Sc2－xGaxW3O12体系负热膨胀性能研究

通过固相反应法，在1100 ℃下成功制备出了系列Ga掺杂Sc_2-xGa_xW₃O₁₂（x=0, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8）固溶体.X射线粉末衍射结构精修表明，Ga以替代Sc的形式成功进入Sc_2-xGa_xW₃O₁₂晶格，但不能获得端元组分Ga₂W₃关键词： 负热膨胀 热膨胀系数 Rietveld结构精修

Negative thermal expansion of Sc2-xGaxW3O12 solid solution

Series of Ga-doped Sc_2-xGa_xW₃O₁₂ samples (x=0, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8) were synthesized by solid state reaction at 1100 ℃. Rietveld refinement of the X-ray powder diffraction patterns show that Ga substituted Sc in Sc_2-xGa_xW₃O₁₂ structure successfully. The client component Ga₂W₃O₁₂ cannot be obtained in this work. The lattice parameters obtained by Rietveld refinement showed that all samples have negative thermal expansion between 25—1000 ℃. Lattice parameters a, c and cell volume of the Sc_2-xGa_xW₃O₁₂ decrease with the increases of Gallium content, but accompanied with the expansion of lattice parameter b. The average volume expansion coefficient also decreases with the increase of the Gallium content. As the temperature increases, the absolute value of the volume expansion coefficients decrease dramatically between room temperature and 300 ℃, but remain almost unchanged between 300 and 800 ℃, and decrease further at the temperature higher than 800 ℃, tending to zero and turning into positive expansion.