Interstitial Site Engineering for Creating Unusual Red Emission in La₃Si₆N₁₁:Ce³⁺

Abstract

Traditionally, phosphors are developed by doping activators on standard crystallographic sites of selected inorganic hosts, thus enabling the prediction of their luminescence with some empirical models or theoretical calculations. Here, we propose the idea of interstitial site engineering as a totally different way to design phosphors with promising properties. In detail, a red-emitting phosphor La3Si6N11:Ce3+,Al3+ was developed by engineering the interstitial Ce3+ site, which produces an unusual red emission band (λem = 600–665 nm) under blue light excitation. The origin of this red emission was assigned from the first-principle calculation to the Ce3+ ion occupying the [Si8N8] void in the c∼1/2 layer of which the calculated transition energies matching with experiment within 0.1 eV. Such an interstitial Ce3+ site was created as a charge compensator for the aliovalent substitution of Si4+ by Al3+ ions. The red-enhanced La3Si6N11:Ce3+,Al3+ phosphor showed great potentials for improving the optical quality (i.e., color temperature and color rendition) of laser-driven white light. This work indicates that the interstitial site engineering is an efficient way for generating new luminescence centers and opens up an avenue for designing phosphors with appealing properties.

Learning from Mineral Structures toward New Luminescence Materials for Light-Emitting Diode Applications

“…In the recent study, Xie's group also developed a red-emitting phosphor La 3 Si 6 N 11 : Ce 3+ , Al 3+ with promising properties by aliovalent substitution of Si 4+ by Al 3+ ions. 73 When the Al 3+ ions are incorporated into the Si 4+ crystallographic site of the host structure, Ce 3+ as an interstitial ion prefers to occupy the void of the [Si 8 N 8 ] ring (Figure 7e) in La 3 Si 6 N 11 for the charge compensation that causes the aliovalent substitution. As a result, these La 3 Si 6 N 11 :Ce 3+ , Al 3+ phosphors display an unusual red emission band centering at 600−665 nm with different Al 3+ concentrations (Figure 7f) and show great potential for improving the optical quality.…”

“…As a result, these La 3 Si 6 N 11 :Ce 3+ , Al 3+ phosphors display an unusual red emission band centering at 600−665 nm with different Al 3+ concentrations (Figure 7f) and show great potential for improving the optical quality. 73 To sum up, heterovalent (including aliovalent) substitution certainly will cause charge imbalance and give rise to various charge compensation mechanisms. To give a sharp insight into the connection between these mechanisms and local structure as well as luminescence properties can arouse many other inspirations to design new phosphor materials.…”

Structural Engineering of Eu2+-Doped Silicates Phosphors for LED Applications

“…Moreover, our group developed a general heterovalent substitution strategy by Ln 3+ (Ln = Gd, Tb, Dy, Tm, Yb, and Lu) substituting Hf 4+ in K 2 HfSi 3 O 9 :Eu 2+ and realized the results of “kill three birds with one stone” with controllable emission properties, improved thermal stability and high quantum efficiency . Recently, Xie’s group also discovered an unusual red emission in La 3 Si 6 N 11 :Ce 3+ via the heterovalent substitution of Si 4+ by Al 3+ ions to create an interstitial Ce 3+ site . Hence, the heterovalent substitution strategy can really open a new avenue for the PL tuning.…”

Development of sialon phosphors and their applications to solid-state lighting

“…These include AlN:Eu 2+ , 43),44) ¢-sialon;Eu 2+ , 26),45), 46) (La,Ca) 3 Si 6 N 11 :Eu 2+ , 47) and La 3 (Si,Al) 6 N 11 :Ce 3+ . 48) The position of Eu 2+ in ¢-sialon remained a miracle until Kimoto et al directly observed it by using high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). 45) As seen in Figs.…”

“…Xie et al observed a large redshift in Al-doped La 3 Si 6 N 11 :Ce 3+ , producing a broadband red phosphor ( em = 665 nm, fwhm ³200 nm). 48) With aids of the first principles calculations, the red emission can be ascribed to that Ce 3+ occupies the interstitial sites (i.e., [Si8N8] voids) newly formed as a charge compensator for the aliovalent substitution of Si 4+ by Al 3+ .…”