The Negative Thermal Expansion Of Sno <sub> 2 </ Sub>-of Zro <sub> 2 </ Sub>-2wo <sub> 3 </ Sub> Ceramic Materials Research

The negative thermal expansion SnO2-ZrO2-2WO3 system mini-crystal materials are prepared by glass technics. The negative thermal expansibility, expansion mechanics, micro-structure morphology and the relationship of the effects of compositions on the properties of SnO2-ZrO2-2WO3 system mini-crystal materials are investigated by thermal dilatometer (TD), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. Applying the treor90 software, the X-ray pattern of SnO2-ZrO2-2WO3 system mini-crystal materials is indexed. The structure type of it is confirmed, and the cell parameter is calculated. The crystallization activation energy is calculated. The glass stability criteria of kinetics,dynamics and thermodynamics is discussed. SnO2-ZrO2-2WO3 system phase diagram is described and analyzed. The big crystalloid of Sn20 is prepared. Research results are indicated as follows:When SnO2 composition is 5mol% and 25-80mol%, the positive thermal expansion mini-crystal materials are prepared. When SnO2 composition is 10mol%, 15 mol% and 20 mol% respectively, the negative thermal expansion can be found in a large temperature range. The linear thermal expansion coefficient of Sn20 is -2.396×10-6K-1 with the temperature range 298-1049K. Furthermore, doped Al2O3 has a great effect on the thermal expansion of SnO2-ZrO2-2WO3 system mini-crystal materials.The lattice type of SnO2-ZrO2-2WO3 system mini-crystal materials substituted for 5-60mol% SnO2 belongs to the orthorhombic system. The cell parameter range: a=9.145-9.201 A, b-12.070-12.686 A, c=9.085-9.117 A. However, the lattice type of Sn80 is the monoclinic system. The cell parameter: a=10. 939 A> b =11.973 A, c= 7.814 A.Due to the bridge oxygen landscape orientation between [(Zr/Sn)O6] octahedron and [WO3J tetrahedron, the negative thermal expansion substituted for 10-20mol% SnO2 is exhibited.By the Kg (T) criteria, the stability order of the SnO2-ZrO2-2WO3 system glasses as follows: Sn10 > Sn5 > Sn20 > Sn30 > Sn40 > Sn60 > Sn80; the stability order of the Sn20 system glasses as follows: A115> A120 A110>A15.According as the experimentations, the SnO2-ZrO2-2WO3 system phase diagram is described and analyzed. The big crystalloid of Sn20 is prepared.