高压下缺陷对锐钛矿相TiO_(2)多晶电输运性能的影响:交流阻抗测量  

Effects of defects on electrical transport properties of anatase TiO_(2)polycrystalline under high pressure:AC impedance measurement

作　　者：王月[1] 邵渤淮 陈双龙[1] 王春杰[1] 高春晓[2] Wang Yue;Shao Bo-Huai;Chen Shuang-Long;Wang Chun-Jie;Gao Chun-Xiao(College of Physical Science and Technology,Bohai University,Jinzhou 121013,China;State Key Laboratory of Superhard Materials,Jilin University,Changchun 130012,China)

机构地区：[1]渤海大学物理科学与技术学院,锦州121013 [2]吉林大学,超硬材料国家重点实验室,长春130012

出　　处：《物理学报》2023年第12期223-232,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12004050);辽宁省教育厅项目(批准号:LJKMZ20221493)资助的课题。

摘　　要：采用高压原位阻抗谱测量技术对锐钛矿Ti O_(2)多晶的电输运性质进行了系统研究.在6.4,11.5和24.6 GPa压力处发现了晶粒和晶界的电阻、参数因子和弛豫频率的反常变化行为.研究分析表明:6.4和11.5 GPa压力点分别对应着Ti O_(2)由锐钛矿转变为a-Pb O_(2),再转变为斜锆石的结构相变,当压力高于24.6 GPa时,Ti O_(2)完全转变为斜锆石相.通过分析晶粒和晶界电阻在压力作用下的变化行为可知,本征缺陷的存在对Ti O_(2)高压下电输运性质的变化起着关键的作用.在6.4 GPa压力处,相变的发生导致缺陷的作用发生了变化,由作为复合中心的深能级缺陷转变为向导带和价带提供载流子的浅能级缺陷,并且作为浅能级缺陷存在至实验最高压力点38.9 GPa,浅能级缺陷在能带中的位置也随着相变发生而改变.晶粒和晶界的激活能随着压力升高而降低,表明高压下载流子在晶粒和晶界的输运变得更加容易.此外,Ti O_(2)晶粒和晶界的弛豫频率比值随压力的升高而不断减小,高压下的晶界效应不明显.The electrical transport properties of anatase TiO_(2)polycrystalline have been systematically investigated by using high pressure in-situ impedance spectroscopy measurements.The anomalous behaviors of resistance,parameter factor and relaxation frequency of grain and grain boundary can be found at 6.4,11.5 and 24.6 GPa.The results indicate that the first two discontinuous points(6.4 and 11.5 GPa)correspond to the phase transitions of TiO_(2)from anatase to a-PbO_(2)and then to baddeleyite,respectively.Above 24.6 GPa,TiO_(2)completely transforms into the baddeleyite phase.Based on the change of grain resistance and grain boundary resistance under pressure,intrinsic defects play a crucial effect in the electrical transport properties of TiO_(2)at high pressures.At 6.4 GPa,the occurrence of phase transition gives rise to the variation of defects’role,from a deep energy level defect(as a recombination centre)changes into a shallow energy level defect(providing carriers for the conduction and valence bands).In addition,the position of defect in energy band changes with pressure increasing.The phase transition of TiO_(2)at 6.4 GPa is the rearrangement of TiO6 octahedron,while the other one at 11.5 GPa can be attributed to the migration of oxygen Schottky defects from inner to surface.Combining the packing factor and relaxation frequency,the electrical transport properties of TiO_(2)under pressure are revealed,the packing factor and the relaxation frequency are closely related to the mobility and the carrier concentration,respectively.The activation energy of grain and grain boundary decrease with the pressure elevating,indicating that the transport of carriers in grain and grain boundary become easier under pressure,and the former is smoother than the latter owing to the activation energy of grain being smaller than that of grain boundary in the same pressure range.Moreover,the relaxation frequency ratio of TiO_(2)grain and TiO_(2)grain boundary decreases with pressure increasing,and the grain boundary effect under h

关 键 词：高压 TiO_(2) 缺陷 晶界 

分 类 号：O469[理学—凝聚态物理] TQ134.11[理学—电子物理学]