Binding energies of Eu²⁺ and Eu³⁺ ions in ¦Â-Ca₂SiO₄ doped with europium

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• 作者：Anna Baran ; Justyna Barzowska ; Marek Grinberg ; Sebastian Mahlik ; Karol Szczodrowski ; Yuriy Zorenko
• 关键词：¦Â-Ca2SiO4 ; Eu3+ ; Eu2+ phosphors ; Luminescence ; Compensation mechanism ; Fermi level
• 刊名：Optical Materials
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：35
• 期：12
• 页码：2107-2114
• 全文大小：2121 K

文摘

¦Â-Ca₂SiO₄ doped with Eu²⁺and Eu³⁺was synthesized by solid state reaction. Europium replaces Ca²⁺ ions either as Eu²⁺ or Eu³⁺, both occupying two not equivalent sites; seven fold and eight fold coordinated by O^2?. ¦Â-Ca₂SiO₄:Eu²⁺, ¦Â-Ca₂SiO₄:Eu³⁺ and ¦Â-Ca₂SiO₄:Eu²⁺, Eu³⁺ samples were investigated by structural and spectroscopic methods. Specifically it has been shown that luminescence spectra of the ¦Â-Ca₂SiO₄:Eu²⁺, Eu³⁺ system were a superposition of the Eu²⁺ and Eu³⁺ emission and were independent of temperature from 18 K to ambient. To explain this effect the short distance compensation of the Eu³⁺ replacing Ca²⁺ in the ¦Â-Ca₂SiO₄ is discussed. It is argued that such compensation has to causes the conduction and valence bands bend. The existence of stable Eu²⁺ and Eu³⁺ replacing Ca²⁺ ion in lattice is discussed by consideration of the energies of the ground states of the Eu²⁺ and Eu³⁺, the Fermi energy and the energy necessary for creation of compensation defect.