Journal of Alloys and Compounds 394 (2005) 63–68 Electronic properties and viscosity of liquid Pb–Sn alloys Yu. Plevachuk a, ∗ , V. Sklyarchuk a , A. Yakymovych a , B. Willers b , S. Eckert b a Ivan Franko National University, Faculty of Physics, 8 Kyrylo and Mefodij Street, 79005 Lviv, Ukraine b Forschungszentrum Rossendorf, P.O. Box 510119, 01314 Dresden, Germany Received 13 October 2004; accepted 27 October 2004 Available online 19 December 2004 Abstract Electrical conductivity, thermopower and viscosity of liquid Pb–Sn alloys are investigated in a wide temperature range. The revealed discrepancies between heating and cooling curves of temperature dependencies of some electrophysical and structural-sensitive properties, as well as a hysteresis observed in the course of heating–cooling cycles suggest a metastable microheterogeneous structure of the Pb–Sn melts. © 2004 Elsevier B.V. All rights reserved. PACS: 61.10.Eq; 61.25.Mv; 66.20 Keywords: Metals; Chemical synthesis; Electronic transport; Electron–electron interactions 1. Introduction A number of studies dedicated to eutectic and near- eutectic alloys revealed that the behavior and properties of these systems are ambiguous and contradictory [1,2]. Dif- ferent models based on a statistical distribution of atoms in the melt or on a quasi-eutectical model, which was not identified with a crystalline eutectic but regarded in a dy- namic sense, have been developed (see [1] and references therein). It should be noted that from a structural stand- point the concept of “quasi-eutectic” is not at variance with current ideas about the fluctuation origin of the concentra- tion irregularity. Eutectic melts can be described as consist- ing of microregions with fuzzy edges whose atomic con- centration is close to those of the solid solutions compos- ing the eutectic. Concentration heterogeneities represent the melt areas of hundreds or even thousands of Angstroems en- riched by mainly one component. Nevertheless, this special structure of the liquid state is reflected on the temperature– concentration phase diagrams. Continuous mass exchange between these microregions takes place. Because of differ- ent approaches for the interpretation of diffractometer data, direct structural studies do not reflect completely the micro- ∗ Corresponding author. Tel.: +380 322 964594; fax: +380 322 631565. E-mail address: plevachuk@mail.lviv.ua (Yu. Plevachuk). heterogeneous structure of eutectic melts. Results for a quan- titative assessment of structure investigations suggest either a quasi-eutectic (statistical) or an intermediate atom distribu- tion. More reliable information about the structural heterogene- ity of the melt can be obtained from studies of the electro- physical and structure-sensitive properties. Among different eutectics lead-tin alloys have considerable potential for ad- vanced structural and electronic applications. The intensive interest in these solder alloys is attributed to their low cost and unique material properties including the high superplas- tic properties, low melting temperature, wettability, and good electrical conductivity [2]. However, different limitations to practical applications like the strain hardening or the exces- sive growth of intermetallic phases at the solder-substrate joint interfaces remain, and the understanding of the mi- crostructure of these alloys is still the subject of recent works [3–5]. The density investigations of the Pb–Sn eutectic by a gamma-ray absorption method revealed anomalies on the density polytherms, which were explained as transition of the quasi-eutectic melt to the micro-homogeneous state [6,7]. According to the new density and diffraction measurements irreversible structural changes occur in the eutectic Pb–Sn melt as a function of temperature [8]. Taking into account re- cent results reported for other eutectics [9], suggesting differ- ent temperature dependencies of physical properties during 0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.10.051