Investigation of 4f‐Related Electronic Transitions of Rare‐Earth Doped ZnO Luminescent Materials: Insights from First‐Principles Calculations

Abstract

Rare‐earth (RE) doped zinc oxides (ZnO) are regarded as promising materials for application in versatile color‐tuned devices. However, the understanding of underlying luminescence mechanism and the rule of 4 f‐related electronic transition is still limited, which is full of significance for the exploration of advanced RE‐based ZnO phosphors. Thus, a series of ZnO : RE (RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb) phosphors have been investigated by means of first‐principles calculations. Meanwhile, we also consider the effect of native defects (VO, VZn) on the luminescence of ZnO : RE phosphors. Accordingly, four types of electric‐dipole allowed transition processes are figured out in ZnO : RE family. Additionally, we manifest that the VO can further improve the luminescent performance of ZnO : RE phosphors, and give insightful guidance to design desired RE‐based ZnO materials with excellent luminescence.

Effect of Doping TiO2 NPs with Lanthanides (La, Ce and Eu) on the Adsorption and Photodegradation of Cyanide—A Comparative Study

“…As a result, TiO 2 microcrystals with different sizes and random orientations can be formed [ 81 ]. The results of this study agree with those reported by other authors, who have shown that doping enables stabilization of small particles [ 76 ]. Regarding EDS analysis, the results obtained allowed us to confirm the presence of La (1.32 wt%), Ce (1.34 wt%), and Eu (1.28 wt%) on the TiO 2 structure.…”

“…The results depicted in Figure 1 indicate that doping with lanthanide (Ln) can impact the crystal structure of pure TiO 2 (anatase), causing slight broadening and reduction in intensity of its characteristic diffraction peaks. This suggests that the adsorbent and photocatalytic properties of this semiconductor oxide can be affected by the presence of Ln dopants [ 76 ]. According to the literature, it is very difficult for lanthanide ions to substitute Ti 4+ ions in the TiO 2 crystal lattice.…”

Comparative Study of the Effect of Doping ZnTiO3 with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems

“…Figure 1 shows that the doping of La and Ce ions decreases the intensity of the ZnTiO 3 peaks, demonstrating that both dopants have a significant influence on its crystalline structure, which will definitely influence the adsorbent and photocatalytic activity of this semiconductor [ 74 ]. It is widely known that the ionic radii of La 3+ (0.113 nm), Ce 3+ (0.111 nm), and Ce 4+ (0.101 nm) are much larger than those of Ti 4+ (0.068 nm), so it is very difficult for these lanthanide ions to replace the Ti 4+ in the ZnTiO 3 crystal lattice.…”

“…As shown in this figure, the La/ZTO and Ce/ZTO nanoparticles are smaller than ZTO nanoparticles. According to the literature, this is because the dispersion of the La 3+ and Ce 3+/4+ doping ions on the surface of the ZTO crystallites restricts direct contact with neighboring crystallites, which inhibits their growth and stabilizes the smaller particles [ 74 ]. These changes are in agreement with the results deduced from the XRD patterns that confirm the incorporation of heterogeneous elements on the semiconductor surface.…”

Cerium-, Europium- and Erbium-Modified ZnO and ZrO2 for Photocatalytic Water Treatment Applications: A Review

“…At this regard, Elias et al [90,91] and Ha et al [84] have stated that the insertion of cerium atoms inside the crystallographic environment of ZnO can reached up to 5 mole% of the rare-earth element. As suggested by DFT calculations, the insertion of Ce into the ZnO lattice is energetically stable, affecting the crystal size, lattice strain, bond length and lattice parameters with respect to bare ZnO [97]. In addition to the alteration of the lattice parameters, the insertion of Ce 4+ would also increase the number of intrinsic defects in zinc oxide due to charge compensation, especially generating oxygen vacancies (V O ) [98].…”