The Cu-Li-Sn Phase Diagram: Isopleths, Liquidus Projection and Reaction Scheme.

The Cu-Li-Sn phase diagram was constructed based on XRD and DTA data of 60 different alloy compositions. Eight ternary phases and 14 binary solid phases form 44 invariant ternary reactions, which are illustrated by a Scheil-Schulz reaction scheme and a liquidus projection. Phase equilibria as a function of concentration and temperature are shown along nine isopleths. This report together with an earlier publication of our group provides for the first time comprehensive investigations of phase equilibria and respective phase diagrams. Most of the phase equilibria could be established based on our experimental results. Only in the Li-rich part where many binary and ternary compounds are present estimations had to be done which are all indicated by dashed lines. A stable ternary miscibility gap could be found which was predicted by modelling the liquid ternary phase in a recent work. The phase diagrams are a crucial input for material databases and thermodynamic optimizations regarding new anode materials for high-power Li-ion batteries.

Enthalpy Effect of Adding Cobalt to Liquid Sn-3.8Ag-0.7Cu Lead-Free Solder Alloy: Difference between Bulk and Nanosized Cobalt.

Heat effects for the addition of Co in bulk and nanosized forms into the liquid Sn-3.8Ag-0.7Cu alloy were studied using drop calorimetry at four temperatures between 673 and 1173 K. Significant differences in the heat effects between nano and bulk Co additions were observed. The considerably more exothermic values of the measured enthalpy for nano Co additions are connected with the loss of the surface enthalpy of the nanoparticles due to the elimination of the surface of the nanoparticles upon their dissolution in the liquid alloy. This effect is shown to be independent of the calorimeter temperature (it depends only on the dropping temperature through the temperature dependence of the surface energy of the nanoparticles). Integral and partial enthalpies of mixing for Co in the liquid SAC-alloy were evaluated from the experimental data.

CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries.

The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu-Sn alloys as anode materials for Li-ion batteries.

New refinement of Ni5.20Sn8.7Zn4.16Cu1.04 and its non-isotypy with Ni2Sn2Zn.

The noncentrosymmetric space group P43m but a pseudocentric cubic crystal structure were reported for the compound Ni5.20Sn8.7Zn4.16Cu1.04 [Larsson et al. (1994). Acta Cryst. C50, 9-12]. The recently described Ni2Sn2Zn shows a closely related structure, although it is centrosymmetric and contains additional voids which are partially occupied. Therefore, a new refinement of Ni5.20Sn8.7Zn4.16Cu1.04 based on the originally published structure factors was performed. The results indicate that the structure can indeed be described in the centrosymmetric space group Pm3m; no justification for the absence of the inversion centre could be found within the accuracy of the available data. In comparison with Ni2Sn2Zn, slight but significant differences were confirmed; consequently, the two structures are topologically related but not isotypic.

Enthalpies of mixing of liquid ternary Co-Li-Sn alloys.

ABSTRACT: The partial and integral molar enthalpies of mixing of liquid Co-Li-Sn alloys were determined using drop calorimetry. The investigations were performed along six sections by the addition of lithium to mixtures with the compositions [Formula: see text]/[Formula: see text] ≈ 2:98, [Formula: see text]/[Formula: see text] ≈ 1:9, and [Formula: see text]/[Formula: see text] ≈ 3:17 as well as by the addition of cobalt to mixtures with the compositions [Formula: see text]/[Formula: see text] ≈ 3:17, [Formula: see text]/[Formula: see text] ≈ 1:2, and [Formula: see text]/[Formula: see text] ≈ 1:1 at a temperature of 1,173 K. The Co-Li-Sn system shows exothermic behavior of the integral molar enthalpy of mixing in the investigated concentration range. The integral molar enthalpy of mixing of liquid Co-Li system was calculated by Miedema's model to fit our measured ternary data using an extended Redlich-Kister-Muggianu model for substitutional solutions.

Ni2Sn2Zn from single-crystal X-ray diffraction.

