Full
GAO Mingyuan (1998-), male, Master candidate. E-mail: 1206861141@qq.com
Outline
(Ba1-xMex)1.95SiO4:0.05Eu (Me=Ca, Mg) phosphor was synthesized in a reducing atmosphere by a high-temperature solid-phase method. Ca2+ and Mg2+ solubilities in Ba2SiO4-phase should be 10% (mole fraction, the same below) and 30%, and the solid solution induces an increase in green fluorescence brightness under ultraviolet excitation. The intensity of (Ba0.9Ca0.1)1.95SiO4:0.05Eu and (Ba0.7Mg0.3)1.95SiO4:0.05Eu phosphors is 110% and 140% greater than that of Ba2SiO4:Eu under 365 nm, and 105% and 125% greater than that of Ba2SiO4:Eu under 254 nm. Based on the analysis by X-ray diffraction, (Ba1-xCax)1.95SiO4 (0.1<x≤0.3) is T-phase but not Ba2SiO4-phase. Ca2+ or Mg2+ substitution does not decrease in cell volume but causes the better crystallization (i.e., the diffraction peak is higher, and the half-width is more narrow). Further more, b decreases a little more quickly than c, indicating that Eu2+ ions prefer 9-coordinated Ba2+(II) sites more than 10-coordinated Ba2+(I) sites. According to the high-resolution photo luminescent spectra, Eu2+(I) contributes more than Eu2+(II) for the green luminescence intensity. Moreover, Eu2+(I)/Eu2+(II) ratio increases as Ca2+ or Mg2+ solubility increases. The high-resolution X-ray photoelectron spectra of Eu4d indicate that the valence of Eu is rarely changed after cation substitution. Ca2+ or Mg2+ substitution can improve the crystallinity, promote Eu2+ to enter Ba2+(I) site(which would has higher luminescent efficiency) and keep Eu ion valence stable due to the improvement of phosphor luminescent intensity by cation substitution.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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