Experimental Phase‐Diagram Study and Thermodynamic Optimization of the Silver‐Strontium‐Copper‐Oxygen (Ag‐Sr‐Cu‐O) and Silver‐Calcium‐Copper‐Oxygen (Ag‐Ca‐Cu‐O) Systems

Abstract

The phase relations in the silver‐strontium‐copper‐oxygen (Ag‐Sr‐Cu‐O) and silver‐calcium‐copper‐oxygen (Ag‐Ca‐Cu‐O) systems were studied in oxygen, air, and nitrogen environments, using differential thermal analysis and energy‐dispersive X‐ray spectrometry. The presence of silver reduces the melting temperature of the oxide liquid to a monotectic in the strontium‐ and calcium‐containing systems by 62 and 82 K, respectively (to 1222 and 1244 K, respectively) in oxygen. The oxide liquid dissolves silver (up to a metallic ratio of 0.17) in the Ag‐Sr‐Cu‐O system in oxygen at a temperature slightly higher than that required for monotectic reaction. In the Ag‐Ca‐Cu‐O system, the silver content has been measured to be 0.29 (metallic ratio). The oxide systems have been optimized using the experimental data from monotectics and those from lower‐order systems that have been published previously. This work is part of a project to evaluate the phase relations within the silver‐bismuth‐strontium‐calcium‐copper‐oxygen (Ag‐Bi‐Sr‐Ca‐Cu‐O) system and, in particular, to focus on the influence of silver on the phase equilibria around the superconducting phases during partial‐melt processing.

Thermodynamic modeling of the Ca–Ag binary system

“…Well-developed thermodynamic database of Ag Bi Sr Ca Cu O system is very helpful to explain and predict these interface reactions [3]. For this purpose, some of the binary, ternary, quaternary subsystems in this five-components system have been assessed recently [2,4,5]. However, the thermodynamic parameters of Ca-Ag system have not been optimized.…”

Thermodynamic Optimization of the Silver—Bismuth—Strontium—Calcium—Copper—Oxygen (Ag‐Bi‐Sr‐Ca‐Cu‐O) System

“…16 The descriptions of the oxide compounds and the face-centered cubic (fcc) structure (silver) have been taken from previous assessments. [7][8][9][10][11] The liquid phase is described by the two-sublattice model for ionic liquids, 17,18 which allows a continuous description from the metal liquid to the oxide liquid, as well as the miscibility gap between them. The cationic sublattice contains all the metallic species that are present, with their usual valences, and the anionic sublattice contains the oxygen anions, as well as negatively charged vacancies, which also allows description of the metallic liquid.…”

Thermodynamic modeling of the Ag–Sr system

“…Some of the binary, ternary and quaternary subsystems of Ag-Bi-Sr-Ca-Cu-O have been well assessed recently [1,3]. There are some literature data for the Ag-Sr system [4,5].…”