In this study, the conventional mineralogical tests, LA-ICP-MS and photoluminescence spectroscopy (PL spectroscopy) tests were carried out on the scheelite in the Xuebaoding area (Pukouliang, Sandaoqi, Shuijingzhen, Wuzhutang) of Sichuan Province, China, aiming to obtain its chemical compositions, and mineralogy and luminescence characteristics. The CaWO4 polycrystals doped with different proportions of Sm, Eu and Dy elements were synthesized by high temperature solid phase method, and their photoluminescence spectra were analyzed to explore the effects of Sm, Eu and Dy elements on their red fluorescence. The results showed that under the irradiation of medium-wave ultraviolet light (310 nm), the fluorescence colour of the scheelite samples from Xuebaoding area of Sichuan is divided into red and light-yellow. The chemical composition test results showed that the samples contain trace elements such as Sr, Nb, Mn, Mo, and rare earth elements (REE). The overall content of REE (335.8-2 243.0 μg/g) and Sr element (126.3-5 188.2 μg/g) is high. The Nb, Mn, and Mo elements enriched in the yellowish fluorescence region indicate that Mn, Mo, and Nb in the scheelite can increase the fluorescence emission intensity of the trivalent rare earth ion (RE3+) as an activator.The PL spectra showed that the red fluorescence is mainly contributed by Sm3+ and Eu3+, following by Dy3+, Tb3+ and Pr3+. The light-yellow fluorescence is mainly caused by Dy3+, following by Sm3+ and Eu3+. By analyzing the PL spectra of synthetic scheelite, it was concluded that Dy3+ is a sensitizer for Sm3+ and Eu3+, and Dy3+ enhances the fluorescence emission intensity of Sm3+ more obviously, especially the 4G5/2→ 6H7/2 transition (580-620 nm) of Sm3+.In the natural scheelite, Dy3+ hinders the energy transfer of Sm3+→Eu3+ and the strongest emission peak of Sm3+ in some samples changes from 4G5/2→ 6H9/2 transition (630-660 nm) to 4G5/2→ 6H7/2 transition (580-620 nm).
Figure
1.
The scheelites sample from Xuebaoding, Sichuan Province (a) and their fluorescence under medium wave (310 nm) ultraviolet light (b) (Note: The scale of the sample picture is not uniform)
Figure
2.
The element content distribution of Nb(a), Mn(b), Mo(c) and Sr (d) in the light-yellow and red fluorescence regions of the scheelite samples from Xuebaoding, Sichuan Province
Figure
8.
The PL spectra of CaWO4 polycrystalline samples and the relationship between the peak intensity ratio of the strongest emission peaks of Sm3+ and Eu3+ and the content of Eu3+ and Dy3+ are shown: (a) PL spectra of Ca0.9-xWO4∶Sm0.13+, Eux3+ (x=0.000 2, 0.000 4, 0.000 6, 0.000 8, 0.001 0); (b) The peak intensity ratio of the strongest emission peaks of Sm3+ (646 nm) and Eu3+ (615 nm) varies with the content of Eu3+; (c) PL spectra of Ca0.899-xWO4∶Sm0.13+, Eu0.0013+, Dyx3+(x=0.005, 0.010, 0.015); (d) The peak intensity ratio of the strongest emission peaks of Sm3+ (646 nm) and Eu3+ (615 nm) and the peak intensity ratio of the emission peaks of Sm3+ (646 nm) and Sm3+ (600 nm) change with the content of Dy3+
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