- Email: [email protected]
Structural and physical studies of the Ag-rich alloys from Ag-Li system
Thermochimica Acta 673 (2019) 185–191
Contents lists available at ScienceDirect
Thermochimica Acta journal homepage: www.elsevier.com/locate/tca
Structural and physical studies of the Ag-rich alloys from Ag-Li system a,⁎
a
b
a
a
S. Terlicka , A. Dębski , A. Budziak , M. Zabrocki , W. Gąsior a b
T
Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 30-059, Kraków, 25, Reymonta Street, Poland Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, 152 Radzikowskiego Street, Poland
ARTICLE INFO
ABSTRACT
Keywords: Intermetallics Electrical conductivity Thermal expansion X-ray diffraction Phase diagram Ag-Li alloys
The structural and physical properties of the Ag-rich alloys from Ag-Li system (Ag90Li10, Ag80Li20, Ag70Li30, Ag60Li40, Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50) were performed with the use of the three different methods. All tested alloys were prepared from high purity metals (Ag and Li) by melting in a glove-box filled with high purity argon, with a very low concentration of impurities. The high-temperature X-ray diffraction investigations were conducted to confirm the structure of the prepared alloys. The thermal expansion measurements of the Agrich alloys were carried out by an optical, horizontal dilatometer at the temperature range from 298 to 665 K. Moreover, the electrical conductivity of investigated Ag-rich alloys was measured at room temperature. The results of X-ray diffraction phase analysis, thermal expansion and electrical conductivity measurements, obtained in these studies, may undermine the reliability of the present phase diagram of Ag-Li, which makes it necessary to verify the existing phase equilibria. Further thermodynamic and physicochemical studies of Ag-Li system are crucial to get complete data for the optimization of the thermodynamic properties and calculation of the reliable phase diagram of the Ag-Li system.
1. Introduction Development of ecological technologies, energy sources and soldering materials plays an important role in present scientific research. Currently, Ag-Li alloys with a high concentration of Li are not applied, due to a high reactivity of Li with the oxygen, nitrogen, and moisture contained in the air. On the other hand, there is a large group of silver brazing alloys which contains lithium [1]. Moreover, a small addition of silver, lithium or both is used for modification of the mechanical properties at elevated temperatures, corrosion resistance and castability of magnesium alloys for the automotive, aviation, electronics and power industries, as well as for the production of medical equipment [2–9]. One can also notice that the Ag-Li alloys are promising for energy storage as a negative electrode material in the new generation of Li-ion batteries [10,11]. Thus, the full knowledge of thermodynamics, physical and chemical properties, and also the phase diagram of the AgLi system is crucial. First measurements of the Ag-Li system were made by Pastorello [12,13], in 1931. Based on the thermal and X-ray diffraction studies [12,13] the first phase diagram with two intermetallic phases (AgLi and AgLi3) was presented. Then, in 1953-4, Freeth and Reynor [14] published a different phase diagram, based on the microstructure, X-ray diffraction and thermal analysis results. They determined the maximum
⁎
solubility of Ag in bcc-(Li) and Li in fcc-(Ag), which equalled 8 at. % in the eutectic reaction at c.a. 419 K and 39.2 at. % at 590 K, respectively. What is more, they also proposed to divide the existing in the Ag-Li system area of the phase stability of the γ-brass type into three separate phases γ1, γ2 and γ3. The range of homogeneity (at room temperature) for the γ3 phase was established between 63 and 73 at. % of Li, and for γ1 phase between 87 and 93 at. % of Li. Then, based on the available literature data, Pelton [15] proposed new version of the phase diagram of Ag-Li system, which contains seven phases: fcc-(Ag), bcc-(Li), Liquid, β(bcc_B2), γ1(AgLi2), γ2(AgLi3) and γ3(AgLi6). For calculations, Pelton [15] used not only the values presented in the Freeth and Reynor’s work [14] but also the values of the enthalpy of formation of solid fcc-(Ag) phases and liquid, gained at the temperature 623 and 1250 K by Predel et al. [16]. This phase diagram was generally accepted until the end of the last century [17]. Moreover, the authors [16] proposed the position of the liquidus and solidus curves between the liquid and fcc-(Ag) phase using the regular solution model. The other important thermodynamic properties such as the activity of Li in the liquid and solid solutions and enthalpy of mixing of Ag-Li liquid alloys were presented in [18–20]. The structure of the solid fcc-(Ag) was studied by Perlitz [21] and the lattice parameters for this phase were determined by Firth et al. [22] and Kelington et al. [23]. The short-range order parameters in the solid Ag-Li solutions were presented by Ruppersberg [24], and Migge and
Corresponding author. E-mail address: [email protected] (S. Terlicka).
https://doi.org/10.1016/j.tca.2019.01.016 Received 23 August 2018; Received in revised form 14 January 2019; Accepted 19 January 2019 Available online 31 January 2019 0040-6031/ © 2019 Elsevier B.V. All rights reserved.
