Gd-Tb-Co三元相图及(Gd_1-xTb_x)Co₂化合物的磁热效应研究

【作者】 周开文；

【导师】 庄应烘；

【作者基本信息】 广西大学 ， 材料物理与化学， 2006， 硕士

【摘要】 本论文分两个方面的工作。一是Gd-Tb-Co三元相图的测定；二是Gd_1-xTb_xCo₂（x=0到1）系列化合物的磁热效应的研究。 采用X射线粉末衍射法、热分析法、光学金相显微镜分析法，同时结合扫描电镜分析法，研究并确定了Gd-Tb-Co三元系合金相图500℃等温截面。结果表明在这一等温截面中，存在有9个单相区、8个两相区。实验中没有发现三元化合物和三相区的存在。化合物Gd₂Co₁₇和Tb₂Co₁₇，Gd₂Co₇和Tb₂Co₇，GdCo₃和TbCo₃，GdCo₂和TbCo₂，Gd₄Co₃和Tb₄Co₃，Gd₁₂Co₇和Tb₁₂Co₇，Gd₃Co和Tb₃Co，以及Gd和Tb形成连续固溶体。另外还测定了二元系Gd_1-xTb_xCo₂（x从0到1）的变温截面。 在化合物的磁热效应研究方面，利用振动样品磁强计对(Gd_1-xTb_x)Co₂（x=0，0.2，0.4，0.5，0.6，0.7，0.8和1）几个合金进行了磁性测量。结果表明，合金的居里温度T_C随x的增大而减小，而当x=0.6时，其T_C接近室温300K。化合物的磁熵变|ΔS_M|随x的增大而增加，在0到2特斯拉磁场下，最大磁熵变值为1.7J／kgK到3.6J／kgK。所有这些化合物表现为二级磁相变。更多还原

【Abstract】 This paper includes two parts of study work: one is about the isothermal section of the phase diagram of the Gd-Tb-Co ternary system at 500 °C,the other one is about magnetocaloric effects in (Gd_1-xTb_x)Co₂.The isothermal section of the phase diagram of the Gd-Tb-Co ternary system at 500°C was investigated by X-ray powder diffraction, differential thermal analysis and metallographic analysis techniques. In this isothermal section, there are nine single-phase regions, eight two-phase regions and none three-phase region. No ternary compound was found. The compounds Gd₂Co₁₇ and Tb₂Co₁₇, Gd₂Co₇ and Tb₂Co₇, GdCo₃ and TbCo₃, GdCo₂ and TbCo₂, Gd₄Co₃ and Tb₄Co-3, Gd₁₂Co₇ and Tb₁₂Co₇, Gd₃Co and TD₃Co, Gd and Tb form a continuous series of solid solutions. In addition, we experimentally determined the vertical section of pseudobinary system of Gd_1-xTb_xCo₂（x from 0 to 1） series alloys.About magnetocaloric effects in (Gd_1-xTb_x)Co2: The structures and magnetocaloric effects of (Gd_1-xTb_x)Co₂ （x=0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, and 1） pseudobinary compounds were investigated by X-ray powder diffraction and magnetic properties measurement. The results show that the Tc of the alloy is near room temperature when X=0.6. The magnetic entropy changes of the compounds increase from 1.7 J/kgK to 3.6 J/kgK with increasing the content of Tb under an applied field up to 2T. All the compounds exhibit second order magnetic change.更多还原