Li,Co共掺杂ZnO纳米颗粒的结构和磁性研究

Structure and Magnetic Property of(Li,Co)-Codoped ZnO Nanocrystals

利用溶胶-凝胶法制备了不同组分的Zn0.95-xCo0.05LixO纳米颗粒,并通过透射电子显微镜、X射线衍射、紫外-可见吸收光谱和振动样品磁强计对其结构和磁性进行了系统的研究。结果表明,当Li掺杂比例在7%以下时,Zn0.95-xCo0.05LixO纳米颗粒仍具有很好的ZnO六角纤锌矿结构,但随着Li掺杂量的增加,晶格常数a和c值略有减小;Zn0.95-xCo0.05LixO的室温铁磁性随x的增大而显著增强。当Li掺杂量达到9%时,在Zn0.95-xCo0.05LixO纳米颗粒的XRD谱中检测出第二相的LiCoO2団簇,样品的铁磁磁化强度明显下降。表征结果显示Li掺入Zn0.95Co0.05O的反应过程可以分为3个阶段。前两个阶段分别在材料中引入了Li′Zn深能级缺陷和Li+填隙离子,第三个阶段则产生了LiCoO2第二相结构。样品铁磁性的变化与Li掺杂引入的这些缺陷和第二相有关,可由束缚磁极化子(BMP)模型解释。

Zn0.95-xCo0.05LixO （ x = 0～0. 09 ） nano-crystals were synthesized by sol-gel method. Detailed characterization by XRD, UV-Vis absorption spec- trum, and vibration sample magnetometer （VSM） indicated that Li-Co co-doping did not change the Wurtzite structure of ZnO when x≤7%. With the increase of Li-dopant, the lattice constants a and c decreased owing to the substitution of Zn2＋ by Li ＋ ions, the ferromagnetism increased gradually. However, the ferromagnetism droped sharply when L-dopant increased to 9%. At the same time, second-phase clusters of LiCoO2 were detected in the XRD pattern and the lattice constants almost stopped decreasing. Exper imental results suggested that the reaction of Li incor- poration could be divided into 3 stages. Li＇Zn deep level defects and Li（ interstitials were induced into the material at the former two stages respectively, while the second-phase LiCoO2 formed at the third stage. These defects and second-phase structures induced by Li-doping played important roles in enhancing the ferromagnetism of the samples, which could be explained by the bound magneton polaron （BMP） model.