主讲嘉宾：Mikhail G. Brik教授 爱沙尼亚塔尔图大学

讲座主持：王铁军 教授

讲座时间：2019年12月16日（周一）上午10:00-11:00

讲座地点：广东工业大学工学四号馆 202 会议室

嘉宾简介：

Mikhail G. Brik received his PhD from Kuban State University (Russia) in 1995 and his DSc (habilitation) from the Institute of Physics, Polish Academy of Sciences (Poland) in 2012. Since 2007 he is a professor at the Institute of Physics, University of Tartu, Estonia. Before that, he worked at Kyoto University (Japan) from 2003 to 2007, Weizmann Institute of Science (Israel) in 2002, Asmara University (Eritrea) from 2000 to 2001, and Kuban State University from 1995 to 2000. He is also a distinguished visiting professor at Chongqing University of Posts and Telecommunications (China) and Professor at Jan Długosz University (Poland). Since 2015 he serves as one of the editors of Optical Materials (Elsevier). Prof. Brik’s scientific interests cover theoretical spectroscopy of transition metal and rare earth ions in optical materials, crystal field theory, and ab initio calculations of the physical properties of pure and doped functional compounds. He is a coeditor of two books and author of 12 book chapters and about 390 papers in international journals. According to Google Scholar (November 2019), he has more than 7600 citations with h index 42. He received the Dragomir Hurmuzescu Award of Romanian Academy in 2006 and the State Prize of the Republic of Estonia in the field of exact sciences in 2013. In 2018 he received the state professor title from the President of Poland.

报告摘要:

Transition metal ions with unfilled 3d electron shell find numerous applications in optical materials, e.g. as active emitting ions in laser crystals and phosphors. In the present work we give an overview of basic electronic and spectroscopic properties of all dⁿ electron configurations (n=1...9) including the splitting of the electronic energy levels in crystal fields of various symmetries [1, 2]. Special attention is paid to the energies of the ¹E→³A₂ and ²E→⁴A₂ spin-forbidden transitions in the d², d⁸ and d³, d⁷ electron configurations, respectively [3 – 5]. The latter transition is of special importance, since it corresponds to the characteristic red emission of the Mn⁴⁺ ion that is utilized in red phosphors for the white LEDs applications.  

It has been shown that the variation of the emission wavelengths of the above-given electronic transitions is related to the degree of nephelauxetic effect experienced by the impurity ions. The Mn⁴⁺ emission is shifted towards longer wavelengths in more covalent oxide hosts and towards shorter wavelengths in more ionic fluoride materials. An empirical model has been developed to describe the observed experimental spectroscopic data. Detailed consideration of the structural arrangements of ligands around the Mn⁴⁺ ions (including the chemical bond lengths and angles between the chemical bonds) helps in understanding spectroscopic trends across the large groups of phosphor materials. Examples of combined calculations of the Mn⁴⁺ energy levels based on the crystal field theory and ab initio methods are discussed in detail. Several practical advices on how to engineer the Mn⁴⁺ red emission properties are suggested.

References

[1] Optical Properties of 3d-Ions in Crystals: Spectroscopy and Crystal Field Analysis, Editors N.M. Avram and M.G. Brik, Springer and Tsinghua University Press, 2013.

[2] M.G. Brik, A.M. Srivastava, Opt. Mater. 35 (2013) 1776-1782.

[3] M.G. Brik, A.M. Srivastava, J. Lumin. 133 (2013) 69-72.

[4] M.G. Brik, S.J. Camardello, A.M. Srivastava, ECS J. Solid State Sci. Technol. 4 (2015) R39-R43.

[5] M.G. Brik, S.J. Camardello, A.M. Srivastava, N.M. Avram, A. Suchocki, ECS J. Solid State Sci. Technol. 5 (2016) R3067-R3077.