Thermodynamic properties of alloys of the binary In–Yb system

Abstract

The thermochemical properties of melts of the binary In-Yb system were studied by the calorimetry method at 1160-1380 K over the whole concentration interval. It was shown that significant negative heat effects of mixing are characteristic features for these melts. Using the ideal associated solution (IAS) model, the activities of components, Gibbs energies and the entropies of mixing in the alloys, and the phase diagram of this system were calculated. They agree with the data from literature.Alloys of the rare-earth metals with p-elements of the third group are promising as superconductors, catalysts and promoters, as well as cathode materials with various emission properties [1,2]. However, there are only few works in the literature devoted to investigation of thermodynamic properties of indium-lanthanide alloys. Even those which were conducted, are related mostly to the alloys containing 75% indium or more. This is caused by poor accessibility of the components in pure state, and by instability of their alloys in air.Nevertheless, in the rest, these alloys are quite easy objects to investigate, since they are mostly low-melting, non-volatile, and not interacting with refractory crucible materials. This allows us to conduct investigation of thermodynamic properties of the In-Ln melts using calorimetry method over wide concentration ranges. Our research group has already done it successfully for the Eu-In [3] and the Ce-In systems. The present work is devoted to the In-Yb liquid alloys. Studying wide range of such systems, including the Gd-In and the In-La, will give an opportunity to determine the regularities of interaction between the components of the In-Ln systems.The phase diagram of the In-Yb system was investigated by McMasters et al. [4] using differential thermal analysis, metallography and X-ray diffraction methods. Fields of solid solutions, containing up to 1 at % In, were found for two ytterbium modifications (β-and γ-Yb). Five intermetallics were identified: YbIn 3 , YbIn 2 , YbIn, Yb 2 In, and Yb 5 In 2 . Two of them melt congruently (YbIn 2 , YbIn), and two else decompose by peritectic reactions (YbIn 3 , Yb 2 In). For the last intermetallic, the authors [4] proposed stoichiometry Yb 5 In 2 and peritectic melting. However, later in the work [5] the crystal structure and composition of this compound were updated-Yb 8 In 3 . A review [6] gave the phase diagram of the In-Yb system which includes this modification. Shifting of the composition from 71.4 to 72.7 at % Yb makes peritectic melting type of the Yb 8 In 3 compound questionable-instead, congruent melting becomes possible. Unfortunately, in both the handbook [7] and the CALPHAD thermodynamic assessment [8] this updating of stoichiometry was missed, and an old variant was used-Yb 5 In 2 .

Thermodynamic properties of alloys of the Co-Sc and Co-Y systems

“…Accordingly to our model, Co 17 Y 2 also melts congruently; in alternative case it should be necessary to propose lower melting temperature for this compound, than given in [17,29]. We did not consider the decomposition of Co 5 Y into Co 17 Y 2 and Co 7 Y 2 at lowered tem- Liquidus slopes in the range between the melting point of pure scandium and the nearest to it eutectic or peritectic, for selected Sc-element systems, as dependences from the mixing enthalpies of melts of these systems at equiatomic composition: ΔH(x Sc = 0.5), kJ/mol: a-our data (IAS model) [38,44], b [49], c [48], d [42] + our [44], e [43], f [10], g [51], h [44,46], i [45]+ [46], k [50], l [52], m [47], n [41] + our [38]. Dashed bar contains the most reliable data among the systems with low solubility of the second component in the solid scandium.…”

“…To clarify this question, we need to survey a number of binary systems of scandium with metals, which show relatively similar degrees of interaction between the components to the Co-Sc system [10,38,[41][42][43][44][45][46][47][48][49][50][51][52][53].…”