Improvement Of Luminescence Properties Of Small-gage YAG:Ce³⁺ Phosphors

With the progress of society,the protection of the environment and energy has attracted more and more attention.For a long time,lighting has accounted for a considerable proportion of energy consumption.Therefore,white LEDs with advantages such as energy saving,environmental protection and long life have gradually entered our lives.The yttrium aluminum garnet light-emitting material represented by YAG:Ce³⁺has stable physical and chemical properties and excellent luminous properties.And it has become the most commonly used phosphor for white LEDs.In this paper,YAG:Ce³⁺phosphor was used as the research object.The molten salt method was used to prepare the phosphor,and the optimal process route for phosphor preparation was determined.Compared with the phosphor prepared by the high-temperature solid-phase method,it was found that the phosphor prepared by the molten salt method has higher luminous intensity,relatively easier particle size control.The YAG:Ce³⁺phosphor prepared by the molten salt method is further subjected to post-treatment processes such as particle size separation and heat treatment to obtain a phosphor with high luminous performance and controllable particle size.The specific research content is as follows:?1?Using the luminous intensity as an index,the optimal experimental conditions of the molten salt method are studied,including the amount of cerium,the ratio of salt to material?the ratio of the amount of molten salt and the amount of the raw material?,the synthetic raw materials of different particle sizes,the reaction temperature,and burning time.And then comparing the micro-morphology and luminescence performance of the screened sample and the sample synthesized by high temperature solid phase method.The research results show that when the yttrium oxide with a central particle diameter of D50=3.5?m and the alumina with a central particle diameter of D50=1?m are used,under the condition that the reaction temperature is 1300?and the holding time is 3 h and the salt-to-material ratio is 3:1,phosphor has the highest luminous intensity,uniform particle size,and good dispersibility.The YAG:Ce³⁺phosphor synthesized by the molten salt method is compared with the high-temperature solid-phase method.It was found that the YAG:Ce³⁺phosphor synthesized by the molten salt method has higher luminous intensity and more uniform crystal grains.?2?The effects of post-treatment process on particle size control and luminous properties were explored.The sand and ball milling process conditions were compared.The effects of grinding time,rotation speed,and ball-to-material ratio on the structure and performance of YAG:Ce³⁺phosphor were studied.Then the best way to sort the phosphor was screened.The screened samples were heat treated.Then the effects of heat treatment temperature,holding time and reaction atmosphere conditions on the luminous properties were studied.The results show that the ball milling method has less damage to the structure and luminous performance of YAG:Ce³⁺phosphor.Under the conditions of a ball radius of0.3 mm,a ball-to-material ratio of 4:1 and a rotation speed of 400 r,the loss of phosphor luminous intensity is lowest when the ball is milled to D50=5.0?m or less.The heat treatment of the sample shows that the luminous intensity of the sample increases the most when the sintering temperature is 1100?and the holding time is 3 h in a reducing atmosphere.?3?The effect of SP enhancement of silver island film and composite film of silica and silver on YAG:Ce³⁺phosphor was explored.As a result,it was found that the luminescence performance of the sample increased the most when silver was deposited for5 min.When the SiO₂ film is deposited for 2 minutes,the luminous performance of the sample will be improved again.Finally,the mechanism of silver island film fluorescence enhancement was analyzed.