Microwave Dielectric Loss And The Size Effect Of Luminescence Of Rare Earth Fluorescent Material For LED

Light emitting diode (LED) in solid state lighting (SSL) has being evolved into a huge industrialization chain covering upstream of substrate and epitaxy growth, mid-stream of chip and packaging and downstream of applications. The generation of white light by combining AlInGaN blue chip with YAG:Ce3+phosphor has to be color added by the600-620nm orange-red component to increase correlated color temperature (CCT). In special biological LED lighting, longer wavelength such as660nm-featured red emission is highly required. For this purpose, this thesis deals with a high-efficiency light-emitting rare earth phosphor material (Ba, Sr)MgSi2O8:Eu2+, Mn2+(BSMS-EM) prepared by high-temperature microwave (MW) firing procedure, accounting the interaction of MW field and solid material, paying attention on the dielectric properties of the phosphor, microwave thermal and non-thermal effects of light-emitting material composition, crystal structure, size and morphology, surface modification and its luminescence properties were investigated. The major achievements are summarized as follows.A. The dielectric and magnetic properties of material components in Eu2+and Mn2+co-doped (Ba, Sr)3MgSi2O8were measured and those of being fired material during forming compound were interpreted base on the MW thermal and non-thermal mechanisms closely relevant to structure, size and photoluminescence properties of phosphor.B. A simultaneous emission of both red and blue emission in the same BSMS-EM with660nm-featured was achieved by MW. The blue emission peak of432nm is attributed to the4f-5d of the Eu2+level transition while that of the660nm-featured red peak is ascribed to the transferred energy from Eu+to Mn+.C. The crystallographic and MW non-thermal effect were employed to interpret the grain growth/particle size of the phosphor of BSMS-EM. The’defocusing’effect of MW probably results in small particle in MW firing by effectively suppressing the grain growth compared with conventional high temperature solid synthesis (SS) procedure. In particular, The formation of impurity phases (Ba, Sr)2SiO4was found to be effectively suppressed by increasing the free energy of the crystal surface thereby causing the grain abnormal growth..D. The chemical stability of the BSMS-EM was evaluated by B2O3coating acid and soaking experiments.The results obtained in this thesis address some key issues relevant to the material (Ba, Sr)3MgSi2Og:Eu2+, Mn2+phosphor prepared by MW, providing a further understanding the role of microwave field effect, including processing, crystal structure and luminescence properties.