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18 results on '"Feng, Qingrong"'

2. Low-temperature sintering to fabricate MgB2 by using Mg(BH4)2 as precursor.

Author

Huang, Zigeng, Cai, Xinwei, Xi, Dan, Luo, Wenhao, Guo, Chen, Feng, Qingrong, Nie, Ruijuan, Wang, Furen, and Gan, Zizhao

Subjects
SINTERING, CRITICAL currents, FLUX pinning, GRAIN size, MAGNETIC fields, BALL mills
Abstract

Low-temperature sintering to fabricate MgB2 is considered a promising method because it reduces the formation of MgO and reduces the grain size, thereby increasing the critical current density. Chemical doping, ball milling of precursor and modifying the Mg source in precursor for low-temperature sintering have all been carefully investigated. However, the threshold of sintering temperature have been kept near 500 °C. A new in-situ method to low-temperature sintering using Mg(BH4)2 as a precursor is presented in this paper. Mg(BH4)2 decomposes into highly reactive nanoscale Mg and B in a molar ratio of 1:2 without impurities. In this method, only 2 h of sintering at 400 °C is required to completely react Mg with B to produce MgB2, and after 54 h sintering, the sample has comparable JC to the normal MgB2 from solid-state reaction method sintered at 800 °C. The sample sintered at 500 °C give better JC than normal MgB2 under both high and low magnetic field. [ABSTRACT FROM AUTHOR]

Published
2021
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6. Ge Film Contacts to Radio Frequency Sputtered Y-Ba-Cu-O Superconductor Film

Author

Feng Qingrong, Tong Litai, Chen Hai-Ying, Wang Gui-Zhi, Dai Yuandong, Qian Yi, Qiao Yong-Ping, Zhang Bei, Liu Zun-Xiao, Lan Jian, and Xing Miaoxiang

Subjects
Superconductivity, Materials science, business.industry, Contact system, General Physics and Astronomy, Optoelectronics, Radio frequency, Crystallite, business, Epitaxy, Layer (electronics), Deposition (law)
Abstract

The semiconductor-superconductor contact system of Ge/Y-Ba-Cu-O (YBCO)/SrTiO3 has been successfully fabricated by two steps of deposition. The YBCO film in the contact of Ge/YBCO did not lose its superconductivity and its Tc (on set) did not degrade as well. The top layer of Ge was polycrystalline with preferred orientation corresponding to the epitaxial structure of the underlayer of YBCO.

Published
1991

8. Thermally Activated Flux Motion in 2223 Phase High Temperature Superconductors

Author

Feng Xiaoqi, Feng Qingrong, Zhang Han, Li Chuan-Yi, Chen Jun, Yin Dao-Le, Li Gang, and Zhu Xing

Subjects
High-temperature superconductivity, Materials science, Secondary phase, Condensed matter physics, Volume (thermodynamics), law, Phase (matter), General Physics and Astronomy, Thermodynamics, Flux motion, Scaling, Isothermal process, law.invention
Abstract

Isothermal V-I characteristics of Bi1.8Pb0.2Sr2Ca2Cu3Oy high temperature superconductors (HTSCs) have been systematically studied. Below the irreversibility temperature Tr(H), two important features were observed: 1) Both positive and negative curvatures can coexist in the same isothermal V-I curve, so it is different from the scaling behavior V ∝ exp(-(J0/J)μ). 2) The activation volume of flux motion is found temperature dependent as (1-T/Tr(H))-2ν with ν about 0.5. This behavior supports the existence of a two-dimensional secondary phase transition below Hc2(T) in this Bi-based HTSCs.

Published
1992

17. Superconductivity of (Tl 1-x Al x ) 2 Ba 2 Ca 2 Cu 3 O y

Author

Shen Zhaohui, Wei Chongde, Lin Qin, Feng Qingrong, Xue Lixin, Gan Zi-Zhao, Sun Yunxi, Li Guozhong, and Wu Ke

Subjects
Physics, Superconductivity, Paramagnetism, Field (physics), Condensed matter physics, Phase (matter), General Physics and Astronomy
Abstract

The structure, magnetic, and superconducting properties of the (Tl1-xAlx)2Ba2Ca2Cu3Oy with x = 0.05, 0.1, 0.15, 0.2 were studied. The TcR = 0 depends on whether the sample has a 2223 phase structure or has a 2212 phase structure. The magnetic properties in low field were measured and discussed.

Published
1989

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