Y2-xLaxMo3O12制备及其热膨胀性能研究本科.doc

本科生毕业论文 毕业论文题目Y2-xLaxMo3O12制备及其热膨胀性能研究 所 在 学 院 物理科学与技术学院 专业及班级 物理 0801 完 成 日 期 2012年 5 月 6 日 Y2-xLaxMo3O12制备及其热膨胀性能研究(x=0,0.5,2) 摘要 以Y2O3、La23和MoO3为原料，采用固相反应法制备Y2-xLaxMo3O12(x=0,0.5,2)陶瓷材料样品。利用X射线粉末衍射和场发射扫描电子显微镜分别对样品进行物相、晶体结构分析以及形貌观察；通过热重分析了样品的热性能；采用热膨胀仪测定了样品的热膨胀系数。结果表明:Y1.5La0.5Mo3O12是单斜系晶体，其结构类型与Tb2Mo3O12相同，而且没有吸水特性。与Y2Mo3O12和La2Mo3O12相比，Y1.5La0.5Mo3O12晶胞更密集，其相对密度达到94.12%的理论值。最重要的是，它表现出了几乎为零的热膨胀率，178°C~ 600°C的热膨胀系数是0.87×10-6K-1。Y2Mo3O12是负热膨胀材料而La2Mo3O12是正热膨胀材料，它们的热膨胀系数分别为-12.06×10-6 K-1和8.88×10-6 K-1。 关键词：钼酸盐；陶瓷；晶体结构；热膨胀 Abstract The samples of Y2-xLaxMo3O12 (x=0, 0.5, 2) ceramics were prepared by theconventional solid-state reaction method using Y2O3、La203 and MoO3.The phase,crystal and morphology of the ceramics were characterized by powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) respectively . The thermodynamic property of the samples was characterized by thermo gravimetric analysis(TGA). The thermal expansion coefficients of the samples were measured by thermal dilatometer. Results indicate that the Y1.5La0.5Mo3O12 crystallizes in monoclinic Tb2Mo3O12-type structure and it is non-hygroscopic. The Y1.5La0.5Mo3O12 ceramic is denser than the Y2Mo3O12 and La2Mo3O12 ceramics, and its relative density can reach 94.12% of the theoretical value. Most importantly, it shows almost zero thermal expansion and its thermal coefficient is 0.87×10-6K-1 from 178°C to 600°C. Y2Mo3O12 ceramic shows negative thermal expansion whereas La2Mo3O12 ceramic shows positive thermal expansion, their thermal expansion coefficients being -12.06×10-6 K-1 and 8.88×10-6 K-1 ,respectively . Key words: Molybdates; ceramics; Crystal structure; Thermal expansion 目录 一 引言………………………………………………………………………………3 1.1研究背景 ……………………………………………………………………3 1.2研究概况 ……………………………………………………………………3 1.3发展趋势 ……………………………………………………………………4 1.4应用前景 ……………………………………………………………………5 1.5负热膨