The CaO-SrO-CuO-O2 system: phase equilibria and thermodynamic properties at 1123 K

Jacob, K. T. ; Markondeya Raj, P. ; Waseda, Y. (1995) The CaO-SrO-CuO-O2 system: phase equilibria and thermodynamic properties at 1123 K Journal of Phase Equilibria, 16 (2). pp. 113-120. ISSN 1054-9714

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Phase relationships in the CaO-SrO-CuO system in pure oxygen at 1.01 × 105 Pa pressure were determined by equilibrating different compositions at 1123 K for ∼120 h and analyzing the phases present in the quenched samples using X-ray diffraction (XRD), optical and scanning electron microscopy, and energy dispersive analysis of X-rays (EDAX). Four solid solution series were observed in the system. The CawSr1-wO monoxide solid solution with rock-salt structure was found to exhibit an asymmetric miscibility gap. The mixing properties of the monoxide system were deduced using a subregular solution model. For the (CaxSr1-x)2CuO3 series, a complete solid solution range with orthorhombic space groupImmm was obtained. Calcium substituted for strontium up to 68 at.% in SrCuO2+δ and 51.5 at.% in Sr14Cu24O41-δ. The tie lines between the solid solutions were determined accurately. The activity-composition relations in (CaxSr1-x)2CuO3, CaySr1-y,CuO2+δ, and (CazSr1-z)14Cu24O41-δsolid solutions were determined from experimental tie lines. Activities in the (CaxSr1-x)2CuO3 and CaySr1-yCuO2+δ series were close to the predictions of the Temkin model. The behavior of the (CazSr1-z)14Cu24O41-δ solid solution was more complex, with the activity of SrCu(24/14)O(41-δ)/14 exhibiting both positive and negative deviations from ideality. Gibbs energy of formation of the CaCuO2+δ metastable phase at 1123 K was deduced from an analysis of the phase diagram.

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ID Code:94949
Deposited On:10 Oct 2012 07:28
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