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Hydrothermal Synthesis, Microstructure and Photoluminescence of Eu-Doped Mixed Rare Earth Nano-Orthophosphates.

Yan B, Xiao X - Nanoscale Res Lett (2010)

Bottom Line: For La(x)Gd(1-x)PO(4): Eu(3+) system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires.Similarly, Y(x)Gd(1-x)PO(4): Eu(3+), Y(0.1)Gd(0.9)PO(4): Eu(3+) and Y(0.5)Gd(0.5)PO(4): Eu(3+) samples present the pure hexagonal phase and nanorods microstructure, while Y(0.9)Gd(0.1)PO(4): Eu(3+) exhibits the tetragonal phase and nanocubic micromorphology.The photoluminescence behaviors of Eu(3+) in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, Tongji University, 200092 Shanghai, China.

ABSTRACT
Eu(3+)-doped mixed rare earth orthophosphates (rare earth = La, Y, Gd) have been prepared by hydrothermal technology, whose crystal phase and microstructure both vary with the molar ratio of the mixed rare earth ions. For La(x)Y(1-x)PO(4): Eu(3+), the ion radius distinction between the La(3+) and Y(3+) is so large that only La(0.9)Y(0.1)PO(4): Eu(3+) shows the pure monoclinic phase. For La(x)Gd(1-x)PO(4): Eu(3+) system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires. Similarly, Y(x)Gd(1-x)PO(4): Eu(3+), Y(0.1)Gd(0.9)PO(4): Eu(3+) and Y(0.5)Gd(0.5)PO(4): Eu(3+) samples present the pure hexagonal phase and nanorods microstructure, while Y(0.9)Gd(0.1)PO(4): Eu(3+) exhibits the tetragonal phase and nanocubic micromorphology. The photoluminescence behaviors of Eu(3+) in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

No MeSH data available.


The excitation (a) and emission (b) spectra of Y0.1La0.9PO4: 5 mol% Eu3+
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Figure 8: The excitation (a) and emission (b) spectra of Y0.1La0.9PO4: 5 mol% Eu3+

Mentions: The photoluminescence spectrum of Eu3+ in monoclinic phase La0.9Y0.1PO4 has also been investigated, which is shown in Fig. 8. There are no apparent excitation bands in long wavelength of 300–400 nm and the effective energy absorption takes place in the shorter wavelength of 200–280 nm, peaking at 270 nm. This broad band is ascribed to the CTB band of O2− (belonging to PO43−, here “2−” is only the formatted charge of O in PO42−) to Eu3+. At the same time, under 270 nm excitation, the emission originates mainly from those crystallographic Eu3+ sites due to the local energy transfer from Eu–O charge transfer state to the adjacent Eu3+ ions. The emission spectra are composed with the characteristic Eu3+ emission lines. Different from the luminescent spectra of YxGd1–xPO4: Eu3+ and LaxGd1–xPO4: Eu3+, the emission intensity of 5D0 → 7F2 transition for Eu3+ in La0.9Y0.1PO4 is stronger than that of 5D0 → 7F1. This result shows that more Eu3+ in the monoclinic La0.9Y0.1PO4 occupied the site with less inversion symmetry. When the Eu3+ is located at a low-symmetry local site lack of inversion center, the emission at transition is dominated in the emission spectra [41-43]. The resulting lifetime data of the selected Eu-activated rare earth orthophosphates (LaxGd1–xPO4, YxGd1–xPO4) are given in Table 1. It can be observed that the composition of hosts with different molar ratio of rare earth ions have great influence on the luminescent lifetimes of excited state of europium ions. Besides, there exists different order between LaxGd1–xPO4: Eu3+ and YxGd1–xPO4: Eu3+. For LaxGd1–xPO4: Eu3+, the luminescent lifetime reaches the longest (3.43 ms) at the x = 0.5, which is much longer than the other two compositions (x = 0.1 or 0.9), suggesting there exist a suitable molar ratio of La3+ to Gd3+ (1:1) for the luminescence of Eu3+. While it is different for YxGd1–xPO4: Eu3+, whose lifetime decreases dramatically with the increase in the molar ratio of Y, revealing the introduction of Y ion is not suitable for the luminescence of Eu3+.


