摘要
Zn^2＋ - or Ti^4＋ -substituted cordierites with the nominal compositions of Mg1 .6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The structure of the substituted eordierites was characterized by X- ray diffraction （ XRD ）, infrared （ 1R ） spectroscopy and 29 Si magic angle spinning （ MAS ） nuclear magnetic resonance （ NMR ）. The infoared radiation properties were investigated in the bands within 2.5-25μm. Compared with the na-substituted cordierite composition （ Mg2 Al4 Si5 O18 ）, Zn^2＋ - or Ti^4＋ -substituted cordierites show superior infrared properties. XRD and IR results confirm the formation of hexagonal a-eordierite as the main eo＇stal phase for the substituted cordierites. 29 Si MAS NMR result indicates that Zn^2＋ or Ti^4＋ Substitutions for partial Mg^2＋ of a-eordierite promoted the ordering of the distribution oral and Si atoms in T1 （ tetrahedra connecting six-raembered rings together with [ MgO6] octahedra ） and T2 （ tetraheda forming six-reentered rings） tetrahedral sites. This resulted in a lattice deformation and increased the anharmonicity of polarization vibration, which is responsible for the improvement of infrared radiation properties of the substituted eordierites.
Zn^2＋ - or Ti^4＋ -substituted cordierites with the nominal compositions of Mg1 .6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The structure of the substituted eordierites was characterized by X- ray diffraction （ XRD ）, infrared （ 1R ） spectroscopy and 29 Si magic angle spinning （ MAS ） nuclear magnetic resonance （ NMR ）. The infoared radiation properties were investigated in the bands within 2.5-25μm. Compared with the na-substituted cordierite composition （ Mg2 Al4 Si5 O18 ）, Zn^2＋ - or Ti^4＋ -substituted cordierites show superior infrared properties. XRD and IR results confirm the formation of hexagonal a-eordierite as the main eo＇stal phase for the substituted cordierites. 29 Si MAS NMR result indicates that Zn^2＋ or Ti^4＋ Substitutions for partial Mg^2＋ of a-eordierite promoted the ordering of the distribution oral and Si atoms in T1 （ tetrahedra connecting six-raembered rings together with [ MgO6] octahedra ） and T2 （ tetraheda forming six-reentered rings） tetrahedral sites. This resulted in a lattice deformation and increased the anharmonicity of polarization vibration, which is responsible for the improvement of infrared radiation properties of the substituted eordierites.
基金
Funded by the National Natural Science Foundation of China(No.50342014 ) and Key Technology Project of Wuhan City(20026002093)
