Sub-solidus relations in CaO---BaO---CuO with and without carboxyl contamination
Resource
Physica C: Superconductivity 262 (1-2): 33-44
Journal
Physica C: Superconductivity
Journal Issue
262
Pages
33-44
Date Issued
1996
Date
1996
Author(s)
Lin, Sern-Hau
Abstract
The sub-solidus relations in the pseudo-ternary CaO-BaO-CuO system have been investigated at temperatures between 900 and 1000°C in both oxygen and (natural) air, and a tremendous effect has been found to result from the minute amount (∼ 450 ppm) of CO2 present in the latter atmosphere. In flowing oxygen, CaBa4Cu3O8 + x, CaBa7Cu3O11 and Ba1 - yCayCuO2 (0 ≦ y ≦ 0.08) solid solutions have been identified. On the other hand, in stagnant natural air, which contains ∼ 450 ppm CO2, there have been found oxycarbonates including CaBa4Cu2O6 + δ(CO3), CaBa8Cu3O8(CO3)4, and Ca1 - xBa8Cu4O10 - 2x(CO3)3 + x (x = 0 ∼ 0.35) solid solutions, which account for several controversial ternary "oxides" reported in the literature. The ternary phase diagrams for both atmospheres at 900°C are shown, while those at higher temperatures, up to 1000°C, are elucidated from the thermal stability studies of the detected oxides and oxycarbonates. Structural models are proposed for CaBa8Cu3O8(CO3)4 and Ca1 - xBa8Cu4O10 - 2x(CO3)3 + x.
Type
journal article
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