Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Phys Chem Chem Phys. 2012 Aug 7;14(29):10160-7. doi: 10.1039/c2cp41044c. Epub 2012 Jun 21.
The role of acceptor dopants (S and Se) in controlling the ionic conductivity of single crystal TlBr, grown by the vertical Bridgman method, was examined as a function of temperature with the aid of impedance spectroscopy. Several features in the conductivity were identified and related to acceptor dopant-Br vacancy association, acceptor dopant exsolution, and Br vacancy mobility. The corresponding enthalpies for these processes were extracted from the data and were found to be equal to H(a) = 0.42 ± 0.07 eV, H(sol) = 1.55 ± 0.18 eV and H(m,Br) = 0.31 ± 0.02 eV respectively, the latter consistent with earlier studies on donor doped and undoped TlBr. A long term conductivity decay in the extrinsic region, attributed to S or Se exsolution, was observed. The time constant associated with exsolution was found to be thermally activated with an activation energy of 0.47 ± 0.1 eV. Estimates for Se solubility at different temperatures are provided.
采用垂直布里奇曼法生长的 TlBr 单晶，我们借助阻抗谱研究了受主掺杂剂（S 和 Se）在控制其离子电导率方面的作用随温度的变化。我们确定了电导率的几个特征，并将其与受主掺杂剂-Br 空位缔合、受主掺杂剂的离析以及 Br 空位迁移率相关联。从数据中提取出这些过程的相应焓，并发现它们分别等于 H(a) = 0.42 ± 0.07 eV、H(sol) = 1.55 ± 0.18 eV 和 H(m,Br) = 0.31 ± 0.02 eV，后者与先前对施主掺杂和未掺杂 TlBr 的研究一致。我们观察到在本征区的长期电导率衰减归因于 S 或 Se 的离析。发现与离析相关的时间常数是热激活的，其激活能为 0.47 ± 0.1 eV。提供了不同温度下 Se 溶解度的估计值。
