Synthesis and electrical transport of Hg0.8Tl0.2Ba2Ca2Cu3O8+delta

H(go.8)Tlo.2Ba2Ca2Cu3O8+delta compound was synthesized by using the high-pr essure-high-temperature technique in a belt type high pressure furnace. The applied pressure is 18 kbar and the temperature is raised to about 800 sim ilar to 900 degreesC during the sample synthesis. We found that the cooling process in synthesizing the precursor has a. significant effect on the sam ple synthesis condition and sample quality. By using the furnace - cooled p recursor in oxygen atmosphere, we could get the nearly single phase of Hgo. 8Tlo.2Ba2Ca2Cu3O8+delta With the two step annealing process. The effect of T1 substitution for Hg on the superconducting properties was investigated b y measuring the resistivity and the thermoelectric power as a function of t emperature.