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Table 1 Specifications of the applied materials. Chemical name
Source
Purity [mass.%]
Purification method
Analysis method
Lithium Silver Argon
Alfa Aesar Innovator Sp. z o.o Air Products
99.99 99.9 99.9999
None None None
Certified purity Certified purity Certified purity
Andersen [25]. First attempts to define the structure of the γ3 phase (Ag30.2Li69.8) were done by Arnberg and Westman [26,27] with the use of X-ray diffraction analysis. They found that the γ3 phase had 26 atoms in the bcc lattice (I 43m ). Noritake et al. [28] determined the γ-brass structure of Li64Ag36 alloy, by means of synchrotron powder diffraction and the Rietveld refinement. This structure coincides relatively with the phase stability of the γ3 phase. Pavlyuk et al. [29] critically analyzed the available data for Ag-Li system and proposed a new development of the phase diagram for this system, which was similar to this presented by Okamoto [17]. In the work [29] Ag-Li phase diagram contained four binary compounds β-AgLi and: γ1 (AgLi12), γ2 (Ag3Li10) and γ3 (Ag4Li9), which were closely related to each other and with the structure of the γbrass. The β-AgLi phase crystallizes in the regular structure of the CsCl type (Pm 3¯ m, a = 3.169 Å) [30,31], which transforms into the tetragonal structure of the UPb type (I41/amd) at ambient conditions [29]. This phase transformation from regular to the tetragonal structure was found by [29] with the use of X-ray diffraction and by means of SHELXS and SHELXL programs [32], and the Rietveld refinement. The lattice parameters of the tetragonal structure of AgLi phase were: a = 3.9605(1), c = 8.2825(2) Å, and factors: R = 4.81, Rf = 4.87 [29]. The first suggestion about the instability of AgLi phase was proposed by Pauly [33], who has studied the X-ray diffraction patterns of pseudobinary sections for AgLi-InLi, AgLi-AuLi and AgLi-LiTl systems. The author [33] noticed that the X-ray diffraction pattern of the ternary alloys close to the composition of the binary end-phase AgLi never reproduced the characteristic structure of the CsCl type. However, Pauly [33] suggested the existence of another undefined structure. This information inspired scientists to study the structure of an unknown phase β-AgLi. Wang et al. [34] found that the minimum value of the enthalpy of mixing of liquid Ag-Li alloys exists for XLi = 0.50, which presents a weak tendency to formation of short-range order in this solution with the maximum order in liquid phase surroundings. For the description of liquid solutions, the authors [34] used the modified quasi-chemical MQMPA model proposed by Pelton and Chartrand [35]. They also compared the calculated enthalpy of formation of solid fcc at 623 K with the Predel et al. [16] data, and the calculated activity of lithium with this measured by Becker et al. [18] at 830 K. The aim of our work was the study of the physical properties of Agrich alloys of Ag-Li system and verification of existing phase areas occurring in this binary system up to XLi = 0.50 concentration range.
The X-ray diffraction patterns of the Ag-Li alloys were performed with the use of the X’Pert PRO PANalytical diffractometer (CuKα radiation, λ = 1.50589 Å) equipped with high-temperature chamber HTK 1200 N (Anton Paar). The chamber was pumped-out continuously during studies and the pressure of gases inside the chamber was lower than 10−3 mbar. The data were collected during the heating-up samples (the heating rate: 10 K/min). At each step, the temperature was stabilized (10 min) in order to reach the thermal equilibrium. For identification of the XRD patterns, the PDF-4 database was used. The thermal expansion of the Ag90Li10, Ag80Li20, Ag70Li30, Ag60Li40, Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50 alloys was determined with an optical, horizontal dilatometer Misura® 3 FLEX-ODLT produced by Expert System Solution, using heating rates of 5 K/min for samples with the air atmosphere. This optical dilatometer allows to measure the noncontact thermomechanical behaviour of the sample without modification by the measuring system. The tested alloys were also prepared in a glove-box from the weighed amounts of pure metals, which were melted together in the heat-resistant steel (H25 T) crucible. The liquid samples were mixed and then poured into a specially designed steel ingot mold. The obtained alloys were homogenized for 24 h at 663 K. Then, they were cooled down to room temperature with a furnace. During the thermal expansion measurements, the parallelepiped specimens (dimensions of sample 50 × 5 × 5 mm) was fixed horizontally
Fig. 1. The sample inside the optical dilatometer Misura 3 FLEX-ODLT.
2. Materials and methods The samples of Ag-Li alloys for the high-temperature X-ray diffraction measurements were prepared similarly to the one described in our previous works [36]. The specifications of pure, metallic elements used in all experiments are listed in Table 1. The alloys were prepared in a glove box filled with a high purity argon atmosphere (Table 1), with a trace concentration of impurities (O2 < 0.1 ppm, N2 < 0.1 ppm, H2O < 0.1 ppm). Weighed amounts of pure metals were melted in heatresistant steel (H25 T) crucibles at temperatures higher than 50 K of the liquidus temperature. Such prepared samples were held in a glove box to protect them from reacting with the air components. Directly before each measurement, the specimens were removed from the glove box in a special holder and then, directly before the X-ray diffraction experiments, the sample was put out from the holder and put into the diffractometer.
Fig. 2. X-ray diffraction pattern of the Ag90Li10 alloy. 186
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 3. X-ray diffraction pattern of the Ag80Li20 alloy.
Fig. 5. X-ray diffraction pattern of the Ag60Li40 alloy.
between two holding rods on a sample pad in the furnace (Fig. 1). Two beams of blue light (a wavelength of 478 nm) illuminate both ends of the sample and two digital cameras capture the images. The obtained optical resolution of the device reached 0.5 μm per pixel. The temperature and expansion properties in this apparatus were calibrated with the use of Standard Reference Material 738 – Stainless Steel. It was also observed that Ag-rich alloys react with components of air by slowly forming of a very thin layer of Li-oxide, especially at the elevated temperatures. Since the used samples were very long in comparison to the thickness of the oxide layer, the influence of the forming layer for the results of dilatometric measurements was very low. The electrical conductivity of investigated Ag-rich alloys was measured using SIGMATEST 2.069 (Foerster) testing instrument. The SIGMATEST device is an eddy current conductivity tester dedicated to nonferromagnetic metals, based on the complex impedance of the measuring probe. During the measurements of the samples, the instrument automatically converts the complex impedance value to an electrical conductivity value. The diameter of the used probe was 8 × 10−3 m.
Before the measurements, the instrument was calibrated with the use of dedicated standards given by producer [37]. The samples of Ag-Li alloys were rolled at room temperature to a thickness of 0.5 mm and then the studies were done and repeated five times for each specimen at the room temperature.
Fig. 4. X-ray diffraction pattern of the Ag70Li30 alloy.
Fig. 6. X-ray diffraction pattern of the Ag57Li43 alloy.
3. Results and discussion The X-ray diffraction patterns for the prepared samples are shown in Figs. 2–10. As can be seen in Figs. 2–5 the X-ray diffraction patterns for alloys, containing from 10 to 40 at. % of Li presented only the solid solution of silver up to 493 K. These results confirmed that, at the measured range of temperature, the solid solution of silver (Ag) occurs up to c.a. 40 at. % of Li. These results are in good agreement with the phase diagram presented by Pelton [16] and they do not confirm the existence at room temperature of an Ag solid solution to 34 at. % of Li suggested by Wang et al. [34]. The X-ray diffraction pattern of the Ag57Li43 alloy shows the solid
187
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 7. X-ray diffraction pattern of the Ag55Li45.
