关于举行波兰University of Gdańsk 大学Marek Grinberg教授学术报告会的通知
报告题目：Coexistence Eu2+ and Eu3+ luminescence; two sites or single site emission?
报 告 人：Marek Grinberg（University of Gdańsk）
报告时间：2016年12月5日（星期一）20:45 ~ 21:30
报告地点：发光材料与器件国家重点实验室402
报告人简介：
Dr. Marek Grinberg is a professor of Institute of Experimental Physics in University of Gdańsk. He got his Ph.D degree in Nicholas Copernicus University in 1986. Then he became an Assistan professor in Nicholas Copernicus University from 1986 to 1997. And he became a professor in Institute of Experimental Physics of University of Gdansk from 1997 to 2006. In 2006, he is a full professor Full Professor nominated by President of Poland. He is also a reviewer of following Scientific Journals on Physics and Chemistry: Journal of Luminescence, Physical Review B, Physical Review C, Physical Review Letters, Nature , Optical Materials, Chemical Physics Letters, Chemical Physics, Radiation Measurements, Journal of Physics: Condensed Matter, Review on Advanced Materials (Russia), Journal of Noncrystalline Solids, Journal of Alloys and Compounds, Materials Chemistry and Physics, Acta Physica Polonica (Poland) , Transactions on Nuclear Science. Besides, he is a guest editor of following Scientific Journals on Physics and Chemistry: Acta Physica Polonica, Optical Materials, Radiation Measurements. Now he mainly focus on Physics of semiconductors; Optoelectronics and laser materials; Radiative and non-radiative processes in localized states in solids and High pressure spectroscopy.
报告摘要：
Depending on the treatment the one deals with Eu2+, Eu3+ or with both Eu3+ and Eu2+ luminescence. The coexistence of Eu2+ and Eu3+ luminescence in the same materials have been observed in oxyfluoride glass ceramics, borates and fluorides. In both glassy and crystalline materials Eu replaces the divalent lattice ions and Eu2+ is achieved from the reduction of Eu3+ to Eu2+. This lecture reports on the research on temperature and pressure dependence of the luminescence of the materials doped Eu. We focus on LiMgPO4 Ba2K(PO3)5, β-Ca2SiO4 and Ca3Y2(SiO4)3 doped with Eu3+ and Eu2+ . Effects of temperature and pressure on the combined Eu2+ and Eu3+ luminescence and luminescence kinetics is presented and discussed.
Under excitation with near UV light, the luminescence above phosphors is a superposition of broad band(s) in the spectral region of UV – Vis for LiMgPO4 and Vis for β-Ca2SiO4, related to the luminescence of Eu2+ ions and several sharp lines between 580 and 710 nm region, ascribed to the 5D0 → 7FJ (J = 0, 1, 2, 3 and 4) transitions in Eu3+. In the case of LiMgPO4 and Ba2K(PO3)5, intensity of the Eu2+ emission increases with increasing temperature. This is different behaviour than observed in the case of β-Ca2SiO4:Eu2+/Eu3+ where the Eu2+/Eu3+ intensity ratio has been temperature independent [1]. To explain this effect we considered that in phosphor containing europium in the Eu3+ and Eu2+ states the lowest state of europium is ground state of the Eu3+ – the 7F0 state and the ground state of the Eu2+- the 8S7/2 is one of the excited states of the system, [2]. The different temperature behaviour of the Eu emission in the investigated phosphors was related to different compensation mechanisms. The short distance compensation of the Eu3+ in the Ca2+ sites in β-Ca2SiO4:Eu2+/Eu3+, [1] and the long distance compensation of Eu3+ in the Mg2+ or Li+ sites and Eu2+ in Li+ sites in LiMgPO4:Eu2+/Eu3+. In the first case we have either Eu2+ or the Eu3+ accompanied with compensation defect. In the second case the charge state of europium ion depends on the distance from the compensation defect and temperature. The importance of the energy of the Fermi level and nature of compensation is also discusses.
References
[1] A. Baran, J. Barzowska, M. Grinberg, S. Mahlik, K. Szczodrowski , Opt. Matter. 35 (2013) 2107
[2] P. Dorenbos., Chemical Matter. 17 (2005) 6452
