A phase relation study of Bi-based copper oxide super conductors as a funcion of partial oxgyen pressure

摘要

Influence of partial oxygen pressure on the stabilities of Bi_4Sr_8Cu_5O_x (bi-4085) and Bi_2Sr_2Ca_2Cu_3O_x (bi-2223) have been investigted for th first time, using a newly developed apparatus in which high-temeprature X-ray diffraction measurements and microscope observtiosn are simultaneously perfromed under a quantitative cotnrol of atmosphere in the temeprature range between 780 and 1100 deg C under the partial melting at 880 deg C and changes mainly toSrCu_2O_2 with a liquid pahse, which would be formed by a reduciotn from Cu~2+ to Cu~1+ during heating. On the other hand, the kmelting poitn o the specimens having the nominal composition of Bi-2223 decreases with decreasign the partial oxygen pressure. In a N_2 gas flow, he melting poitn of 830 deg C whcih is about 100 deg C lower han tha in air, is observe ogether with changes t (Sr,Ca)CuO_2 and a liquid pahse. No cuprous phase is detected in this system.