In_2W_3O_(12)陶瓷的相变特性及其负热膨胀性能(英文)

Phase Transition and Negative Thermal Expansion in In_2W_3O_(12) Ceramics

以分析纯In2O3和WO3为原料,采用固相反应法制备In2W3O12陶瓷。利用X射线衍射仪、场发射扫描电子显微镜、热重分析仪、差示扫描量热仪和热机械分析仪对样品的物相组成、微观结构、相变和热膨胀特性进行了表征。结果表明:在900℃烧结6h可制备出纯的单斜相In2W3O12陶瓷,In2W3O12陶瓷断面晶粒均匀,平均尺寸为4～6μm。In2W3O12陶瓷在253.34℃发生单斜相到斜方相的相转变,单斜相的In2W3O12陶瓷显示正热膨胀,在27～249℃,其平均热膨胀系数为16.51×10-6℃-1,斜方相的In2W3O12陶瓷显示负热膨胀,在273～700℃,其平均热膨胀系数为-3.00×10-6℃-1。

Cubic HfW2O8ceramic was synthesized by a solid state reaction method with HfO2and WO3as raw materials.The phase compositions,microstructures,phase transition and negative thermal expansion(NTE)properties of the samples were characterized by X-ray diffraction,field emission scanning electron microscopy and thermal mechanical analysis,respectively. The results indicate that the cubic HfW2O8ceramic can be prepared viasintering at 1 200℃for 6hand quenching in deionized water.The cubic HfW2O8ceramic is compact with the small square grains.This ceramic exhibits an intensive negative thermal expansion property.Theαtoβstructure phase transition occurs at 182.5℃,leading to a decrease in the NTE coefficient of cubic HfW2O8ceramic.The NTE coefficient measured is—12.90×10—6 K—1 forα-HfW2O8,and—10.09×10—6 K—1 forβ-HfW2O8. The average NTE coefficient for the cubic HfW2O8ceramic is—11.46×10—6 K—1 in the range from 25to 600℃.The magnitude of NTE coefficient for the cubic HfW2O8ceramic is smaller due to the presence of the pores and micro-cracks in HfW2O8ceramic.