High critical current densities found for thick Nb12Al3Ge superconducting deposits made by high‐rate sputtering
作者:
S. D. Dahlgren,
D. M. Kroeger,
期刊:
Journal of Applied Physics
(AIP Available online 1973)
卷期:
Volume 44,
issue 12
页码: 5595-5598
ISSN:0021-8979
年代: 1973
DOI:10.1063/1.1662202
出版商: AIP
数据来源: AIP
摘要:
Superconducting critical current densities up to 5.2 × 105A/cm2at 75 kOe and 4.2°K, and up to 4.4 × 105A/cm2at 100 kOe were measured for a 66‐&mgr;m‐thick Nb12Al3Ge deposit made at a rate of 1 &mgr;m/min by high‐rate sputtering. Current‐density‐vs‐transverse‐magnetic‐field curves were either linear or nearly linear, and the current density dropped only 33% over the field range investigated (50–100 kOe). The sample that carried the highest current densities was deposited at 20°C and heat treated one day at 750°C. Current densities for another sample from the same deposit, but heat treated 20 days at 750°C, were about 14% lower than for the sample heat treated one day. The deposits were body‐centered‐cubic (bcc) when deposited at 20°C. Heat treatment at 750°C produced a single metastableA‐15 phase containing grains of 350‐Å diameter; the small grain size presumably accounted for the high current density. Current densities measured with the field perpendicular to the deposit plane were only about 14% lower than with the field parallel to the deposit plane, which indicated theA‐15 phase grains formed by heat treatment at 750°C were nearly equiaxed. The high current density results and the availability of high‐rate sputtering equipment encourage fabrication of practical quantities of sputter‐deposited Nb&sngbnd;Al&sngbnd;Ge superconducting products. Estimated fabrication rates and costs were reasonable.
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