Structure, electrical conducting and thermal expansion properties of Ln0.6Sr0.4Co0.2Fe0.8O3 (Ln = La, Pr, Nd, Sm) perovskite-type complex oxides
Structure, electrical conducting and thermal expansion properties of Ln0.6Sr0.4Co0.2Fe0.8O3 (Ln = La, Pr, Nd, Sm) perovskite-type complex oxides
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DOI：
10.1016/j.jallcom.2006.04.005
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发表时间：
2007-02
影响因子：
6.2
通讯作者：
Qing Xu;Duanping Huang;Wen Chen;Feng Zhang;Bi-tao Wang
中科院分区：
文献类型：
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作者：
Qing Xu;Duanping Huang;Wen Chen;Feng Zhang;Bi-tao Wang
采用甘氨酸-硝酸盐法制备了细小、均匀的钙钛矿型Ln0.6Sr0.4Co0.2Fe0.803(Ln=La，Pr，Nd，Sm)粉末。研究了陶瓷的结构、导电性和热膨胀性能。结果表明，La~(3+)被较小的稀土离子取代后，晶体结构由斜方对称转变为正交对称，准立方晶格常数减小。结果表明，随着稀土阳离子尺寸的减小，材料的导电性能降低。与La0.6Sr0.4Co0.2Fe0.803相比，Pr0.6Sr0.4Co0.2Fe0.803和Nd0.6Sr0.4Co0.2Fe0.803的导电性能下降不明显，而Sm0.6Sr0.4Co0.2Fe0.803的导电性能下降到不能令人满意的程度。所有组合物在高温下的热膨胀都有明显的增加。这归因于氧损失和氧空位的形成导致的化学诱导的晶格膨胀。Pr0.6Sr0.4Co0.2Fe0.803和Nd0.6Sr0.4Co0.2Fe0.803具有较低的热膨胀系数，分别为14.2×10−6和13.2×10−6K−，平均在100~750℃和100~700℃之间。
Fine and uniform Ln0.6Sr0.4Co0.2Fe0.8O3(Ln=La, Pr, Nd, Sm) powders with a perovskite phase were produced using a glycine–nitrate process. The structure, electrical conducting and thermal expansion properties of the resulting ceramics were investigated. The results indicate that replacing La3+by smaller lanthanide cations led to a change in crystal structure from rhombohedral to orthorhombic symmetry and a decrease of the pseudo-cubic lattice constant. It was found that the electrical conducting properties decrease with reducing lanthanide cation size. Compared with La0.6Sr0.4Co0.2Fe0.8O3, the degradation of the electrical conducting properties in Pr0.6Sr0.4Co0.2Fe0.8O3and Nd0.6Sr0.4Co0.2Fe0.8O3is not pronounced, whereas the electrical conducting properties of Sm0.6Sr0.4Co0.2Fe0.8O3decline to an unsatisfactory level. There is an evident increase in thermal expansion at high temperatures for all the compositions. This is attributed to a chemically induced lattice expansion due to oxygen lose and formation of oxygen vacancies. Pr0.6Sr0.4Co0.2Fe0.8O3and Nd0.6Sr0.4Co0.2Fe0.8O3present relatively low thermal expansion coefficient values of 14.2×10−6and 13.2×10−6K−1averaged between 100–750 and 100–700°C, respectively.