【作者】 王德刘；

【导师】 傅仁利；

【作者基本信息】 南京航空航天大学 ， 材料学， 2009， 硕士

【摘要】 采用高温固相反应(SSR)和碳热还原氮化(CRN)两种工艺制备了稀土掺杂α-SiAlON光转换材料。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、荧光分光光度计对样品进行了分析,研究了稀土掺杂离子、主晶格组成、合成工艺参数等对光转换材料荧光性能的影响。研究结果表明:(1)对于高温固相反应α-SiAlON光转换材料,样品均以α-SiAlON为主晶相。Eu2+等稀土掺杂离子在α-SiAlON主晶格中实现了良好掺杂。通过改变稀土掺杂离子浓度,稳定离子种类,m值以及工艺参数,可以对光转换材料进行有效的光谱剪裁。对于Eu2+,Tb3+,Dy3+掺杂Ca-α-SiAlON在色度图上分别位于黄绿光区、绿光区和近白光区。对于Li+, Ca2+, Y3+稳定α-SiAlON:Eu2+光转换材料,Ca2+稳定的样品具有最高的发光强度。对于20at.% Eu2+掺杂Ca-α-SiAlON,主晶格组成为m=2.5的样品荧光强度最高。提高合成温度,可以改善Eu2+离子的分布均匀性。采用氢气,氮气混合气合成的Ca-α-SiAlON:Eu2+的发光强度要高于氮气气氛合成的样品。(2)对于碳热还原氮化Ca-α-SiAlON光转换材料,以SiO2作为起始材料碳热合成的样品以非晶玻璃的形式存在,而以Si3N4作为起始材料碳热合成的样品没有SiC杂相,为单相Ca-α-SiAlON,同时样品表面存在少量的在脱碳过程中生成的非晶硅酸盐。非晶玻璃样品的激发光谱范围为:~ 260nm-380 nm,发射光谱峰值波长为:~ 425nm-450 nm。随着Eu2+掺杂量的增加,荧光光谱出现了红移和猝灭现象。Si3N4碳热合成Ca-α-SiAlON光转换材料的样品,其荧光光谱有一定的蓝移,同时短波段的吸收峰消失。Si3N4碳热合成Ca-α-SiAlON:Eu2+机理分析表明,起始材料首先生成钙铝酸盐中间相。由钙铝酸盐中间相产生的低温共晶液相促进了氮化物层的形核长大。随着温度和时间的增加,氮化物层和Si3N4发生反应,最终合成Ca-α-SiAlON:Eu2+光转换材料。更多还原

【Abstract】 Rare-earth dopedα-SiAlON phosphors were prepared by solid state reaction (SSR) and carbothermal reduction and nitridation (CRN) method, respectively. Using X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and fluorescent spectrophotometer, the influences of different rare-earth ions, compositions and sintering process on optical properties ofα-SiAlON phosphors were studied. Experimental results show: (i) Theα-SiAlON phosphors prepared by SSR are consisted of singleα-SiAlON phase. Rare-earth ions (e.g., Eu2+) enter in the lattice ofα-SiAlON. The optical properties of phosphors can be tailored by varying the concentration and type of rare-earth ion, m value and sintering process. In chromaticity diagram, Eu2+, Tb3+ or Dy3+ doped Ca-α-SiAlON phospors show yellowish-green emitting, green emitting, and near white emitting, respectively. Ca2+ stablized samples have the highest photoluminescence (PL) intensity among Li+, Ca2+, or Y3+ stablizedα-SiAlON phospors. The phosphors with m=2.5 have the strongest PL emitting among 20 at.% Eu2+ doped Ca-α-SiAlON. Rising sintering temperature can improve the uniformity of Eu2+ ion dispersion inα-SiAlON lattice. Ca-α-SiAlON:Eu2+ phosphors synthesized in the mixture of hydrogen and nitrogen atmosphere had stronger emission intensity than that synthesized in nitrogen atmosphere. (ii) The Ca-α-SiAlON phosphors prepared by CRN are single Ca-α-SiAlON phase synthesized from Si3N4 without by-products such as SiC while amorphous glass synthesized from SiO2. The excitation spectra of amorphous glass cover the range of ~ 260nm-380 nm, and the emission bands centered at ~ 425nm-450 nm are observed in the emission spectra. Both the phenomena of red shift and concentration quenching are observed with the Eu2+ content increase. The spectra of the Ca-α-SiAlON phosphors synthesized from Si3N4 show a small blue-shift and disappearance of low wavelength absorption. A model for carbothermal synthesis was developed to interpret the mechanism of carbothermal reduction process. The intermediate Ca-aluminates formed from the starting materials favour the occurrence of eutectic liquid at relatively low temperature, whose increasing saturation with the growing species eventually enables nucleation and growth of Me3Nv layers. Further increase of temperature and time, favors the reaction between Me3Nv and Si3N4 yielding Ca-α-SiAlON:Eu2+ phosphors.更多还原