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Start Over Author "Guo, Yanqun" Publisher iop publishing
10 results on '"Guo, Yanqun"'

4. Crucial role of oxygen-deficient LaMnO3−δ cap buffer layer in enhancement of current carrying capability of MOD-YBCO coated conductors.

Author

Fan, Feng, Lu, Yuming, Liu, Zhiyong, Zhou, Difan, Guo, Yanqun, Bai, Chuanyi, Li, Minjuan, and Cai, Chuanbing

Subjects
BUFFER layers, X-ray diffraction measurement, REACTIVE sputtering, EPITAXY, LATTICE constants, SURFACE morphology, COPPER films
Abstract

LaMnO3−δ (LMO) films with different oxygen contents are deposited on Epi-MgO/IBAD-MgO templates using reactive magnetron sputtering under varying temperatures and atmospheres. Subsequent YBa2Cu3O7−δ (YBCO) films are grown on LMO layers by metal-organic deposition (MOD) method. X-ray diffraction measurements reveal that YBCO texture cannot be further improved when the full width at half maximum (FWHM) values of LMO (011) φ-scans (evaluation on in-plane alignment) and LMO (002) ω-scans (evaluation on out-of-plane alignment) for LMO films are less than 8° and 4°, respectively. Sharp orientation with in-plane FWHM value of <3° for YBCO (103) φ-scan and out-of-plane FWHM value of <1.5° for YBCO (006) ω-scan can typically be achieved in YBCO films. Precise control of growth conditions, especially atmosphere, remains a feasible way to modify the surface of LMO films. It induces changes in oxygen content, lattice structure and surface morphology of LMO, and further affects the epitaxial growth of superconducting layers. Oxygen-deficient LMO with expanded lattice parameters and flat surface can effectively suppress the non-c-axis oriented YBCO, thereby enhancing the current carrying capability. The 500 m long YBCO coated conductors with conditioned LMO layers have an inductive critical current (Ic) ranging from 358 to 437 A/12 mm width with an average value of 398 A/12 mm width. [ABSTRACT FROM AUTHOR]

Published
2020
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8. Transient liquid assisted nucleation mechanism of YBa 2 Cu 3 O 7− δ in coated conductor films derived by BaF 2 process

Author

Cai Chuanbing, Shu Gang-Qiang, Bai Chuanyi, Liu Zhiyong, Lu Yuming, Lu Qi, Yang Wen-Tao, Guo Yanqun, and Gu Zhao-Hui

Subjects
Superconductivity, Supersaturation, Materials science, Nucleation, General Physics and Astronomy, chemistry.chemical_element, Copper, law.invention, chemistry, Chemical engineering, law, Physical vapor deposition, Deposition (phase transition), Crystallization, Type-II superconductor
Abstract

It is significant for low-cost preparation of YBa2Cu3O7−δ (YBCO) coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the present work, a distinct nucleation mechanism was proposed based on a transient liquid phase induced by the size effect as well as near-equilibrium assumption. With this scheme the nucleation of YBCO prepared by metal–organic deposition (MOD) or the physical vapor deposition BaF2 process was semi-quantitatively analyzed, revealing that the direct driving force for nucleation is YBCO supersaturation in the liquid phase. The theoretical analysis on the nucleation orientation portion is evidenced by the experimental result.

Published
2015

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