Fig. 9. X-ray diffraction pattern of the Ag50Li50.
solution of silver (Ag) up to 643 K. Moreover, a small amount of the tetragonal structure of AgLi phase at 393 K and Li2O were detected most probably due to the fact that the X-ray diffraction measurements were carried out in the out-gassed system (p < 10−3mbar of air). In the case of X-ray diffraction of the Ag55Li45 and Ag52Li48 alloys, shown in Figs. 7–8, the solid solution of silver (Ag), AgLi intermetallic phases (both tetragonal and cubic structure) and a small amount Li2O were found. The AgLi (both tetragonal and cubic forms) is detected up to 463 K and at higher temperatures, only the cubic structure of AgLi phase is detected. The X-ray diffraction phase analysis of the Ag50Li50 alloy, presented in Fig. 9, shows that AgLi intermetallic phase exists only in a cubic structure until c.a. 535 K. Above this temperature only the solid solution of Li in silver (Ag) with a small amount Li2O was found. Furthermore, the AgLi intermetallic phase (tetragonal structure) appears only during the first series of X-ray diffraction measurements at room temperature (298 K). In the second series the tetragonal structure of AgLi phase was not observed. It may suggest that the tetragonal structure of
AgLi phase needs more time to form, and the time of the cooling process was not enough. The diffraction patterns of the Ag55Li45 and Ag50Li50 alloys at 298 K after high-temperature X-ray measurements are shown in Fig. 10. It should be noticed, that the X-ray diffraction patterns for the Ag55Li45 alloy reveal only the AgLi (tetragonal structure) phase, while the X-ray diffraction patterns for the Ag50Li50 alloy show only the AgLi (cubic structure) phase. Such differences in obtained X-ray diffraction patterns for Ag55Li45 and Ag50Li50 alloys may suggest, that AgLi phase does not show phase transformation from the regular to tetragonal structure what was suggested by [29], but may indicate that a new intermetallic phase exists in the Ag-Li system. Based on the presented studies it seems likely that the new phase of the composition very near Ag5Li4 exists. These results should be confirmed in the future by additional measurements and need to be included in the new assessments of the Ag-Li phase diagram. For the better understanding and explanation of observed X-ray results, the thermal expansion studies of the Ag-Li solid alloys were conducted. The results of these investigations are shown in Figs. 11–12. All the experiments were done in the same temperature range, it means,
Fig. 10. Comparison of the X-ray diffraction pattern of the Ag55Li45 and Ag50Li50 alloys at 298 K after high-temperature X-ray measurements.
Fig. 8. X-ray diffraction pattern of the Ag52Li48. 188
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 11. Thermal expansion of the alloys a) Ag90Li10, b) Ag80Li20, c) Ag70Li30, d) Ag60Li40, and thermal expansion of the alloys e) Ag57Li43, f) Ag55Li45, g) Ag52Li48, h) Ag50Li50 with its first differential curve.
189
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
obtained average electrical conductivity of Ag-Li alloys, presented in Table 2, the resistivity (ρ) of investigated alloys was calculated with the use of Eq. (1) and is shown in Fig. 13(b).
=
1
(1)
As it can be noticed, the electrical conductivity values decrease rapidly with increasing lithium content up to the XLi = 0.43. After that, the measured electrical properties increase with the increasing content of Li. This change in decreasing tendency in a dependence of electrical conductivity on concentration in investigated alloys can be explained by the existence of another phase (binary area) in Ag-Li system. Furthermore, the increasing values of electrical conductivity of Ag55Li45 alloy suggest that the existing phase area ((Ag)+β) presented by Freeth and Raynor [14] is not corrected. In addition, the above-mentioned behaviour, which may suggest the existence of binary area, is better visible when taking into consideration the radical change of resistivity on the composition of Ag-Li alloys presented in Fig. 13(b). 4. Conclusions In this work, structural and physical properties of the selected Agrich alloys from the Ag-Li system were investigated with the use of the X-ray diffraction, dilatometric and electric methods. The X-ray diffraction patterns for alloys which contain from 10 to 40 at. % of Li presented only the solid solution of silver up to 693 K. In the case of the X-ray diffraction pattern of the alloys, which have from 45 to 50 at. % of Li, the AgLi intermetallic phase (tetragonal and cubic) were detected. The thermal expansion values of studies alloys were obtained with the use of an optical and horizontal dilatometer at the temperature range from 298 to 665 K. These results increase linearly with the increasing concentration of Li with temperature up to the alloy containing 40 at. % of Li, and suggest no phase transitions in these materials. The alloys, which had more than XLi = 0.40 presented the nonlinearity in the dependence of thermal expansion with temperature, which corresponds to the decomposition of the AgLi phase. The electrical conductivity values decrease with the concentration of the alloys, which have from 10 to 43 at. % of Li. For the alloys containing more than 43 at. % of Li these values increase with the increasing content of Li. The resistivity of investigated Ag-Li alloys changes rapidly for Ag0.55Li0.45. These changes in the electrical properties of Ag-rich alloys can probably be attributed to the formation of another phase (binary area). The obtained results are consistent with each other, and showed, that the most recent assessment of the Ag-Li phase diagram should be verified. The occurrence of the new intermetallic phase in the Ag-Li system should be confirmed in the future by additional measurements. Further thermodynamic and structural investigations of Ag-Li system are necessary to obtain complete data for the optimization of the thermodynamic properties and the calculation of the phase equilibria of the Ag-Li system.
