PREPARATION AND CHARACTERIZATION OF TlBa2Ca2Cu3Oy WITH A DIFFERENT MAXIMUM Tc
We have succeeded to prepare Tl -1223 samples with a maximum Tc above 130K at ambient pressure using a conventional sealed quartz tube method. We found that, by adequately controlling the starting composition, it is possible to control the maximum Tc from ~120K to 130K. In order to seek the key factors for a drastic increase in the Tc, we carried out the measurements of the thermoelectric power, powder X-ray diffraction and neutron diffraction for these samples. As a result, it is found that the characteristics in the Tl -1223 samples with high Tc show essentially similar to those in the Hg -1223 with the highest Tc and are different from those in the Tl -1223 samples with low Tc. The details of the synthesis conditions, the transport properties and the refinements of the crystal structure will be presented.