31. |
Microwave surface resistance of magnetron‐sputtered Tl‐Ba‐Ca‐Cu‐O films on silver substrates |
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Applied Physics Letters,
Volume 56,
Issue 21,
1990,
Page 2147-2149
D. W. Cooke,
E. R. Gray,
P. N. Arendt,
G. A. Reeves,
R. J. Houlton,
N. E. Elliott,
D. R. Brown,
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摘要:
Surface resistance measurements on Tl‐Ba‐Ca‐Cu‐O thick films (∼15 &mgr;m) magnetron sputtered onto BaF2‐buffered, silver‐based (Consil 995) substrates have been made at a microwave frequency of 22 GHz. The relatively large‐area films (∼5 cm2) are characterized by surface resistance values of 6.9±2 m&OHgr; at 11.3 K and 30.2±1 m&OHgr; at 77 K; the corresponding values for Cu are 10 and 22 m&OHgr;, respectively. These results demonstrate that Tl‐Ba‐Ca‐Cu‐O can be deposited ontolarge‐area,metallicsubstrates with characteristic surface resistance values lower than Cu at 4 K. Orientation of the film should improve the surface resistance at 77 K, thereby making the fabrication of microwave cavities that are superior to Cu possible.
ISSN:0003-6951
DOI:10.1063/1.102954
出版商:AIP
年代:1990
数据来源: AIP
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32. |
Structural and chemical stability in nonrandom silver‐YBa2Cu3O7composites in the presence of water |
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Applied Physics Letters,
Volume 56,
Issue 21,
1990,
Page 2150-2151
D. Veretnik,
S. Reich,
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摘要:
Accelerated water and moisture degradation of YBa2Cu3O7(YBCO)‐silver nonrandom composites is studied. Oxygen evolution for these composites immersed in water at 65 °C was compared with that for regular YBCO ceramic material prepared under similar sintering conditions. Time evolution of the decay of crystalline structure was followed by x‐ray diffraction for the composite material and for the regular YBCO ceramic. We find that the nonrandom Ag‐YBCO composite exhibits high chemical and structural stability in the presence of water; this advantageous property is probably due to the encapsulation of the YBCO grains with silver in this composite material.
ISSN:0003-6951
DOI:10.1063/1.103240
出版商:AIP
年代:1990
数据来源: AIP
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33. |
Origin of anomalous energy spreads in photoelectron beams |
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Applied Physics Letters,
Volume 56,
Issue 21,
1990,
Page 2152-2153
H.‐J. Drouhin,
Ph. Bre´chet,
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摘要:
The use of photocathodes as intense monoenergetic electron sources seems very promising. Yet, many experimenters have observed large energy spreads, increasing with the emitted current, which remained unexplained. Here, we analyze a mechanism which accounts well for these effects.
ISSN:0003-6951
DOI:10.1063/1.102955
出版商:AIP
年代:1990
数据来源: AIP
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