烧绿石型氧化物Dy_(2)Ti_(2)O_(7)的电弧熔炼制备与性能研究  

Arc-melting synthesis and physical properties of pyrochlore-type oxide Dy_(2)Ti_(2)O_(7)

作　　者：姚金雷 彭宇星 YAO Jinlei;PENG Yuxing(School of Physical Science and Technology,SUST,Suzhou 215009,China;Key Laboratory of Efficient Low-carbon Energy Conversion and Utilization of Jiangsu Provincial Higher Education Institutions,SUST,Suzhou 215009,China)

机构地区：[1]苏州科技大学物理科学与技术学院,江苏苏州215009 [2]苏州科技大学江苏省高校低碳能源高效转化与利用重点实验室,江苏苏州215009

出　　处：《苏州科技大学学报（自然科学版）》2024年第4期84-92,138,共10页Journal of Suzhou University of Science and Technology（Natural Science Edition）

基　　金：国家自然科学基金项目(21771136);苏州科技大学研究生优质资源建设项目(23SZKC-03)。

摘　　要：通过电弧熔炼制备高密度缺陷的Dy_(2)Ti_(2)O_(7),呈黑色,为立方晶系的烧绿石结构(空间群Fd-3m,No.227),晶格常量a=1.01333(3)nm。产生10.7%的阳离子反占位Ti_(Dy)、钛离子空位V_(Ti)等高密度位错,[DyO_(8)]的立方配位体畸变度变小而[TiO_(6)]八面体畸变增强,诱导出在139 cm^(-1)处的新拉曼峰。禁带宽度为E_(g)=3.5 eV,较常规样品的Eg~3.8 eV降低了0.3 eV左右。在1.0~3.4 eV之间,光谱存在一个宽的吸收峰,由Dy^(3+)的4f能级之间的跃迁引起。由于贫Dy的存在,2 K下高场诱发磁矩为4.8μ_(B)/Dy,稍低于常规样品的~5.0μB/Dy,加快了16 K附近Dy^(3+)的单离子自旋翻转过程。电阻测试表明Dy_(2)Ti_(2)O_(7)符合半导体行为,热激活能为E_(a)=346.9 meV。The Dy_(2)Ti_(2)O_(7) oxide with high-density defects has been prepared by arc melting,showing a metallic black,which crystallizes in a cubic pyrochlore structure(space group Fd-3m,No.227)with a lattice parameter a=1.01333(3)nm.There exist high-density defects,such as the cation anti-site occupation Ti_(Dy) with the occu-pancy of 10.7%and titanium vacancies V_(Ti).The distortion of[DyO_(8)]cubic coordination is weakened and the dis-tortion of[TiO_(6)]octahedron is enhanced,resulting in a new Raman peak at 139 cm-1.Its band gap is as large as E_(g)=3.50 eV,smaller by~0.3 eV than Eg~3.8 eV of the conventional samples.In the range of 1.0~3.4 eV,the transition between the 4f levels of Dy^(3+)results in a broad light absorption peak.Due to the presence of Dy-poor characteristic,the spontaneous magnetic moment of Dy_(2)Ti_(2)O_(7) is as large as 4.8μB/Dy at 2 K which is somewhat smaller than~5.0μ_(B)/Dy of the conventional samples,accelerating the flipping process of Dy^(3+)spins near 16 K.The resistivity measurement shows that Dy_(2)Ti_(2)O_(7) is a semiconductor with the thermal activation energy E_(a)=346.9 meV.

关 键 词：烧绿石 电弧熔炼 高密度缺陷 结构畸变 

分 类 号：O469[理学—凝聚态物理]