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

Abstract

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. Ba1−x Eu x SiN2 (0 < x ≤ 0.1) shows a broad emission band in the wavelength range of 500–750 nm with maxima from about 600 to 630 nm with increaseing Eu2+ concentration, while Sr1−x Eu x SiN2 (0 < x ≤ 0.1) shows a broad emission band in the wavelength range of 550–850 nm with maxima from 670 to 685 nm with increasing Eu2+ concentration. The high absorption and strong excitation bands of M1−x Eu x SiN2 (0 < x ≤ 0.1; M = Sr, Ba) in the wavelength range of 300–530 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 400–700 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.

Structure, composition, morphology, photoluminescence and cathodoluminescence properties of ZnGeN2 and ZnGeN2:Mn2+ for field emission displays

“…The surrounding ligand in ZnGeN 2 is N 3À with an electronegativity of 3.04 (Pauling scale), <3.44 for O 2À in oxide compounds. This leads to the increase in the covalent interaction (the nephelauxetic effect) between Mn 2+ and the surrounding tetrahedrally coordinated nitrogen and finally contributes to a stronger crystal field in nitrides than oxides [31,32].…”

Highly efficient non-rare-earth red emitting phosphor for warm white light-emitting diodes

“…This difficulty can be completely overcome by adding a suitable red phosphor in LEDs to complement the red light component. To this end, great efforts have been made to exploit novel rare-earthdoped red phosphors, and the most successful materials are Eu 2 þ -or Ce 3 þ -doped (oxy)nitride compounds [14][15][16][17][18][19] , typically CaAlSiN 3 :Eu 2 þ (ref . 20).…”

Inorganic Phosphor Materials for Lighting

“…Although YAG and other garnet-type host lattices continue to be considered very promising materials, it should be noted that a variety of other classes of phosphors have been developed and are now attracting increased attention. Examples of such are silicates [189], nitrides [190][191][192], and oxy-nitrides [193,194], to name a few.…”