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COMBINED ANALYSIS OF DEFECT CONFIGURATION OF DEFORMED BRASS BY POSITRON ANNIHILATION AND X-RAY DIFFRACTION
TENG Feng en, LIU Baozhang, LI Yanqin
Chin. Phys. Lett. 1990, 7 (7):
312-315
.
The microstructure of alpha brass deformed to various degree ε was examined with positron annihilation technique and X-ray profile analysis. Stretch stress δ, positron annihilation probabilities Γ1, effective subgrain size Deff, positron lifetime T1 , dislocation density ρ, positron lifetime T2 and T etc. were measured as functions of deformation degree ε . Combined analyses of these curves were performed and positron annihilation models of single vacancy, dislocation, vacancy group and microvoid were suggested.
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STUDY OF THE PROPERTIES OF INFRARED INTERSUBBAND
TRANSITION IN DOPED GaAs/A1xGa1-xAs MULTIPLE QUANTUM WELLS
CHEN Zhenghao, CUI Dafu, ZHOU Junming, PAN Shaohua, HUANG Qi,
ZHOU Yueliang, LÜ, Huibin, XIE Yuanlin, FENG Simin, YANG Guozhen*
Chin. Phys. Lett. 1990, 7 (7):
319-322
.
The properties of intersubband transition of GaAs/A1xGa1-xAs multiple quantum wells with various well widths and doped-well concentrations have been studied. Both theoretical and experimental results are in good agreement. For the appropriate well width and higher doping concentration, we directly observed two intersubband absorption peaks from E1 →E2 and E2→ E3 transitions in well. The experimental results and theoretical analysis are given.
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HIGH-Tc SUPERCONDUCTING PROPERTIES OF YBa2Cu3-xSnx O7-y SYSTEM
WANG Yuxia, RUAN Yaozhong, TAN Yudong, WANG Xiaozhong, ZHOU Guien*, FAN Chenggao*, ZHANG Yuheng*
Chin. Phys. Lett. 1990, 7 (7):
326-329
.
The effect of Sn concentration on the superconducting properties and structure of YBa2Cu3-xSnx O7-y system were systematically investigated. The zero resistance temperature was found to be above 90K as z ranges from 0 to 1.1. For x > 1.3, the system exhibited no superconducting properties at liquid nitrogen temperature. The results of X-ray diffraction showed a regular pattern of mixed structures of 123 phase and a new phase in the system with the increase of Sn concentration. TEM analysis suggested that the new phase might be BaSnO3 with deformed perovskite structure and about 6% of Cu were substituted by Sn in the 123 phase at x = 1.0. It is therefore likely that the new phase modulates the structure of 123 phase and stabilize the 123 phase. Although the Sn atoms enter 123 phase and occupy the Cu sites in the Cu-O chain and break the chain, the system remains with Tc > 90K. Consequently, the Cu-O chain plays a less important role in the high-Tc superconductivity.
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13 articles
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