<報文>滴下熱分解法による酸化物高温超伝導材料の合成と熱力学的性質

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Investigations were made on the low temperature synthesis and themodynamic properties of high temperatureoxide superconductors, La₂₋xSrxCuO₄c and YBa₂Cu₃O₇₋d. The oxides were prepared by the drip pyrolysis method from nitrate solution mixtures. It was found that La₂₋xSr₋xCuO₄₋d was formed at temperatures above 650 ℃in air, and YBa₂ Cu₃O₇₋d were formed at above 700℃ in air and in nitrogen atmosphere. Using TG-DSC, studies were made on the reaction mechanism of formation of YBa₂Cu₃O₇₋d from nitrate solution mixtures. It was shown that co-pyrolysis of yttrium and copper nitrates takes place below 400℃ to form Cu₂Y₂O₅ and CuO, and then the co-pyrolysis with barium nitrate occurs at temperatures around 700℃, well below 100℃ of the pyrolysis of simple barium nitrate. The oxygen nonstoichiometry and decomposition oxygen partial pressure of La₂₋xSr₋x CuO₄₋d were studied by means of the high temperature coulometric titration technique and thermogravimetry. The decomposition oxygen partial pressure of La₁.₉Sr₀.₁CuO₄₋d was found to be 10ˉ⁷˙¹ atm at 800℃. In 1 atm oxygen gas, La₂₋xSr₋xCuO₄₋d shows essentially stoichiometric composition. The nonstoichiometry, d, of La₂₋xSr₋xCuO₄₋d increased with decreasing oxygen partial pressure and exceeded x/2 (at which the Cu mean valance was 2+) without remarkable changes in the log d vs. log P(O₂) relationship, suggesting that the electronic structure of La₂₋xSr₋xCuO₄₋d is metallic.
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<報文>滴下熱分解法による酸化物高温超伝導材料の合成と熱力学的性質

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