and ceramics due to their diverse structure types,wide transparency,high luminous efficiency and high optical damage threshold.Nowadays the research on borate luminescence materials is mainly concentrated on anhydrous rare earth borate prepared at the high temperature condition.In fact,hydrated rare earth borate also has luminous performance,especially its mild preparation condition.The shortcomings like material granularity at the high temperature,morphology difficult control and easy sintering can be overcome.Now a variety of alkali metal and alkaline earth metal hydrate borate have been synthesized,because of their low valence,larger radius,not easy hydrolysis.Therefore,they can be used as matrix materials and rare earth ions can be used as the luminous central ions.As may be great meaningful for the further development of borate luminescence materials,even for the value promotion of borate mineral.K2Ca[B4O5(OH)4]2·8H2O(KCB),a kind of alkali metal and alkaline earth metal compound borate crystal,can be applied to nonlinear optical materials,special glass,lubricant additives and other fields.At present,some researches are focused on its structure,nonlinear optical property and solubility.But,the related dynamics research of preparation for KCB crystal has not been reported,especially the research on KCB doped rare earth still blank.In this paper,the single crystal of KCB with larger size was prepared by water solution synthesis method and its performance and structure were researched.A series of borate luminescent materials KCB doped Ce3+,Nd3+,Sm3+and Eu3+ were synthesized with homemade KCB:Re3+ as raw materials.The luminescence performance and stability of glasses were researched.Through XRD,SEM,EDS,ICP,TG-DTA-DSC,IR,Raman,11B NMR,excitation spectra and emission spectra analysis etc,the influences of technological conditions and the luminescent characteristics of rare earth doping were investigated.Crystallization kinetics and thermal analysis kinetics were studied.The main research results are as follows:The first,single crystal KCB was prepared by water solution synthesis.The crystal structural analysis and the effects of technological conditions(pH,the total concentration of boron,reaction temperature and cooling rate)on materials structure and performance were investigated.The suitable technological conditions were:pH of reaction solution 9.35,the total boron concentration 2.52 mol·L-1,reaction temperature 35? and cooling rate 2?/d.Under the suitable condition,the prepared crystal KCB had a complete crystal shape and uniform size of about 4mmx2mm×1mm.The crystal yield was up to 77.2%or so.The second,the crystallization kinetics analysis of crystal KCB was investigated.The result shows the preparation process of KCB is controlled by crystal growth.The crystallization kinetics equation is confirmed as the following:High concentration range:lndx/dt =-7.68-lnc0-4.57ln c o-dc/dt= 4.63×10-3(c-11.32×10-3)5(n?5)Low concentration range:Indx/dt=-1.09-lnc0-2.22lnc or-dc/dt= 3.37×10-1(c-11.32×10-3)2(n?2)The third,the dehydration process and kinetics analysis of crystal KCB were investigated by TG,DTA and DSC.The apparent activation energy of different peak and related to the reaction rate equation were calculated respectively.The results are listed as follows:The first peak:da/dt=1.759×1019e 144240/RT(1-a)1.383 The second peak:da/dt=6.742×1015e-117610/RT(1-a)0.970The fourth,Raman and 11B NMR spectra of KCB solutions were researched.The spectra showed that borate ions:B(OH)4-,[B3O3(OH)4]-and[B4O5(OH)4]2-were found in the solutions.The fifth,a series of new rare earth hydrous borate KCB:Re3+ doped Ce3+,Nd3+,Sm3+,Eu3+were synthesized by water solution method.The materials belong to monoclinic system,with the crystal structure like KCB.They have neat shapes with particle size about 1 mm to 4 mm.Spectral analysis show that the crystals have different luminous performance with different rare earth ions.The sixth,the spectra of KCB:Re3+(Ce3+,Nd3+,Sm3+,Eu3+)crystals under 100?,500?and700?heat treatment,respectively,were investigated.At 100?,there were better luminous effect for the crystals doped Ce3+and Nd3+,while weaker at not heating,500?and 700 ?,respectively.And the luminous ability of crystals doped Sm3+ and Eu3+ increase with the increase of temperature.The seventh,with four homemade KCB:Re3+(Ce3+,Nd3+,Sm3+,Eu3+)crystals as raw materials,rare earth borate glasses were prepared.The study found that luminescence properties of rare earth ions in glass were similar with KCB:Re prepared.KCB:Sm,KCB:Ce and KCB:Eu glass all can emit red light under ultraviolet excitation.The UV light can be converted into the red-emitting light.KCB:Nd glass can transfer infrared light to visible light,expected to be as raw a material for the conversion luminescence glass.The eighth,the activation energies of rare earth glasses crystallization were obtained by DSC analysis.The stability of rare earth glasses was determined and the orders were:The first exothermic peak(735?750?):Ce glass>Nd glass>Sm glass>Eu glass;The second exothermic peak(975?1010?):Eu glass>Sm glass>Ce glass>Nd glass.