Zn_(1-x)Co_xO的结构与光吸收对比研究

采用共沉淀法制备草酸盐前躯体,前躯体低温分解制备系列Zn1-xCoxO样品.利用X射线衍射、透射电子显微镜、X射线光电子能谱以及吸收光谱对样品的结构、表面形貌、Co离子所处的价态以及光学性能进行了表征和测试.研究结果表明:所有样品都呈无规则颗粒状,样品平均粒径随Co掺杂量的增加而变小;Co离子处于+2价态,在取代Zn位;样品的结构与光学特性存在一定联系,掺Co后晶粒尺寸明显的减少与Urbach能明显的增加有关,随Co含量x的增加晶格参数增大、Co2+的d-d吸收强度增加而带隙变窄,当Co的含量x>0.03时晶胞参数转而变小、d-d吸收强度增加缓慢.通过结构与吸收的比较分析,认为掺Co样品的晶格相对于纯的ZnO膨胀可能是由于Co2+的等电子杂质效应引起晶格扭曲使晶体的无序度及缺陷密度增大造成的,x>0.03时一部分Co2+离开其四配体位产生聚集可能是造成晶胞参数下跌、d-d吸收强度变化缓慢的原因.

Comparative Study on Structure and Photoabsorption of Zn1-xCoxO

A series of Zn1-xCoxO powders were obtained by thermal decomposition of the oxalate precursors Zn1-xCox(C2O4) ·2H2O.XRD,TEM,XPS and UV-Vis-NIR absorption were employed to characterize the Co-doped ZnO powders.The results showed that Co ions were in the +2 formal oxidation states and substituted Zn in ZnO.They also suggested that structure and optical properties were interrelated.The lattice parameters(a,c),the unit cell volume(V) increased and the band gap energy Eg of Zn1-xCoxO decreased with the increasing Co concentration.The lattice parameters started to decrease,and the d-d absorption was found to increase slowly when x>0.03,which maybe due mainly to Co clusters emergence.