High pressure synthesis of Hg1223 superconductor under highly oxidizing atmosphere

We tried to prepare the mercury-based superconductor, HgBa 2Ca 2Cu 3O 8+δ (Hg1223), under highly oxidizing atmosphere using a high pressure technique. Samples containing Hg1223 as the main phase with T C=90–122 K were obtained. CuO and a new phase were included in the samples as impurities. The a-axes of the samples were shorter than the values ever reported for Hg1223 with T C=135 K. These results suggest that our Hg1223 samples had excess hole concentrations, i.e. they are over-doped. The irreversibility field ( B irr) was measured for two samples with T C=118 and 94 K. They had almost the same normalized temperature (1− T/T C) dependence of B irr.