摘要:

We have prepared YBa2Cu3O7−&dgr;(YBCO) superconducting wires by electrophoretic deposition. Ag wire was used as a substrate. Adding a small amount of BaF2tends to remove cracks in the YBCO layer which develop during the heating process. The suppression of cracks produced a dramatic improvement in the critical current density (Jc). At 77 K,Jcincreased from 18 A/cm2 for BaF2‐free YBCO wire to 646 A/cm2 for a critical concentration of 2.7 wt% BaF2after which it decreased monotonically with increasing BaF2content. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115526

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We fabricated screen‐printed Ag‐(Bi,Pb)2Sr2Ca2Cu3Oxmonofilament and multifilament tapes with filament number 1≤N≤5. AsNincreases, the critical currentIcincreases monotonically until it reaches 54 A (77 K, 0 T) forN=5, while the critical current densityJcis around 1.6×104A/cm2(77 K, 0 T) nearly independent ofN. The bend strain tolerance is found to decrease with increasingN. For monofilament tapes the strain tolerance is 2%–3% strain while for multifilament tapes it decreases to ∼1% atN=3 and ∼0.4% atN=5. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115527

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The magnetoimpedance (MI) effect of amorphous Co70.4Fe4.6Si15B10ribbons, subjected to different annealing conditions with and without an external field, has been measured up to a frequency of 100 kHz. We show that the large MI effect is the result of transverse magnetic anisotropy, which is present in the as‐cast and the suitably field‐annealed samples. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115528

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present results of temperature and magnetic field dependent resistivity &rgr;(H,T) and bulk magnetizationM(H,T) measurements on post‐annealed La0.7Ca0.3MnO3thin films that were grown via pulsed‐laser deposition. Both the resistivity and the anomalously large negative magnetoresistance peak near the ferromagnetic ordering temperature (Tc=250 K), with &Dgr;&rgr;/&rgr;0=−85% at 50 kOe. A clear correlation is found between &rgr; andMthat is described by the phenomenological expression &rgr;(H,T)∝exp[−M(H,T)/M0]. This correlation reflects the important interplay between transport and magnetism in this system, and suggests that the transport belowTcinvolves polaron hopping. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115529

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In silicon wafer bonding, the initial contact area spreads laterally with a typical speed on the order of 10 mm/s. We observed that this lateral bonding speed increases with decreasing ambient pressure, and is independent of the distance of the contact front to the rim of the wafers and independent of wafer thickness. From these results, we conclude that the lateral bonding speed is mainly determined by pressing the ambient gas out between the two wafers from a very localized area close to the propagating bonding front. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115530

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Voltage offsets in the polarization‐voltage characteristics of Pb(Zr,Ti)O3capacitors can be induced by either thermal or optical processes. The thermally (optically) induced voltage shift occurs by heating (illuminating) the sample under remanence or a saturating bias. Generally speaking, the thermally induced voltage shifts are greater than those obtained optically; this is attributed to the role of oxygen vacancy‐related defect dipoles throughout the film. We find that the inclusion of a dopant element that occupies a portion of the Ti(Zr) sites and has an oxidation state greater than +4 reduces the thermally induced voltage shifts observed in the capacitors. This may result because these particular dopants reduce the oxygen vacancy density and, hence, the defect‐dipole contribution to the voltage shift. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115531

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new simple transport model is used to describe the dependence of the electrical characteristics of the epitaxial layer on the growth parameters in low‐pressure metalorganic chemical vapor deposition. The important parameters of this model are the mean velocity of the gases and the [V]/[III] ratio. Undoped GaAs epitaxial layers are prepared at various operating pressures. A semi‐empirical correlation relating the reactor pressure and flow rate is established that dictates the operating conditions for a single set of film properties. This enables growth of a material with constant characteristics while pressure can be varied. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115532

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Micromachining Teflon was achieved by direct exposure to synchrotron radiation and the microstructures made had the smallest surface detail down to 20 &mgr;m with structural height of more than 200 &mgr;m, that is, aspect ratio on the order of 10. The quality of micromachining Teflon by this process was found to be critically dependent on photon flux of the synchrotron radiation. Analysis of the mass distribution of gaseous species formed upon this process suggested that photochemical processes rather than pyrolytic processes may still dominate. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115533

出版商:AIP    

年代:1995

数据来源: AIP