Both of the off-diagonal Seebeck effect and the off-diagonal Peltier effect were investigated with the use of the same textured sample YBa2 Cu3 07-δ (Y-123) and the same experimental setup. The reliability of the measurement is studied by applying different heat-conductive mediums. The flatness of both of the sample and the heat-conducting block, and the matching between them are found very important for the reduction of the heat resistance. The annealing effect on the S is also studied and found in accordance with that studied by the thermoelectric power.

Received 10 November 2000; received in revised form 24 January 2001; accepted 27 February 2001 By using top seeding melt-textured growth (TSMTG) process, large single domain YBaz Cu3 07 JY2 Ba Cu O5 (YBCO) samples were prepared with addition of nanometric SnO2 and normal CeOy. Polarized light microscope studies at each step of the TSMTG process showed that before YBa2 Cu3 07 δ (123) melting, the Sn-based reacted products were uniformly distributed in micrometer scale; after solidification, the trapped YyBaCuO5 (211) and Sn-based inclusions were more homogeneously distributed and with mean sizes of about one micrometer. Composition images of scanning electronic microscope for the textured samples showed that, on the whole, the Sn-based inclusions were smaller than the 211. They must be on average below one micrometer in size. Although evidence was found that very fine Sn-based inclusions were uniformly trapped in 123 matrix, the fraction of them was small in comparison to that of 211. No significant enhancement of superconducting critical current density (Jc) was evidenced for the nanometric SnOy-doped samples at a low magnetic field (B<1 T). However, values of Jc were decreased at intermediate magnetic field (1<B<3 T). 2001 Elsevier Science B.V. All rights reserved.

idth at half-height of powder X-ray diffraction, the MgO powder was about 20nm in size on average. A supersonic vibration was introduced to destroy the accumulation of the ultrafme powder and to mix the powder with the YBa2 Cu3 07-δ precursor. The melt-process was employed to grow textured samples. From the Scanning Electron Microscope (SEM) graphs, some particles were found in the textured samples, which were about several nanometer in size. The composition of these particles, however, leaves to be identified. The magnetic critical current density (Jcm) at 77K dropped rapidly with the increase of Mg content.

The recent observation of superconductivity above 160 K under high pressures has prompted us to investigate the possibility of retaining such high-temperature superconductivity at ambient pressure by substituting Sr for Ba in Hg Ba2 Caz Cu3 08 (Hg-1223). High-purity (≥ 90%) Hg-1223 phase samples were synthesized with a nominal composition of Hgz Srx Ba2_x Caz Cu3 O8+& (where z=0.75 and x=0.0.5 or 1). By adding a second element, Pb or Mo, supposedly to the Hg site, (Hg, Pb/Mo)Sr2 Caz Cu3 O8+& with purity up to 90% was achieved. Unfortunately, Tc decreases with Sr substitution. The roles of Sr in the phase stability, and the synthesis conditions of the Sr based Hg-1223, and the Sr substitution effect on the Tc of these samples will be discussed.

Sol-gel is one of the effective techniques for preparing YBa2Cu3O7−δ (YBCO) coatings at relatively low cost. Its process from gel to oxide coatings, however, was not yet fully understood. This is one of the obstacles for achieving YBCO coatings with good superconducting properties. In this paper, we chose EDTA as the complexant to prepare gels with different kinds of M(EDTA)n−complexes, where M is any combination of Y, Ba, and Cu cations, in order to investigate the decomposition process of the gels with the help of Fourier transform infrared (FTIR) spectra. Comparing the FTIR spectra of the gel powders with those of the calcined powders, we found that the decomposed temperatures were different for different M(EDTA)n−complexes.We considered this was the cause of the Ba segregation (as BaCO3) in the coatings at low heating temperature, which in turn blocked the formation of high quality YBa2Cu3O7−δ.