摘要:

We compare the superlattice modulation, microstructure, and epitaxy of Tl2Ba2Ca2Cu3O10thin films grown on MgO [100] and SrTiO3 [100] substrates by dc diode sputtering. Films grown on MgO were found to be quite clean with thecaxis perpendicular to the substrate. However, no in‐plane orientational relationship to the substrate was found. Films grown on SrTiO3, on the other hand, showed very good epitaxy to the substrate despite the presence of second phases. Films grown on MgO also exhibited a longer coherence length of the superlattice modulation than those grown on SrTiO3under identical conditions.

ISSN:0003-6951    

DOI:10.1063/1.101387

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The critical current density (Jc) at 77 K and in 0 T of more than 3000 A/cm2has been obtained in the silver sheathed Bi‐Pb‐Sr‐Ca‐Cu‐O tape fabricated by the combination process of sintering and intermediate cold working. The decrease of theJcwith increasing magnetic field is much smaller in the tape prepared by this process than that prepared by sintering only. The improvement of theJcis attributed to the improvement of the coupling between the grains of the highTcphase. The process enhances the formation of the highTcphase and produces a highly oriented grain structure. These are considered to be responsible for the large improvement of the coupling.

ISSN:0003-6951    

DOI:10.1063/1.101319

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A synthesis procedure for producing high‐density Ba1−xKxBiO3has been developed. A novel melt‐processing technique is described which yields strong, near 100% dense superconducting material. This material is much more amenable to experimental study than the powder samples produced by the previous synthesis methods.

ISSN:0003-6951    

DOI:10.1063/1.101388

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Two kinds of sintering atmosphere, N2and air, were used to study the effect of atmosphere on the formation of the lowTcphase and the highTcphase. The annealing temperatures were 810 °C in N2and 850 °C in air. The resistivity measurements and the x‐ray diffraction analysis showed that while the fraction of the highTcphase continued to increase with sintering times in air, it did not increase in any appreciable amount even after 264 h of sintering in N2atmosphere. Compared with air, N2atmosphere enhanced the formation of the lowTcphase and inhibited the formation of the highTcphase.

ISSN:0003-6951    

DOI:10.1063/1.101320

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The Y and rare‐earth substitution for Ca in Bi2.1CaSr2Cu2O8+&dgr;is described with particular emphasis on Y substitution. We have prepared single phase, fully substituted material which exhibits an 8.0×b‐axis incommensurate structure, rather larger than the 4.75× structure in the parent superconductor. The infrared absorption spectra of the insulating fully substituted material are shown to have features very similar to that for YBa2Cu3O7−&dgr;. A solubility range is observed only at substitutions up to 5% at which point zero‐resistanceTcis raised from 90 to 101 K. This is shown to arise from 2 copper‐layer material and not from 3 copper‐layer material. Combined Y and Pb substitution yieldsn=2 material for whichTcremains fixed at 90 K, insensitive to annealing temperature and oxygen loading.

ISSN:0003-6951    

DOI:10.1063/1.101389

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report fast optical response measurements in predominantlyc‐axis oriented crystalline Y1Ba2Cu3O7−xsuperconducting thin films at the wavelength of 1.06 &mgr;m. We identify two distinct components contributing to the optical response: a nonbolometric (as fast as 1 ns) and a bolometric component (several ns). The bolometric component is stronger at temperatures in the vicinity of the transition region to the normal state. The nonbolometric component is dominant at temperatures below the transition region showing weak temperature dependence and a linear dependence on the bias current. This nonbolometric component may be evidence for nonequilibrium effects (e.g., breaking of Cooper pairs and generation of quasiparticles or other mechanisms). These results suggest that with proper optimization of device parameters (its geometry, critical current density, etc.) high‐speed detectors with reasonable sensitivity covering a broad electromagnetic spectrum (visible and infrared) may be developed.

ISSN:0003-6951    

DOI:10.1063/1.101390

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A unique method of hot rolling is described which fabricates high performance plate‐shaped magnets from a cast Pr17Fe76.5B5Cu1.5alloy. A flat ingot of the alloy with fine‐scale columnar grains of a Pr2Fe14B phase is prepared by chill casting. The ingot is hot rolled in such a way that the roll pressure is applied perpendicular to the preferential growth direction of the columnar grains. A maximum energy product of 25.3 MG Oe has been obtained by this method.

ISSN:0003-6951    

DOI:10.1063/1.101391

出版商:AIP    

年代:1989

数据来源: AIP