| Rare-earth doped luminescent materials have been widely used in several fields such as electric light source illumination,color developing materials for televisions,agricultural light conversion materials,X-ray phosphor powders,luminescent coatings,and luminous ink and so on because of their irreplaceable advantages.China has a dominant resource advantage in the application of rare-earth and a large variety of rare-earth resources.However,the utilization of technologies has the less competitive advantage.There is a large proportion of exporting raw materials and crude products while the semi-finished products and finished products highly rely on importing.In recent years,a large number of researches on the development and application of rare-earth doped functional materials have been done in China.However,there is still a gap with the advanced level in the world.Preparation methods have significant influence on luminescent properties of phosphors.Therefore,selecting a proper preparation method is an important means to improve the properties of phosphors.In this paper,a new synthetic method-high temperature mechanochemical method is explored to prepare rare-earth doped phosphors.The effects of different process conditions on the structure and luminescence properties of the materials are studied,and the optimum conditions for the preparation of phosphor are obtained.In addition,it also compares the influence of high temperature mechanochemical method with traditional preparation methods on the structure and luminescent properties of the phosphors.The optimal calcination condition for chemical precipitation method to prepare Y2O3:Eu3+phosphors are 800? for 3h and the amount of Eu3+-doped is 11 mol%.The optimal preparation conditions to prepare Y2O3:Eu3+phosphors by high-temperature mechanochemical method are determined as follows:milling conditions are 600? for 3h,the amount of Eu3+-doped is 12mol%and the ball-to-powder weight ratio is 15:1.Meanwhile,compared with chemical precipitation method,the calcination temperature has decreased by 200? and the prepared sample showed smaller particle size from about 10?m to 20?m and better dispersibility with high-temperature mechanochemical method.When ZnO:Eu3+samples were prepared by chemical precipitation method,it is optimal to calcine the precursors for 3 h at 900? with the optimal Eu3+ Uoping content of 1.0mol%.The optimal processing condition for the ZnO:Eu3+samples is to mill for 3h at 450? with doping 2.5mol%Eu3+ when the precursors were prepared by high-temperature mechanochemical method and the ball-to-powder weight ratio is 20:1.Compared with chemical precipitation method,the preparation temperature has decreased 450? and the prepared phosphors appear better dispersivity with high-temperature mechanochemical method.The optimal preparation conditions for preparation of Sr2CeO4:Eu3+ phosphors using high-temperature mechano-chemical method(HTMC)are such that the optimal doping content of Eu3+ is 12 mol%and calcining of the precursors at 900? for 2 h,respectively:however,preparation of Sr2CeO4:Eu3+ powder using the traditional high-temperature solid-phase method usually must be conducted at a temperature greater than 1000? for a longer calcination time.Compared with the traditional high-temperature solid-state method,the temperature and reaction time decrease when using the proposed HTMP technique.Compared with the citric acid sol-gel method,the temperature can be decreased by 300?when using HTMP.Furthermore,the phosphors obtained by use of the HTMP method exhibited better luminescence,a smaller mean average particle size,a narrower particle size distribution,and a more uniform dispersion.The optimal processing conditions to prepare SiO2:Eu3+ samples by sol-gel method are that the optimal doping content of Eu3+is 2.0mol%and calcining them for 2h in the muffle furnace at 900?.When SiO2:Eu3+samples obtained by high-temperature mechanochemical method,the optimal processing conditions are that the doping content of Eu3 is 4.0mol%and calcining them at 600? for 2h with the ball-to-powder ratio of 10:1.Compared with sol-gel method,the preparation temperature has decreased 300? and the phosphors with higher luminescent intensity can be prepared by high-temperature mechanochemical method.The calcination temperature needs to reach 1000? for 2h to prepare YAG:Ce3+phosphors via chemical precipitation method.However,the optimal high temperature milling conditions to prepare YAG:Ce3+ phosphors by high-temperature mechanochemical method are 700? for 2h.Compared with chemical precipitation method,the synthesis temperature has decreased by 300? as well as the phosphors with higher luminescent intensity and better crystallinity can be prepared by high-temperature mechanochemical method.The optimal high temperature milling conditions to prepare CTMA phosphors by high-temperature mechanochemical processing method are 900? for 1h.In addition,the CTMA phosphors prepared by high-temperature mechanochemical processing method have favorable dispersibility with the grain sizes from 10 ?m to 20?m.The high-temperature mechanochemical method can significantly reduce the activation energy of the reaction,greatly improve the activity of the powder particles and refine the crystal grains,improve the uniformity of the product particle distribution,enhance the interfacial bonding performance among the matrixs,promote solid state ion diffusion,and induce low-temperature chemistry reaction.Compared with the traditional high-temperature sintering technology,this method has the mechanical force at the same time of sintering,which can effectively prevent the growth of the material particles due to the increase of temperature,which is beneficial to obtain the powder material with uniform dispersion and regular appearance;In addition,due to the transformation from mechanical.energy to heat energy providing a large amount of heat for the system,the temperature and time of high-temperature heating process are reduced in the sintering process and energy is saved.The research results have important theoretical guidance and practical value to prepare rare-earth doped luminescent material with high quality and low cost. |
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