Inorganic Salt Isolation Method For The Synthesis Of Nano YAG:Ce³⁺ Phosphor

Cerium-doped yttrium aluminum garnet(Y₃Al₅O₁₂:Ce³⁺,referred to as YAG:Ce³⁺)is one of the indispensable phosphor components in white LEDs.The efficacy and photochromic properties of white LEDs are closely related to the performance of YAG:Ce³⁺.Particle size and dispersibility are key performance indicators of YAG phosphors.Reducing particles to nanometer size can significantly improve the uniformity of light output of white LEDs and eliminate the light scattering loss caused by phosphor particles.However,the preparation of highly dispersed nano-YAG:Ce³⁺phosphors has been a technical bottleneck in the art,because it is difficult to avoid sintering of nanoparticles at high temperatures.In this paper,the water-soluble inorganic salt was introduced into the high-temperature isolation phase,and the agglomeration and sintering of the nanoparticles during high-temperature synthesis of YAG:Ce³⁺were successfully solved.YAG:Ce³⁺phosphor particles with a particle size of only 20 nm were prepared,and the particles were dispersed and the crystallinity was good.The basic process of the water-soluble salt isolation method used herein is to disperse and mix the YAG precursor nanoparticles and the potassium sulfate salt particles in an organic solvent,and to synthesize the YAG:Ce³⁺phosphor at a high temperature after drying.During the high temperature calcination process,the potassium sulfate salt particles always play a role of isolation,avoiding the agglomeration and sintering of the YAG nanoparticles.The preparation of the precursor and its dispersion mixing with the salt particles are the key links,which affect the particle size and phase purity of the YAG phosphor.In this paper,the preparation of YAG precursors with sodium carbonate as precipitant was studied.Three methods of forward precipitation,reverse precipitation and double-drop co-precipitation were studied.The effects of pH on the phase and particle morphology of YAG were investigated.Studies have shown that pH not only affects the product phase,but also affects the uniformity of the particles;when the pH is too low,the ruthenium cannot be completely precipitated,and the YAP heterophase remains in the product.When the pH is too high,the precipitation of aluminum dissolves,and the precipitate in the precipitate is more The method of double-drip co-precipitation keeps the size of the precursor and YAG nanoparticles relatively uniform when the pH of the precipitation process is maintained at 7.In order to ensure the pH stability during the precipitation process,the precursor preparation by urea coprecipitation method was tried,and the mixing mode,mixing ratio and solvent of the precursor and potassium sulfate were studied.The particle size and morphology of the YAG phosphor were studied.influences.The study found that when the precipitation temperature is 85°C,the precipitation time is 40 minutes,and the surfactant is PEG2000,the uniformly dispersed YAG precursor particles can be obtained;the smaller the salt particles,the more dispersed the prepared YAG particles;the higher the salt ratio The better the dispersibility of YAG particles,the smaller the particle size.When the salt ratio exceeds 8 times,the change is not obvious;the mixing effect in xylene and ethanol is good,and the dispersibility of YAG nanoparticles after calcination is also optimal;When mixing,Y and Al separation problems occur,and the YAP heterophase appears in the product,and the pure phase YAG nanoparticles with uniform particle size and particle size of about 100 nm can be obtained by stirring and mixing.In order to completely solve the problem of heterogeneous residue,this paper explored the preparation of YAG:Ce³⁺phosphor by nano-salt assisted sol-gel method.In this paper,YAG precursor sol was used to impregnate nano-potassium sulfate,and YAG precursor dry gel was formed between the gaps of nano-sulfate potassium salt particles.After high-temperature calcination,pure phase YAG particles with particle size below 50 nm and good dispersibility were prepared.The nano YAG phosphor exhibits good luminescence properties and can be transparently dispersed in an organic solvent.