YBa_2Cu_3O_xの相安定性と分解挙動

概要

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The phase stability and the decomposition behavior for the high T_c superconductor, YBa_2Cu_3O_x(x=6.92) , at 20°-1200℃ in O_2, air, N_2 and H_2 were studied by means of the thermogravimetry (TG), the differential thermal gas analysis (DTGA), the differential thermal analysis (DTA) and the liquid N_2 quenching. In the air, O_2 and N_2, the phase transition and the decomposition of YBa_2Cu_3O_x. take place according to the following five steps. Orthorhombic- YBa_2Cu_3O_x→Tetragonal- YBa_2Cu_3O_x(Tetra)→Tetra, BaCuO_2→Tetra, Y_2BaCuO_5, BaCuO_2→Y_2BaCuO_5, BaCuO_2, CuO The temperature and the oxygen content of specimens, when the phase transition and/or the decomposition take place, decrease along with the lowering oxygen partial pressure. Under hydrogen atmosphere, the decomposition takes four steps commencing with TG measurement. At the final step (around 900 ℃) , YBa_2Cu_3O_x decomposes to Cu metal, BaO and Ba_3Y_4O_3 At the second step (450℃) , Y_2O_3, Ba (OH)_2・H_2O, and Cu were already found. At the third (600℃) and the forth (750℃) steps, a phase unknown was detected. The formation of Ba (OH)_2・H_20 can be regarded to occur due to the reaction of BaO and H_2O. The decomposition process under hydrogen atmosphere is found to be very complicated.
社団法人日本セラミックス協会の論文
1988-04-01