Dinickel ditin zinc, Ni(2)Sn(2)Zn, crystallizes in the cubic space group Pm3m, with a lattice parameter of a = 8.845 (1) Å and with all atoms occupying special positions. The crystal structure exhibits pronounced similarities with that of the quaternary compound Ni(5.20)Sn(8.7)Zn(4.16)Cu(1.04). It shares structural features with other compounds in the Ni-Sn-Zn system, such as Ni(5)Sn(4)Zn and Ni(3)Sn(2).

Ni(5-δ)Sn4Zn (δ~0.25) from single-crystal data.

Work on the ternary Ni-Sn-Zn phase diagram revealed the existence of the title compound pentanickel tetratin zinc, Ni(3.17)Sn(2.67)Zn(0.67) [Schmetterer et al. (2012). Intermetallics, doi:10.1016/j.intermet.2011.05.025]. It crystallizes in the Ni(5)Ga(3)Ge(2) structure type (orthorhombic, Cmcm) and is related to the InNi(2) type (hexagonal, P6(3)/mmc) of the neighbouring Ni(3)Sn(2) high-temperature (HT) phase, but is not a superstructure. The crystal structure was determined using single-crystal X-ray diffraction. Its homogeneity range was characterized using electron microprobe analysis. Phase analysis at various temperatures indicated that the phase decomposes between 1073 and 1173 K, where a more extended ternary solid solution of the Ni(3)Sn(2) HT phase was found instead.

A new experimental phase diagram investigation of Cu-Sb.

ABSTRACT: The binary system Cu-Sb is a constituent system that is studied in investigations of technically important ternary and quaternary alloy systems (e.g., casting alloys and lead-free solders). Although this binary system has been thoroughly investigated over the last century, there are still some uncertainties regarding its high-temperature phases. Thus, parts of its phase diagram have been drawn with dashed lines in reviews published in the literature. The aim of this work was to resolve these uncertainties in the current phase diagram of Cu-Sb by performing XRD, SEM-EDX, EPMA, and DTA. The results from thermal analysis agreed well with those given in the literature, although some modifications due to the invariant reaction temperatures were necessary. In particular, reactions located on the Cu-rich side of the nonquenchable high-temperature ß phase (BiF3-type) left considerable scope for interpretation. Generally, the structural descriptions of the various binary phases given in the literature were verified. The range of homogeneity of the ε phase (Cu3Ti type) was found to be higher on the Sb-rich side. Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work). Further phase transformations that had previously only been estimated were confirmed, and their characteristic temperatures were determined.

Enthalpies of mixing of liquid systems for lead free soldering: Al-Cu-Sn system.

The present work refers to high-temperature drop calorimetric measurements on liquid Al-Cu, Al-Sn, and Al-Cu-Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al-Cu, and over the entire concentrational range in case of Al-Sn. Measurements in the ternary Al-Cu-Sn system were performed along the following cross-sections: x(Al)/x(Cu) = 1:1, x(Al)/x(Sn) = 1:1, x(Cu)/x(Sn) = 7:3, x(Cu)/x(Sn) = 1:1, and x(Cu)/x(Sn) = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich-Kister-Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. -18,000 J/mol in the Al-Cu binary and a maximum of approx. 4000 J/mol in the Al-Sn binary system. The Al-Cu-Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.

The high-temperature phase equilibria of the Ni-Sn-Zn system: Isothermal sections.

In this work three complete isothermal sections of the Ni-Sn-Zn system at 700, 800 and 900 °C are presented. They were constructed based on experimental investigation of more than 60 alloy samples. Powder XRD, single crystal XRD, EPMA, and DTA measurements on selected samples were carried out. Two new ternary compounds, designated as τ2 (Ni5Sn4Zn) and τ3 (Ni7Sn9Zn5), were identified and their homogeneity ranges and crystal structures could be described. Whereas τ3 is only present at 700 °C, the τ2-phase was found at both 700 and 800 °C. No truly ternary compound could be found in the isothermal section at 900 °C. A seemingly ternary compound at 20 at% Sn in the Ni-rich part of Ni-Sn-Zn was found at 800 and 900 °C. Our XRD results, however, indicate that this phase is a ternary solid solution of Ni3Sn-HT from constituent binary Ni-Sn. It is stabilized to lower temperatures by additions of Zn. These new experimental results will provide valuable information to the thermodynamic description of alloy systems relevant for high-temperature lead-free soldering.