Preparation, Electronic Structure, and Photoluminescence Properties of Eu2+- and Ce3+/Li+-Activated Alkaline Earth Silicon Nitride MSiN2 (M = Sr, Ba)

详细信息    查看全文

• 作者：C. J. Duan ; X. J. Wang ; W. M. Otten ; A. C. A. Delsing ; J. T. Zhao ; H. T. Hintzen
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：February 26, 2008
• 年：2008
• 卷：20
• 期：4
• 页码：1597 - 1605
• 全文大小：245K
• 年卷期：v.20,no.4(February 26, 2008)
• ISSN：1520-5002

文摘

The electronic structure of alkaline-earth silicon nitride MSiN₂ (M = Sr, Ba) was calculated using the CASTEP code. BaSiN₂ is calculated to be an intermediate band gap semiconductor with a direct energy gap of about 2.9 eV, while SrSiN₂ is an intermediate band gap semiconductor with an indirect energy gap of about 3.0 eV. As expected, the calculated optical band gaps of MSiN₂ (M = Ba, Sr) are lower compared to the experimentally determined values (about 4.1 eV for BaSiN₂ and 4.2 eV for SrSiN₂). In addition, the luminescence properties of Eu²⁺ and Ce³⁺ in MSiN₂ (M = Sr, Ba) have been studied. Ba_1−xEu_xSiN₂ (0 < x ≤ 0.1) shows a broad emission band in the wavelength range of 500&ndash;750 nm with maxima from about 600 to 630 nm with increaseing Eu²⁺ concentration, while Sr_1−xEu_xSiN₂ (0 < x ≤ 0.1) shows a broad emission band in the wavelength range of 550&ndash;850 nm with maxima from 670 to 685 nm with increasing Eu²⁺ concentration. The high absorption and strong excitation bands of M_1−xEu_xSiN₂ (0 < x ≤ 0.1; M = Sr, Ba) in the wavelength range of 300&ndash;530 m are very favorable properties for application as light-emitting-diode conversion phosphors. Ce³⁺- and Li⁺- codoped MSiN₂ (M = Sr, Ba) exhibits a broad emission band in the wavelength range of 400&ndash;700 nm with a peak center at about 485 nm for BaSiN₂ and about 535 nm for SrSiN₂. A comparison is made between the luminescence properties of Eu²⁺ and Ce³⁺ in the Sr versus Ba compounds. The long-wavelength excitation and emission of Eu²⁺ and Ce³⁺ ions in the host of MSiN₂ (M = Sr, Ba) are attributed to the effect of a high covalency and a large crystal field splitting on the 5d bands of Eu²⁺ and Ce³⁺ in the nitrogen coordination environment.