Polycrystalline samples of Lu0.5Ca0.5Ba1.4Sr0.6Cu3O6 without oxygen in the blocking layer of the so-called Cu(1)O chain have been prepared by the conventional solid-state reaction method. The onset temperature of the superconducting transition Tc onset = 80 K observed in the magnetic susceptibility measurement for the sample with the oxygen content of 5.87 is the highest record in the REBa2Cu3O6 (RE: rare-earth element) phase. The hole concentration in the superconductive Cu(2)O2 plane estimated from the thermoelectric power at R. T. is about 0.12 (/Cu(2)), indicating that the sample is still situated in the underdoped region. We have also investigated the effect of the introduction of oxygen into the blocking layer on Tc. It has been found that Tc takes a minimum at 6 + δ ~ 6.1 and the maximum at 6 + δ ~ 6.5 in Lu0.5Ca0.5Ba1.4Sr0.6Cu3O6+ δ.
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