Fig. 12. Change of thermal expansion in the Ag-rich alloys from Ag-Li system.
from the room temperature up to 665 K (below the solidus line). As can be seen, the values of thermal expansion show the increase with the increasing Li content in investigated alloys. Moreover, Ag90Li10, Ag80Li20, Ag70Li30, and Ag60Li40 alloys (Figs. 11a-d) present the linear dependence of thermal expansion with the temperature in the measured range of temperature. On the other hand, the relationship between expansion and temperature for the Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50 alloys (Figs. 11e-h) show a clear discontinuity of the thermal expansion values with increasing temperature, which may correspond to the phase transition, as it is shown, for example, by [38,39]. These phase transitions for mentioned phases occur at different temperatures, lower for the Ag57Li43 (˜ 460–500 K), and higher for the Ag50Li50 alloys (˜ 600 K). Based on the obtained X-ray diffraction results the observed phase transitions can be identified as a decomposition of the AgLi phase, after which only the solid solution of (Ag) exists. Electrical conductivity (σ) measurements allow us to gather the information not only about the electrical conductivity of the materials, but also to determine whether the composition of the material has changed. Structure and composition changes in materials cause changes in electrical conductivity values [40]. The measured values of electrical conductivity of Ag-rich alloys from Ag-Li system are presented in Table 2. Moreover, based on the obtained values the dependence of electrical conductivity on the composition of tested alloys was determined and shown in Fig. 13(a). For more appropriate comparison, the electrical conductivity of the pure silver is also given. Based on the
Table 2 The values of electrical conductivity for investigated Ag-Li alloys (five sets of measurements). No.
Electrical conductivity σ [MS/m] Alloy
1 2 3 4 5 Average value Standard error
Ag
Ag90Li10
Ag80Li20
Ag70Li30
Ag60Li40
Ag57Li43
Ag55Li45
Ag52Li48
Ag50Li50
60.91 61.33 61.40 61.11 60.59 61.07 0.33
8.27 8.40 8.09 8.25 9.65 8.53 0.64
3.71 3.22 3.69 3.69 3.47 3.55 0.21
1.93 1.62 1.91 1.69 1.89 1.81 0.14
1.18 1.15 1.19 1.14 1.17 1.17 0.02
1.15 1.15 1.07 1.04 1.16 1.11 0.05
2.50 2.53 2.51 2.47 2.32 2.47 0.08
8.93 8.95 8.94 8.92 8.92 8.93 0.01
12.08 12.75 12.13 12.08 12.66 12.34 0.34
190
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 13. The dependence of the average values of electrical conductivity (a) and resistivity (b) on the composition of Ag-rich alloys.
Acknowledgements
[18] [19] [20] [21] [22] [23]
The work was partially supported by the Polish Ministry of Science and Higher Education in a period of the years 2013 – 2015 in the framework of Project No. IP2012 035572. The purchase of the optical dilatometer Misura® 3 FLEX-ODLT, which was used in the investigations, was financed by the European Regional Development Fund within the frames of Project POIG. 02.01.00-12-175/09.
[24] [25] [26] [27] [28]
References
[29]
[1] W. Gąsior, A. Winiowski, Arch. Metall. Mater. 57 (2012) 1087–1093. [2] C.L. Mendis, C.J. Bettles, M.A. Gibson, C.R. Hutchinson, Mater. Sci. Eng. A 435–436 (2006) 163. [3] C.L. Mendis, C.J. Bettles, M.A. Gibson, S. Gorsse, R. Hutchinson, Philos. Mag. Lett. 86 (2006) 443. [4] G. Liang, J. Alloys. Compd. 370 (2004) 123. [5] G. Ben-Hamu, D. Elizer, A. Kaya, Y.G. Na, K.S. Shin, Mater. Sci. Eng. A 435–436 (2006) 579. [6] C.L. Mendis, K. Oh-ishi, K. Hono, Scr. Mater. 57 (2007) 485. [7] H.T. Son, D.G. Kim, J.S. Park, Mater. Lett. 65 (2011) 3150. [8] S.C. Park, J.D. Lim, D. Eliezer, K.S. Shin, Mater. Sci. Forum 419–422 (2003) 159. [9] Q. Liu, Acta Metall. Sin. 46 (11) (2010) 1458–1472. [10] G. Taillades, J. Sarradin, J. Power Sources 125 (125) (2004) 199–205. [11] M.N. Obrovac, V.L. Chevrier, Chem. Rev. 114 (2014) 11444–11502. [12] S. Pastorello, Gazz. Chim. Ital. 60 (1930) 493–501. [13] S. Pastorello, Gazz. Chim. Ital. 61 (1931) 47–51. [14] W.E. Freeth, G.V. Raynor, J. Inst. Met. 82 (1954) 569–574. [15] A.D. Pelton, Bull. Alloy Phase Diagr. 7 (1986) 223–228. [16] B. Predel, G. Oehme, W. Vogelbein, Z. Metall. 69 (1978) 163–166. [17] H. Okamoto, Phase Diagram for Binary Alloys, Materials Park, Ohio ASM Internat., 2000.
[30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40]
191
W. Becker, G. Schwitzgebel, H. Ruppersberg, Z. Metall. 72 (1981) 186–190. W. Gąsior, A. Dębski, J. Chem. Thermodynamics 101 (2016) 270–277. A. Dębski, M.H. Braga, W. Gąsior, J. Chem. Thermodyn. 82 (2015) 53. H. Perlitz, Z. Kristallogr., 86, (1933) 155-158. L.D. Firth, N.H.A. Nowaira, W. Scott, J. Phys. F. (Met. Phys.) 4 (1974) L200–201. S.H. Kellington, D. Loveridge, J.M. Titman, J. Phys. D (Appl. Phys. J) 2 (1969) 1162–1163. H. Ruppersberg, Phys. Lett. 54A (1975) 151–152. H. Migge, H. Andresen, Scr. Metall. Mater. 5 (1971) 175–180. L. Arnberg, S. Westman, Acta Chem. Scand. 26 (1972) 513–517. L. Arnberg, S. Westman, Acta Chem. Scand. 26 (1972) 1748–1750. T. Noritake, M. Aoki, S. Towata, T. Takeuchi, U. Mizutani, Acta Crystallogr. B63 (2007) 726–734. V.V. Pavlyuk, G.S. Dmytriv, I.I. Tarasiuk, I.V. Chumak, H. Pauly, H. Ehrenberg, Solid State Sci. 12 (2010) 274–280. E. Zintl, G. Brauer, Z. Phys. Chem. B 20 (1933) 245–271. R. Ferro, S.G.B. Bonino, Atti Accad. Naz. Lincei, Cl. Sci. Fis. Mat. Nat. Rend. 45 (1966) 348–350. G.M. Sheldrick, SHELXS & SHELXL. Programs for Crystal Structure Solution and Refinement, University of Göttingen, Germany, 1997. H. Pauly, Faculty of Chemistry, PhD thesis Darmstadt University of Technology, 1966. J. Wang, P. Chartrand, I.-H. Jung, Calphad 50 (2015) 68–81. A.D. Pelton, P. Chartrand, Metall. Mater. Trans. A32 (2001) 1355–1360. A. Dębski, S. Terlicka, A. Budziak, W. Gąsior, J. Alloys. Compd. 732 (2018) 210–217. SIGMATEST 2.069 Software Version 3.12 Operating Instructions, Foerster, http:// www.mkckorea.com/catalog/foerster/sigmatest/Sigmatest%202.069%20Op %20Inst20v3.12%20.pdf. A.Grajcar W. Zalecki, P. Skrzypczyk, A. Kilarski, A. Kowalski, S. Kołodziej, J. Therm. Anal. Calorim. 118 (2014) 739–748. M.D. Mathews, A.K. Tyagi, P.N. Moorthy, Thermochim. Acta 298 (1997) 165–167. W.W. Hintalla, The Electrical Conductivity of the Copper-Aluminum Alloys, Bachelors Theses and Reports, 1928 –1970.
