新型氮(氧)化合物的合成、结构及发光/介电性能的研究

Oxonitride and nitride luminescent materials and dielectric materials are in the new research area of inorganic solid materials. Compared with oxygen, nitrogen has smaller electonegativity and larger atomic polarization. These may benefit the red-shifts of excitation and emission spectra of rare earth activators in the materials and make the phosphors suitable for the white-LED applications，and also may help the permittivity enhancement of the materials. Since the synthesis conditions are severe, the number of oxonitride and nitride materials is not as many as oxides. In this project, we choose related oxide materials as the structure modes and try to design and synthesize novel phases of (oxo)nitridoaluminates,(oxo)nitridosilicates,(oxo)nitridotitanate,(oxo)nitrido-niobates and (oxo)nitridotantalates with the guidance of element replacement, block replacement and charge-balance control.With the combination of X-ray, electron and neutron diffractions as well as Rietveld refinement method, we analyze the structures of the new phases.Furthermore we investigate the luminescent properties of rare earth doped (oxo)nitridoaluminates and (oxo)nitridosilicates as well as dielectric properties of oxonitridotitanate, oxonitridoniobates and oxonitridotantalates. With the assistance of the first-principle calculations, we may calculate the band structure, the formation enthalpy of doping defects and lattice vibration modes of selected materials for further understanding the mechanisms of the material properties.

氮氧化物与氮化物荧光材料和电介质材料是无机固体材料研究的新领域。相比于氧元素，氮元素具有小的电负性和大的极化率。这些有利于荧光材料中稀土激活剂激发和发射光谱的红移，使其适合半导体照明器件的要求，也有利于电介质材料介电常数的提高。然而由于氮氧化物和氮化物苛刻的合成条件，人们已获得的这类材料的种类远不及氧化物材料丰富。本课题以已有氧化物材料为结构母板或模板，通过利用元素取代、模块取代和电荷平衡的设计思路,尝试设计合成铝基、硅基、钛基、铌基和钽基氮氧化物与氮化物新物相；利用多种衍射技术和结构精修的方法解析新物相的结构；研究稀土离子在铝基和硅基新材料中的发光；研究钛基、铌基和钽基新材料的介电性能。为了深入理解材料性能的微观机理，研究中借助第一性原理计算和分析材料的能带结构、掺杂缺陷形成能和振动模的原子振动形式。

与氧元素相比，氮元素具有大的极化率和小的电负性。这些特性有利于氮化物和氮氧化物电介质材料介电常数的提高，也有利于氮化物和氮氧化物荧光材料中稀土激活剂激发和发射光谱的红移，使其适合半导体照明器件的要求。本课题获得了一种具有正交结构的新型氮化物介电材料CaTiN2，其介电常数在1000量级。该研究开拓了介电材料研究的新领域。获得了两种新型氮氧化物荧光材料：具有正交结构的Ba3Si3O3N4:Eu2+和具有单斜结构的Ca4Si4O9N2:Eu2+。前者在近紫外光和蓝光的激发下发出红色荧光，而后者发出绿色荧光。两种材料有望在白光LED光源中获得应用。研究了Ce3+-Yb3+共激活的LaBO3的荧光性能，该材料在330nm紫外线激发下，仅发射近紫外光和近红外光，而不发射可见光，该材料在防伪技术中可能获得应用。