Synthesis, structure and properties of new functional oxynitride ceramics

摘要

Novel metal oxynitrtides have been prepared by nitridation of amorphous metal oxide precursors obtained through citrate route. Their crystal structure, especially in O/N distribution and local bonding characteristics has been analyzed by using neutron diffraction, X-ray absorption and transmission electron microscopy, to investigate their electric and optical properties. In dielectric SrTaO₂N, crystal structure refinement suggested the short range O/N ordering and local tilting of cis -TaO₄N₂ octahedra, resulting in its unusual large permittivity. Its dense ceramics were sintered with SrCO₃ additive and exhibited superior dielectric constant above 1 × 104 at room temperature. New biphasic wurtzite and zinc-blende structure of gallium oxynitride nanowire was observed by using transmission electron microscopy. As-grown long gallium oxynitride nanowire exhibited a characteristic broad UV emission at 4.3 eV in its cathodoluminescene spectrum. New oxynitride phosphor having magnetoplumbite structure, LaAl₁₂(O,N)₁₉:Eu showed photoluminescence emission peak splitting due to Eu2+ site splitting to two crystallographic sites induced by the two kinds of anions in its crystal structure.