Contents lists available at ScienceDirect
Thermochimica Acta journal homepage: www.elsevier.com/locate/tca
Structural and physical studies of the Ag-rich alloys from Ag-Li system a,⁎
a
b
a
a
S. Terlicka , A. Dębski , A. Budziak , M. Zabrocki , W. Gąsior a b
T
Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 30-059, Kraków, 25, Reymonta Street, Poland Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, 152 Radzikowskiego Street, Poland
ARTICLE INFO
ABSTRACT
Keywords: Intermetallics Electrical conductivity Thermal expansion X-ray diffraction Phase diagram Ag-Li alloys
The structural and physical properties of the Ag-rich alloys from Ag-Li system (Ag90Li10, Ag80Li20, Ag70Li30, Ag60Li40, Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50) were performed with the use of the three different methods. All tested alloys were prepared from high purity metals (Ag and Li) by melting in a glove-box filled with high purity argon, with a very low concentration of impurities. The high-temperature X-ray diffraction investigations were conducted to confirm the structure of the prepared alloys. The thermal expansion measurements of the Agrich alloys were carried out by an optical, horizontal dilatometer at the temperature range from 298 to 665 K. Moreover, the electrical conductivity of investigated Ag-rich alloys was measured at room temperature. The results of X-ray diffraction phase analysis, thermal expansion and electrical conductivity measurements, obtained in these studies, may undermine the reliability of the present phase diagram of Ag-Li, which makes it necessary to verify the existing phase equilibria. Further thermodynamic and physicochemical studies of Ag-Li system are crucial to get complete data for the optimization of the thermodynamic properties and calculation of the reliable phase diagram of the Ag-Li system.
1. Introduction Development of ecological technologies, energy sources and soldering materials plays an important role in present scientific research. Currently, Ag-Li alloys with a high concentration of Li are not applied, due to a high reactivity of Li with the oxygen, nitrogen, and moisture contained in the air. On the other hand, there is a large group of silver brazing alloys which contains lithium [1]. Moreover, a small addition of silver, lithium or both is used for modification of the mechanical properties at elevated temperatures, corrosion resistance and castability of magnesium alloys for the automotive, aviation, electronics and power industries, as well as for the production of medical equipment [2–9]. One can also notice that the Ag-Li alloys are promising for energy storage as a negative electrode material in the new generation of Li-ion batteries [10,11]. Thus, the full knowledge of thermodynamics, physical and chemical properties, and also the phase diagram of the AgLi system is crucial. First measurements of the Ag-Li system were made by Pastorello [12,13], in 1931. Based on the thermal and X-ray diffraction studies [12,13] the first phase diagram with two intermetallic phases (AgLi and AgLi3) was presented. Then, in 1953-4, Freeth and Reynor [14] published a different phase diagram, based on the microstructure, X-ray diffraction and thermal analysis results. They determined the maximum
⁎
solubility of Ag in bcc-(Li) and Li in fcc-(Ag), which equalled 8 at. % in the eutectic reaction at c.a. 419 K and 39.2 at. % at 590 K, respectively. What is more, they also proposed to divide the existing in the Ag-Li system area of the phase stability of the γ-brass type into three separate phases γ1, γ2 and γ3. The range of homogeneity (at room temperature) for the γ3 phase was established between 63 and 73 at. % of Li, and for γ1 phase between 87 and 93 at. % of Li. Then, based on the available literature data, Pelton [15] proposed new version of the phase diagram of Ag-Li system, which contains seven phases: fcc-(Ag), bcc-(Li), Liquid, β(bcc_B2), γ1(AgLi2), γ2(AgLi3) and γ3(AgLi6). For calculations, Pelton [15] used not only the values presented in the Freeth and Reynor’s work [14] but also the values of the enthalpy of formation of solid fcc-(Ag) phases and liquid, gained at the temperature 623 and 1250 K by Predel et al. [16]. This phase diagram was generally accepted until the end of the last century [17]. Moreover, the authors [16] proposed the position of the liquidus and solidus curves between the liquid and fcc-(Ag) phase using the regular solution model. The other important thermodynamic properties such as the activity of Li in the liquid and solid solutions and enthalpy of mixing of Ag-Li liquid alloys were presented in [18–20]. The structure of the solid fcc-(Ag) was studied by Perlitz [21] and the lattice parameters for this phase were determined by Firth et al. [22] and Kelington et al. [23]. The short-range order parameters in the solid Ag-Li solutions were presented by Ruppersberg [24], and Migge and
Corresponding author. E-mail address: [email protected] (S. Terlicka).
https://doi.org/10.1016/j.tca.2019.01.016 Received 23 August 2018; Received in revised form 14 January 2019; Accepted 19 January 2019 Available online 31 January 2019 0040-6031/ © 2019 Elsevier B.V. All rights reserved.
