Thermodynamic properties of melts of the Cu—In—La system

Abstract

Partial for the components and integral enthalpies of mixing of the ternary melts of the Cu—In—La system were determined for the first time by the method of calorimetry on five radial sections with a constant ratio of two components:, and (up to xIn = 0,02, 0,14, and 0,42, respectively) and and (up to xCu = 0,15 and 0,2, respectively) at 1220—1450 K. It is shown that when indium 1 is added to the CuxLa1-x melt, the thermal effect of its dissolution increases, which is caused by the formation of strong bonds between In and La. In the other two sections (and), the enthalpies of mixing of ternary melts decrease during dissolution. Using the reliable mixing enthalpies of the melts of the dual systems Cu—In(La) and In—La, similar parameters for liquid alloys of the Cu—In—La system were calculated according to various “geometric” and “analytical” models. It was found that the values calculated by the Redlich—Kister—Mujianu model with the triple contribution –200 agree with the determined enthalpies of mixing of melts of the Cu—In—La system within the limits of experimental errors. It was established that the minimum enthalpy of mixing of melts of the Cu—In—La system falls on the alloy of the In—La subsystem (−43,4 ± 2,1) at xLa = 0,4 at T = 1450 K, i. e., the largest contribution to the enthalpy of mixing of melts of the Cu—In—La system is made by boundary subsystem In—La. The activity of the components in the melts of this system was calculated according to the same model. It is shown that they exhibit small negative deviations from ideal solutions at 1450 K. From these data, G, S of melts of the Cu—In—La system were estimated. It was established that Gmin = –26 kJ/mol, Smin = –12 J/mol∙K, which are attributed to the In0.6La0.4 alloy. Keywords: calorimetry, copper, lanthanum, indium, thermodynamic properties, modeling, mixing enthalpies, activity of components.