Hydrothermal Synthesis, Microstructure and Photoluminescence of Eu-Doped Mixed Rare Earth Nano-Orthophosphates.

Yan B, Xiao X - Nanoscale Res Lett (2010)

The excitation (a) and emission (b) spectra of Y0.1La0.9PO4: 5 mol% Eu3+
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
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Figure 8: The excitation (a) and emission (b) spectra of Y0.1La0.9PO4: 5 mol% Eu3+
Mentions: The photoluminescence spectrum of Eu3+ in monoclinic phase La0.9Y0.1PO4 has also been investigated, which is shown in Fig. 8. There are no apparent excitation bands in long wavelength of 300–400 nm and the effective energy absorption takes place in the shorter wavelength of 200–280 nm, peaking at 270 nm. This broad band is ascribed to the CTB band of O2− (belonging to PO43−, here “2−” is only the formatted charge of O in PO42−) to Eu3+. At the same time, under 270 nm excitation, the emission originates mainly from those crystallographic Eu3+ sites due to the local energy transfer from Eu–O charge transfer state to the adjacent Eu3+ ions. The emission spectra are composed with the characteristic Eu3+ emission lines. Different from the luminescent spectra of YxGd1–xPO4: Eu3+ and LaxGd1–xPO4: Eu3+, the emission intensity of 5D0 → 7F2 transition for Eu3+ in La0.9Y0.1PO4 is stronger than that of 5D0 → 7F1. This result shows that more Eu3+ in the monoclinic La0.9Y0.1PO4 occupied the site with less inversion symmetry. When the Eu3+ is located at a low-symmetry local site lack of inversion center, the emission at transition is dominated in the emission spectra [41-43]. The resulting lifetime data of the selected Eu-activated rare earth orthophosphates (LaxGd1–xPO4, YxGd1–xPO4) are given in Table 1. It can be observed that the composition of hosts with different molar ratio of rare earth ions have great influence on the luminescent lifetimes of excited state of europium ions. Besides, there exists different order between LaxGd1–xPO4: Eu3+ and YxGd1–xPO4: Eu3+. For LaxGd1–xPO4: Eu3+, the luminescent lifetime reaches the longest (3.43 ms) at the x = 0.5, which is much longer than the other two compositions (x = 0.1 or 0.9), suggesting there exist a suitable molar ratio of La3+ to Gd3+ (1:1) for the luminescence of Eu3+. While it is different for YxGd1–xPO4: Eu3+, whose lifetime decreases dramatically with the increase in the molar ratio of Y, revealing the introduction of Y ion is not suitable for the luminescence of Eu3+.

Bottom Line: For La(x)Gd(1-x)PO(4): Eu(3+) system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires.Similarly, Y(x)Gd(1-x)PO(4): Eu(3+), Y(0.1)Gd(0.9)PO(4): Eu(3+) and Y(0.5)Gd(0.5)PO(4): Eu(3+) samples present the pure hexagonal phase and nanorods microstructure, while Y(0.9)Gd(0.1)PO(4): Eu(3+) exhibits the tetragonal phase and nanocubic micromorphology.The photoluminescence behaviors of Eu(3+) in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, Tongji University, 200092 Shanghai, China.

ABSTRACT
Eu(3+)-doped mixed rare earth orthophosphates (rare earth = La, Y, Gd) have been prepared by hydrothermal technology, whose crystal phase and microstructure both vary with the molar ratio of the mixed rare earth ions. For La(x)Y(1-x)PO(4): Eu(3+), the ion radius distinction between the La(3+) and Y(3+) is so large that only La(0.9)Y(0.1)PO(4): Eu(3+) shows the pure monoclinic phase. For La(x)Gd(1-x)PO(4): Eu(3+) system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires. Similarly, Y(x)Gd(1-x)PO(4): Eu(3+), Y(0.1)Gd(0.9)PO(4): Eu(3+) and Y(0.5)Gd(0.5)PO(4): Eu(3+) samples present the pure hexagonal phase and nanorods microstructure, while Y(0.9)Gd(0.1)PO(4): Eu(3+) exhibits the tetragonal phase and nanocubic micromorphology. The photoluminescence behaviors of Eu(3+) in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

No MeSH data available.