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Table 1 Specifications of the applied materials. Chemical name
Source
Purity [mass.%]
Purification method
Analysis method
Lithium Silver Argon
Alfa Aesar Innovator Sp. z o.o Air Products
99.99 99.9 99.9999
None None None
Certified purity Certified purity Certified purity
Andersen [25]. First attempts to define the structure of the γ3 phase (Ag30.2Li69.8) were done by Arnberg and Westman [26,27] with the use of X-ray diffraction analysis. They found that the γ3 phase had 26 atoms in the bcc lattice (I 43m ). Noritake et al. [28] determined the γ-brass structure of Li64Ag36 alloy, by means of synchrotron powder diffraction and the Rietveld refinement. This structure coincides relatively with the phase stability of the γ3 phase. Pavlyuk et al. [29] critically analyzed the available data for Ag-Li system and proposed a new development of the phase diagram for this system, which was similar to this presented by Okamoto [17]. In the work [29] Ag-Li phase diagram contained four binary compounds β-AgLi and: γ1 (AgLi12), γ2 (Ag3Li10) and γ3 (Ag4Li9), which were closely related to each other and with the structure of the γbrass. The β-AgLi phase crystallizes in the regular structure of the CsCl type (Pm 3¯ m, a = 3.169 Å) [30,31], which transforms into the tetragonal structure of the UPb type (I41/amd) at ambient conditions [29]. This phase transformation from regular to the tetragonal structure was found by [29] with the use of X-ray diffraction and by means of SHELXS and SHELXL programs [32], and the Rietveld refinement. The lattice parameters of the tetragonal structure of AgLi phase were: a = 3.9605(1), c = 8.2825(2) Å, and factors: R = 4.81, Rf = 4.87 [29]. The first suggestion about the instability of AgLi phase was proposed by Pauly [33], who has studied the X-ray diffraction patterns of pseudobinary sections for AgLi-InLi, AgLi-AuLi and AgLi-LiTl systems. The author [33] noticed that the X-ray diffraction pattern of the ternary alloys close to the composition of the binary end-phase AgLi never reproduced the characteristic structure of the CsCl type. However, Pauly [33] suggested the existence of another undefined structure. This information inspired scientists to study the structure of an unknown phase β-AgLi. Wang et al. [34] found that the minimum value of the enthalpy of mixing of liquid Ag-Li alloys exists for XLi = 0.50, which presents a weak tendency to formation of short-range order in this solution with the maximum order in liquid phase surroundings. For the description of liquid solutions, the authors [34] used the modified quasi-chemical MQMPA model proposed by Pelton and Chartrand [35]. They also compared the calculated enthalpy of formation of solid fcc at 623 K with the Predel et al. [16] data, and the calculated activity of lithium with this measured by Becker et al. [18] at 830 K. The aim of our work was the study of the physical properties of Agrich alloys of Ag-Li system and verification of existing phase areas occurring in this binary system up to XLi = 0.50 concentration range.
The X-ray diffraction patterns of the Ag-Li alloys were performed with the use of the X’Pert PRO PANalytical diffractometer (CuKα radiation, λ = 1.50589 Å) equipped with high-temperature chamber HTK 1200 N (Anton Paar). The chamber was pumped-out continuously during studies and the pressure of gases inside the chamber was lower than 10−3 mbar. The data were collected during the heating-up samples (the heating rate: 10 K/min). At each step, the temperature was stabilized (10 min) in order to reach the thermal equilibrium. For identification of the XRD patterns, the PDF-4 database was used. The thermal expansion of the Ag90Li10, Ag80Li20, Ag70Li30, Ag60Li40, Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50 alloys was determined with an optical, horizontal dilatometer Misura® 3 FLEX-ODLT produced by Expert System Solution, using heating rates of 5 K/min for samples with the air atmosphere. This optical dilatometer allows to measure the noncontact thermomechanical behaviour of the sample without modification by the measuring system. The tested alloys were also prepared in a glove-box from the weighed amounts of pure metals, which were melted together in the heat-resistant steel (H25 T) crucible. The liquid samples were mixed and then poured into a specially designed steel ingot mold. The obtained alloys were homogenized for 24 h at 663 K. Then, they were cooled down to room temperature with a furnace. During the thermal expansion measurements, the parallelepiped specimens (dimensions of sample 50 × 5 × 5 mm) was fixed horizontally
Fig. 1. The sample inside the optical dilatometer Misura 3 FLEX-ODLT.
2. Materials and methods The samples of Ag-Li alloys for the high-temperature X-ray diffraction measurements were prepared similarly to the one described in our previous works [36]. The specifications of pure, metallic elements used in all experiments are listed in Table 1. The alloys were prepared in a glove box filled with a high purity argon atmosphere (Table 1), with a trace concentration of impurities (O2 < 0.1 ppm, N2 < 0.1 ppm, H2O < 0.1 ppm). Weighed amounts of pure metals were melted in heatresistant steel (H25 T) crucibles at temperatures higher than 50 K of the liquidus temperature. Such prepared samples were held in a glove box to protect them from reacting with the air components. Directly before each measurement, the specimens were removed from the glove box in a special holder and then, directly before the X-ray diffraction experiments, the sample was put out from the holder and put into the diffractometer.
Fig. 2. X-ray diffraction pattern of the Ag90Li10 alloy. 186
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 3. X-ray diffraction pattern of the Ag80Li20 alloy.
Fig. 5. X-ray diffraction pattern of the Ag60Li40 alloy.
between two holding rods on a sample pad in the furnace (Fig. 1). Two beams of blue light (a wavelength of 478 nm) illuminate both ends of the sample and two digital cameras capture the images. The obtained optical resolution of the device reached 0.5 μm per pixel. The temperature and expansion properties in this apparatus were calibrated with the use of Standard Reference Material 738 – Stainless Steel. It was also observed that Ag-rich alloys react with components of air by slowly forming of a very thin layer of Li-oxide, especially at the elevated temperatures. Since the used samples were very long in comparison to the thickness of the oxide layer, the influence of the forming layer for the results of dilatometric measurements was very low. The electrical conductivity of investigated Ag-rich alloys was measured using SIGMATEST 2.069 (Foerster) testing instrument. The SIGMATEST device is an eddy current conductivity tester dedicated to nonferromagnetic metals, based on the complex impedance of the measuring probe. During the measurements of the samples, the instrument automatically converts the complex impedance value to an electrical conductivity value. The diameter of the used probe was 8 × 10−3 m.
