fig6

Figure 6. (A) Photoluminescence of the Li_xNbO₃:1mol%Pr³⁺ sample^[64]. Reproduced from Ref.^[64] with permission from the Elsevier; (B) Spin-polarized partial density of states and Bader charges for bulk LiNbO₃ and the sample doped with $$ \mathrm{Pr}_{\mathrm{Li}}^{2+} $$ 2$$ \mathrm{V}_{\mathrm{Li}}^{-} $$ and $$ \mathrm{Pr}_{\mathrm{Nb}}^{2-} $$ +$$ \mathrm{V}_{\mathrm{O}}^{2+} $$ defects^[107]. Reproduced from Ref.^[107] with permission from the Elsevier; (C) Afterglow curves of the LiNbO₃:Pr³⁺/xMg²⁺ samples, with the fitting result of LiNbO₃:Pr³⁺/6%Mg²⁺ shown in the inset^[29]. Reproduced from Ref.^[29] with permission from the Elsevier; (D) PersL decay curves for LiNbO₃:Pr³⁺/Mg²⁺ and LiNbO₃:Pr³⁺ excited by the UV LED (365-370 nm, 60 s), with photographs of LiNbO₃:Pr³⁺/Mg²⁺ shot in a dark room shown in the inset^[27]. Reproduced from Ref.^[11] with permission from the Royal Society of Chemistry; (E) Schematic mechanism of photocatalytic nitrogen fixation over LiNbO₃:Pr^3+[108]. Reproduced from Ref.^[108] with permission from the Springer Nature. PLN: LiNbO₃: Pr³⁺; MPLN: LiNbO₃: Pr³⁺, Mg²⁺; NHE: normal hydrogen electrode; PersL: persistent luminescence; Pr: praseodymium; UV: ultraviolet; LED: light-emitting diode.