Ti1－xCrxO2±δ体系的相关系、晶体结构和磁性能研究

采用溶胶凝胶法制备了Ti_1-xCr_xO_2±δ体系系列样品.利用扫描电子显微镜(SEM)，X射线光电子能谱(XPS)，粉末X射线衍射分析(XRD)方法研究了Ti_1-xCr_xO_2±δ系列样品的颗粒尺寸、形貌、组分化学态、相关系和固溶区范围；并利用超导量子干涉磁强计对样品的磁性能进行了研究.采用Rietveld结构精修的方法研究了Cr的不同掺杂量对TiO₂晶体结构的影响，研究表明，1000℃烧结的样品的固溶区范围是x=0—0.03，为金红石单相；随着Cr掺杂量的增加，金红石相晶胞参数规律性地减小；当x>0.03，为金红石相和CrO₂相两相共存.综合XRD和磁性测量结果，500℃烧结的样品的固溶区范围是x=0—0.02，为锐钛矿单相；随着Cr掺杂量的增加，锐钛矿相晶胞参数规律性地减小；当x≥0.04，为锐钛矿相和绿铬矿相(Cr₂O₃)两相共存.XPS实验结果表明，500℃和1000℃退火的样品中Cr都是以Cr⁺³和Cr⁺⁶两种化学态存在，1000℃烧结的样品中可能有更多的Cr³⁺转化为Cr⁶⁺.根据M-H和M-T曲线的测试结果发现，本文500℃烧结的Ti_1-xCr_xO_2±δ体系样品当x=0—0.02时，为室温铁磁性.当x≥0.04时，由铁磁相和顺磁相所组成，在低温下有较强的铁磁性；室温下主要是顺磁相，铁磁相只占据很小的体积分数. 关键词： 1-xCr_xO_2±δ体系')" href="#">Ti_1-xCr_xO_2±δ体系 相关系 固溶区 磁性能

Study on phase relations, crystal structure and magnetic properties of Ti1－xCrxO2±δ system

A series of samples of Ti_1-xCr_xO_2±δ were prepared by Sol-Gel process. The particle size, morphology, valence, solid solution range, phase relations and magnetic properties of Ti_1-xCr_xO_2±δ samples were studied by XRD, SEM, XPS and SQUID measurements. Meanwhile, the Rietveld refinement method was employed to study the effect of Cr doping on the crystal structure ofTiO₂. The results show that the solid solution range of both Ti_1-xCr_xO_2±δ systems annealed at 1000℃ are x＝0—0.03. Their lattice parameters decrease with increasing Cr concentration. The results of both XRD analysis and magnetic measurements show that the solid solution range of both Ti_1-xCr_xO_2±δ systems annealed at 1000℃ are x＝0—0.02. Cr ions of samples sintered at 500℃ and 1000℃ have two chemical states, Cr⁺³ and Cr⁺⁶， respectively, while the samples　sintered at 1000℃ have much greater Cr⁺⁶ content than the ones at 500℃. According to the results of M-H and M-T measurements, magnetic properties of Ti_1-xCr_xO_2±δ samples sintered at 500 ℃ with x=0—0.02 are ferromagnetic. When x≥0.04, they consisted of both ferromagnetic phase and paramagnetic phase. They have stronger ferromagnetic properties at low temperature (50K). The paramagnetic phase is the main constituent and the ferromagnetic phase has less volume fraction at room temperature.