Before the measurements, the instrument was calibrated with the use of dedicated standards given by producer [37]. The samples of Ag-Li alloys were rolled at room temperature to a thickness of 0.5 mm and then the studies were done and repeated five times for each specimen at the room temperature.
Fig. 4. X-ray diffraction pattern of the Ag70Li30 alloy.
Fig. 6. X-ray diffraction pattern of the Ag57Li43 alloy.
3. Results and discussion The X-ray diffraction patterns for the prepared samples are shown in Figs. 2–10. As can be seen in Figs. 2–5 the X-ray diffraction patterns for alloys, containing from 10 to 40 at. % of Li presented only the solid solution of silver up to 493 K. These results confirmed that, at the measured range of temperature, the solid solution of silver (Ag) occurs up to c.a. 40 at. % of Li. These results are in good agreement with the phase diagram presented by Pelton [16] and they do not confirm the existence at room temperature of an Ag solid solution to 34 at. % of Li suggested by Wang et al. [34]. The X-ray diffraction pattern of the Ag57Li43 alloy shows the solid
187
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 7. X-ray diffraction pattern of the Ag55Li45.
Fig. 9. X-ray diffraction pattern of the Ag50Li50.
solution of silver (Ag) up to 643 K. Moreover, a small amount of the tetragonal structure of AgLi phase at 393 K and Li2O were detected most probably due to the fact that the X-ray diffraction measurements were carried out in the out-gassed system (p < 10−3mbar of air). In the case of X-ray diffraction of the Ag55Li45 and Ag52Li48 alloys, shown in Figs. 7–8, the solid solution of silver (Ag), AgLi intermetallic phases (both tetragonal and cubic structure) and a small amount Li2O were found. The AgLi (both tetragonal and cubic forms) is detected up to 463 K and at higher temperatures, only the cubic structure of AgLi phase is detected. The X-ray diffraction phase analysis of the Ag50Li50 alloy, presented in Fig. 9, shows that AgLi intermetallic phase exists only in a cubic structure until c.a. 535 K. Above this temperature only the solid solution of Li in silver (Ag) with a small amount Li2O was found. Furthermore, the AgLi intermetallic phase (tetragonal structure) appears only during the first series of X-ray diffraction measurements at room temperature (298 K). In the second series the tetragonal structure of AgLi phase was not observed. It may suggest that the tetragonal structure of
AgLi phase needs more time to form, and the time of the cooling process was not enough. The diffraction patterns of the Ag55Li45 and Ag50Li50 alloys at 298 K after high-temperature X-ray measurements are shown in Fig. 10. It should be noticed, that the X-ray diffraction patterns for the Ag55Li45 alloy reveal only the AgLi (tetragonal structure) phase, while the X-ray diffraction patterns for the Ag50Li50 alloy show only the AgLi (cubic structure) phase. Such differences in obtained X-ray diffraction patterns for Ag55Li45 and Ag50Li50 alloys may suggest, that AgLi phase does not show phase transformation from the regular to tetragonal structure what was suggested by [29], but may indicate that a new intermetallic phase exists in the Ag-Li system. Based on the presented studies it seems likely that the new phase of the composition very near Ag5Li4 exists. These results should be confirmed in the future by additional measurements and need to be included in the new assessments of the Ag-Li phase diagram. For the better understanding and explanation of observed X-ray results, the thermal expansion studies of the Ag-Li solid alloys were conducted. The results of these investigations are shown in Figs. 11–12. All the experiments were done in the same temperature range, it means,
Fig. 10. Comparison of the X-ray diffraction pattern of the Ag55Li45 and Ag50Li50 alloys at 298 K after high-temperature X-ray measurements.
Fig. 8. X-ray diffraction pattern of the Ag52Li48. 188
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 11. Thermal expansion of the alloys a) Ag90Li10, b) Ag80Li20, c) Ag70Li30, d) Ag60Li40, and thermal expansion of the alloys e) Ag57Li43, f) Ag55Li45, g) Ag52Li48, h) Ag50Li50 with its first differential curve.
189
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
obtained average electrical conductivity of Ag-Li alloys, presented in Table 2, the resistivity (ρ) of investigated alloys was calculated with the use of Eq. (1) and is shown in Fig. 13(b).
=
1
(1)
As it can be noticed, the electrical conductivity values decrease rapidly with increasing lithium content up to the XLi = 0.43. After that, the measured electrical properties increase with the increasing content of Li. This change in decreasing tendency in a dependence of electrical conductivity on concentration in investigated alloys can be explained by the existence of another phase (binary area) in Ag-Li system. Furthermore, the increasing values of electrical conductivity of Ag55Li45 alloy suggest that the existing phase area ((Ag)+β) presented by Freeth and Raynor [14] is not corrected. In addition, the above-mentioned behaviour, which may suggest the existence of binary area, is better visible when taking into consideration the radical change of resistivity on the composition of Ag-Li alloys presented in Fig. 13(b). 4. Conclusions In this work, structural and physical properties of the selected Agrich alloys from the Ag-Li system were investigated with the use of the X-ray diffraction, dilatometric and electric methods. The X-ray diffraction patterns for alloys which contain from 10 to 40 at. % of Li presented only the solid solution of silver up to 693 K. In the case of the X-ray diffraction pattern of the alloys, which have from 45 to 50 at. % of Li, the AgLi intermetallic phase (tetragonal and cubic) were detected. The thermal expansion values of studies alloys were obtained with the use of an optical and horizontal dilatometer at the temperature range from 298 to 665 K. These results increase linearly with the increasing concentration of Li with temperature up to the alloy containing 40 at. % of Li, and suggest no phase transitions in these materials. The alloys, which had more than XLi = 0.40 presented the nonlinearity in the dependence of thermal expansion with temperature, which corresponds to the decomposition of the AgLi phase. The electrical conductivity values decrease with the concentration of the alloys, which have from 10 to 43 at. % of Li. For the alloys containing more than 43 at. % of Li these values increase with the increasing content of Li. The resistivity of investigated Ag-Li alloys changes rapidly for Ag0.55Li0.45. These changes in the electrical properties of Ag-rich alloys can probably be attributed to the formation of another phase (binary area). The obtained results are consistent with each other, and showed, that the most recent assessment of the Ag-Li phase diagram should be verified. The occurrence of the new intermetallic phase in the Ag-Li system should be confirmed in the future by additional measurements. Further thermodynamic and structural investigations of Ag-Li system are necessary to obtain complete data for the optimization of the thermodynamic properties and the calculation of the phase equilibria of the Ag-Li system.
