Synthesis and study of the ceramic high-Tc superconductor Hg1-x TlxBa2Ca1.8Y0.2Cu3O8+δ (x=0.3, 0.5, 0.7, 0.9 and 1)

High-Tc superconducting ceramic samples of the form Hg1-x TlxBa2Ca1.8Y0.2Cu3O8+δ (x=0.3, 0.5, 0.7, 0.9 and 1) are prepared in a closed quartz tube at 8600C. The electrical resistance versus temperature is measured in the temperature range between 15 K and room temperature. The effect of magnetic field and applied electric current on the second stage of the transition is studied. It is found that the transition does not occur at a definite temperature but in a temperature range ΔT which may approach 50 K or even more. This is believed to be due to the very short coherence length (ζ=10A) of HTSCs or to the random motion of the magnetic flux. The results obtained in our work can give some information about superconducting grains and weak superconducting boundaries. (author)