Li Jiandi, Gong Aijun, Li Xingyan, He Yanfei, Li Jinsheng, Bai Yuzhen, Fan Rongrong
College of Chemistry and Biological Engineering, University of Science and Technology Beijing Beijing 100083 China
Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials, University of Science and Technology Beijing Beijing 100083 China.
RSC Adv. 2022 May 30;12(24):15348-15353. doi: 10.1039/d2ra01714h. eCollection 2022 May 17.
Lanthanum-based titanates have been attracting considerable interest by virtue of their structural operability and hence diverse physical properties. The preparation of lanthanum-based titanates with novel crystal structure is a fascinating task. In this work, we report the preparation of a cubic Ce TiO pyrochlore using the sol-gel method. The crystal structure, thermostability and magnetism were studied the temperature dependence of X-ray powder diffraction, X-ray photoelectron spectroscopy and magnetization measurements. It has been revealed that the as-prepared Ce TiO pyrochlore possesses a cubic symmetry (space group: 3̄), however there is an 18(1)% vacancy of Ce ions in the as-prepared samples. No distinct phase transition and thermal expansion anomaly were observed in the investigated temperature range from 300 K to 700 K. Intriguingly, lattice defects may favor the transformation of Ce valence from +3 to +4 and an unusual weak magnetic ordering state emerged up to 400 K. The persistence of magnetism at such high temperatures is rare and mysterious for cerium titanates. Our findings provide the possibility of adjusting the crystal structure and magnetic properties of cerium titanates, anticipated to the development of lanthanum-based oxides.
基于镧的钛酸盐因其结构可操作性以及由此产生的多种物理性质而备受关注。制备具有新颖晶体结构的基于镧的钛酸盐是一项引人入胜的任务。在这项工作中，我们报告了使用溶胶 - 凝胶法制备立方CeTiO烧绿石。通过X射线粉末衍射、X射线光电子能谱和磁化测量研究了其晶体结构、热稳定性和磁性与温度的关系。结果表明，所制备的CeTiO烧绿石具有立方对称性（空间群：3̄），然而在制备的样品中Ce离子存在18(1)%的空位。在300 K至700 K的研究温度范围内未观察到明显的相变和热膨胀异常。有趣的是，晶格缺陷可能有利于Ce价态从 +3转变为 +4，并且在高达400 K时出现了异常的弱磁有序状态。对于钛酸铈而言，在如此高的温度下磁性的持续存在是罕见且神秘的。我们的发现为调整钛酸铈的晶体结构和磁性提供了可能性，有望推动基于镧的氧化物的发展。
