摘要
The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)(2), BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-delta, BaCuO2, Y2BaCuO5 and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. The relevant activation energies were calculated from thermogravimetric data. It is found that the reaction pathway significantly depends on the thermal stability of the Ba precursors. Binary BaO-CuO phases form at low temperature (650 similar to 700 degreesC) when in presence of easy- to -decompose Ba precursors, and then slowly transform to ternary compounds. On the contrary, when Ba ions are released at temperature higher than 900 degreesC, ternary phases form directly from the components.
The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)(2), BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-delta, BaCuO2, Y2BaCuO5 and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. The relevant activation energies were calculated from thermogravimetric data. It is found that the reaction pathway significantly depends on the thermal stability of the Ba precursors. Binary BaO-CuO phases form at low temperature (650 similar to 700 degreesC) when in presence of easy- to -decompose Ba precursors, and then slowly transform to ternary compounds. On the contrary, when Ba ions are released at temperature higher than 900 degreesC, ternary phases form directly from the components.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofItaly