Synthesis, Thermal Expansion And Electrical Properties Of Al-Y₂W₃O₁₂ Composites

With the development of science and technology, the material requirements of modern high-tech industry is higher and higher. People are becoming more and more favored by multifunctional composite materials. Negative thermal expansion materials have the property of volume shrinkage with the temperature rising. The composite materials of NTE materials and conventional thermal expansion material could be the material of adjustable expansion coefficient even the zero inflation.In recent years, the composites of NTE materials and common materials has become one of the hot topics in the field of material preparation. Research on composites with respect to NTE materials and common materials typically focus on NTE materials and metals, NTE materials and ceramic materials, and NTE materials and functional polymers. A breakthrough in terms of techniques in integrated circuit and chip package design with regard to the composite of NTE and metal is expected. The NTE and metal composite is also expected to be capable of satisfying heat loss demand, electric conduction demand, low expansion demand, and heat matching with a silicon base.Y2W3O12was synthesized by coprecipitation method, while the Al-Y2W3O12composites were synthesized by solid-state method. The resultant Y2W3O12powders and commercial Al powders (obtained by passing through a200-mesh sieve) were mixed at different Al:Y2W3O12mass ratios. The mixtures were heated for4h in the different temperatures (600℃.630℃.660℃or700℃). The properties and microstructure of the Al and Y2W3O12products with different ratios and different mass ratios were investigated. The X-ray diffraction (XRD) analysis of the Al-Y2W3O12composites show that there was no substitution of Y by Al. That is no change with temperature and mass ratios.The scanning electron microscopy (SEM) analysis of the surface morphology of Al-Y2W3O12composites show that the mixture which have been heated for4h in the630℃present a unique structure that bulks of Al are embedded by little particles of Y2W3O12. However the composites were sintering in the conditions of other temperature do not show embedded composite structure.Expansion coefficient was observed using a thermal dilatometer. We found that Y2W3O12has a high water absorption capability. When the mixtures of Al and Y2W3O12at a mass ratio of2:8at660℃and700℃, the water absorption are stronger than the pure Y2W3O12. The samples sintered at630℃show a distinctively thermal performance——When the mass ratio was7:3at temperatures ranging from room temperature (RT) to600℃, the temples have a linear expansion coefficient of14.76×10-6/K, which is half that of Al (27.52×10-6/K), and the samples show the Water absorption hardly.Electrical performance was observed using an electrochemical workstation. The results showed that when the sample was sintered by a mass ratio of7:3at630℃, it shows a good conductivity as18.2S/m, which is about half of Al as35.71S/m. Thus, the phenomenon that ceramics is not conductive has been changed. That is to say, the Y2W3O12composite materials with a low expansion coefficient and high electrical conductivity can be get in certain temperature conditions.