【作者】 李延春；

【导师】 王文魁；

【作者基本信息】 燕山大学 ， 材料物理与化学， 2001， 硕士

【摘要】 本论文对闭管化学气相生长高质量β-FeSi₂单晶的工艺条件、β-FeSi₂单晶的晶体结构及其高压相演化进行了深入研究。 1、利用化学气相输运方法，以碘作为传输剂，在封闭的石英安瓿中生长了优质新型光电及热电半导体材料β-FeSi₂单晶。深入研究了生长工艺对单晶质量、形态等的影响，除得到大尺寸针状β-FeSi₂单晶外，还得到了未见文献报道的大尺寸颗粒状单晶。通过改变衬底温度，得到了四面体柱状优质的α-FeSi₂单晶。 2．研究了重力方向对晶体生长的影响。结果表明：传质方向与重力方向垂直的安瓿和传质方向与重力方向相反的安瓿中，传质过程受对流控制；而传质方向与重力方向相同的安瓿中，传质过程受扩散控制。对流控制的两个安瓿的生长条件比较接近，得到的晶粒形貌也很相似，都具有棱锥形貌和不规则形貌；而在扩散控制的安瓿中得到的晶粒是片状和板状的。这说明流场与重力场取向不同，影响了安瓿内的传质过程，进而影响了晶体的生长形貌。 3．利用四探针法测量了大尺寸单晶颗粒电阻率随温度的变化关系，发现电阻率随着温度的倒数（1/T）的增大而增大。 4．利用金刚石压砧和同步辐射X-射线衍射技术原位研究了β-FeSi₂的高压相演化，发现在4.3 GPa出现相变，22 GPa相变完成，相变产物具有四方结构，其晶格常数为： a=b=0.4393nm,c=2.0507nm更多还原

【Abstract】 Crystal growth technology and crystal structure of high quality β-FeSi₂ single crystals grown from vapor by employing chemical vapor transport technique and its phase transition under high pressure were studied. 1. Single crystals of β-FeSi₂, as new photoeletric and thermoelectric material have been grown from vapor by employing chemical vapor transport technique with iodine as transport agent in a closed ampoule. Needle-like single crystals were gained and Grain-like single crystals were obtained. By changing substrate temperature, tetrahedral high quality β-FeSi₂ single crystals were grown. 2. The effects of orientation of the direction of mass transport in gravity field on the single crystal growth of (β-FeSi₂ were studied. As the angle between gravity and mass transport direction was 900 or 1800, mass transport process was convection-dominated regime. And as the angle between gravity and mass transport direction was 00, it was diffusion-dominated. In convection-dominated cases, morphologies of β-FeSi₂ single crystals were similar and pyramid-like. In the diffusion dominated case, β-FeSi₂ single crystals were lamellate. This shows that the processes of mass transport are different for mass transport direction in gravity field. 3. Temperature dependence of electrical resistivity of β-FeSi₂ single crystals was measured by four-probe method. It was found that electrical resistivity increases with increasing lIT. 4. Phase transition of β-FeSi₂ single crystals at high pressure with Diamond Anvil Cell Apparatus were in situ studied by synchrotron radiation X-ray diffraction. Phase transition began at 4.3GPa and completed at 22GPa. The product of phase transition is tetragonal and its lattice constants are a40.4393nm, and c2.0507.更多还原