Research On Manganese-doped Light Conversion Agent For Agricultural Application

In recent years,due to agricultural resource overexploitation,groundwater overdraft and environmental pollution and so on,agricultural sustainable development face major challenges.To optimize the existing cultivated land development and improve the unit yield of crops are of great significance to our country agricultural sustainable development.The light conversion agent plays a more and more important role in agricultural production.Agricultural plastic films,in which adding the light conversion agent,can greatly improve the utilization ratio of sunlight and further increase the agricultural production.In the plant factory lighting,the light conversion agent can be used to design plant growth LED according to the needs of plant growth.Therefore,in order to achieve efficient optical agriculture,it is very important to develop the light conversion agent which has high efficient,low cost and good spectral matching.Aluminate phosphors have attracted substantial attentions owing to their superior characteristics such as simple preparation process,widely material sources,low cost,good chemical stability and thermal stability,etc.Especially the manganese-doped aluminate phosphor has always been an important research object in the field of luminescent material,it has a broad prospect in agriculture application.The aim of this thesis is to obtain excellent light conversion agent,which focuses on the manganese-doped aluminate phosphors.To obtain simple synthetic process,good stability,well spectral matching,low cost inorganic light conversion agent for modern ecological high value agriculture,many control methods are applied such as process condition optimization,matrix modification and co-doped ions.The main research content is as follows:?1?Sr₂MgAl₂₂O₃₆:Mn⁴⁺was prepared by a high-temperature solid-state method.The light conversion agent can be excited with the light in the range of 250 nm-500 nm,and give intensitive red emission in 659 nm,which is matching well with chlorophyll absorption spectrum.By the methods of adding ammonium chloride,boric acid flux and matrix modification can improve Sr₂MgAl₂₂O₃₆:Mn⁴⁺luminescence performance.The most obvious effect is adding 2.0 wt.%of boric acid flux,which is helpful to obtain red phosphors with uniformity morphology.?2?The application characteristics of CaAl₁₂O₁₉:Mn⁴⁺phosphor,such as optical light bleaching resistance and thermal stability,can be obviously improved by silica coating?using ethyl silicate as silicon source?.Co-doping Mg,Y cations within in the CaAl₁₂O₁₉host in a controlled manner resulted red/far-red ratio-tunable luminescent properties.The emission bands are well-matched with the absorption band of phytochrome,which indicating that they have tremendous potential as lighting systems for plant growth.?3?CaYAlO₄:Mn⁴⁺were also prepared by a high-temperature solid-state method and their photoluminescent properties were discussed.When calcination temperature is over1450oC,it is easily to get the pure phase samples.The Mn⁴⁺-doped phosphor exhibits 710nm deep red emission and it has strong absorption in the UV and blue light region.It can be improved absorption efficiency in the blue area by changing the calcination temperature and concentration of manganese ion,or co-doped ions.