Fig. 12. Change of thermal expansion in the Ag-rich alloys from Ag-Li system.
from the room temperature up to 665 K (below the solidus line). As can be seen, the values of thermal expansion show the increase with the increasing Li content in investigated alloys. Moreover, Ag90Li10, Ag80Li20, Ag70Li30, and Ag60Li40 alloys (Figs. 11a-d) present the linear dependence of thermal expansion with the temperature in the measured range of temperature. On the other hand, the relationship between expansion and temperature for the Ag57Li43, Ag55Li45, Ag52Li48, and Ag50Li50 alloys (Figs. 11e-h) show a clear discontinuity of the thermal expansion values with increasing temperature, which may correspond to the phase transition, as it is shown, for example, by [38,39]. These phase transitions for mentioned phases occur at different temperatures, lower for the Ag57Li43 (˜ 460–500 K), and higher for the Ag50Li50 alloys (˜ 600 K). Based on the obtained X-ray diffraction results the observed phase transitions can be identified as a decomposition of the AgLi phase, after which only the solid solution of (Ag) exists. Electrical conductivity (σ) measurements allow us to gather the information not only about the electrical conductivity of the materials, but also to determine whether the composition of the material has changed. Structure and composition changes in materials cause changes in electrical conductivity values [40]. The measured values of electrical conductivity of Ag-rich alloys from Ag-Li system are presented in Table 2. Moreover, based on the obtained values the dependence of electrical conductivity on the composition of tested alloys was determined and shown in Fig. 13(a). For more appropriate comparison, the electrical conductivity of the pure silver is also given. Based on the
Table 2 The values of electrical conductivity for investigated Ag-Li alloys (five sets of measurements). No.
Electrical conductivity σ [MS/m] Alloy
1 2 3 4 5 Average value Standard error
Ag
Ag90Li10
Ag80Li20
Ag70Li30
Ag60Li40
Ag57Li43
Ag55Li45
Ag52Li48
Ag50Li50
60.91 61.33 61.40 61.11 60.59 61.07 0.33
8.27 8.40 8.09 8.25 9.65 8.53 0.64
3.71 3.22 3.69 3.69 3.47 3.55 0.21
1.93 1.62 1.91 1.69 1.89 1.81 0.14
1.18 1.15 1.19 1.14 1.17 1.17 0.02
1.15 1.15 1.07 1.04 1.16 1.11 0.05
2.50 2.53 2.51 2.47 2.32 2.47 0.08
8.93 8.95 8.94 8.92 8.92 8.93 0.01
12.08 12.75 12.13 12.08 12.66 12.34 0.34
190
Thermochimica Acta 673 (2019) 185–191
S. Terlicka et al.
Fig. 13. The dependence of the average values of electrical conductivity (a) and resistivity (b) on the composition of Ag-rich alloys.
Acknowledgements
[18] [19] [20] [21] [22] [23]
The work was partially supported by the Polish Ministry of Science and Higher Education in a period of the years 2013 – 2015 in the framework of Project No. IP2012 035572. The purchase of the optical dilatometer Misura® 3 FLEX-ODLT, which was used in the investigations, was financed by the European Regional Development Fund within the frames of Project POIG. 02.01.00-12-175/09.
[24] [25] [26] [27] [28]
References
[29]
[1] W. Gąsior, A. Winiowski, Arch. Metall. Mater. 57 (2012) 1087–1093. [2] C.L. Mendis, C.J. Bettles, M.A. Gibson, C.R. Hutchinson, Mater. Sci. Eng. A 435–436 (2006) 163. [3] C.L. Mendis, C.J. Bettles, M.A. Gibson, S. Gorsse, R. Hutchinson, Philos. Mag. Lett. 86 (2006) 443. [4] G. Liang, J. Alloys. Compd. 370 (2004) 123. [5] G. Ben-Hamu, D. Elizer, A. Kaya, Y.G. Na, K.S. Shin, Mater. Sci. Eng. A 435–436 (2006) 579. [6] C.L. Mendis, K. Oh-ishi, K. Hono, Scr. Mater. 57 (2007) 485. [7] H.T. Son, D.G. Kim, J.S. Park, Mater. Lett. 65 (2011) 3150. [8] S.C. Park, J.D. Lim, D. Eliezer, K.S. Shin, Mater. Sci. Forum 419–422 (2003) 159. [9] Q. Liu, Acta Metall. Sin. 46 (11) (2010) 1458–1472. [10] G. Taillades, J. Sarradin, J. Power Sources 125 (125) (2004) 199–205. [11] M.N. Obrovac, V.L. Chevrier, Chem. Rev. 114 (2014) 11444–11502. [12] S. Pastorello, Gazz. Chim. Ital. 60 (1930) 493–501. [13] S. Pastorello, Gazz. Chim. Ital. 61 (1931) 47–51. [14] W.E. Freeth, G.V. Raynor, J. Inst. Met. 82 (1954) 569–574. [15] A.D. Pelton, Bull. Alloy Phase Diagr. 7 (1986) 223–228. [16] B. Predel, G. Oehme, W. Vogelbein, Z. Metall. 69 (1978) 163–166. [17] H. Okamoto, Phase Diagram for Binary Alloys, Materials Park, Ohio ASM Internat., 2000.
[30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40]
191
W. Becker, G. Schwitzgebel, H. Ruppersberg, Z. Metall. 72 (1981) 186–190. W. Gąsior, A. Dębski, J. Chem. Thermodynamics 101 (2016) 270–277. A. Dębski, M.H. Braga, W. Gąsior, J. Chem. Thermodyn. 82 (2015) 53. H. Perlitz, Z. Kristallogr., 86, (1933) 155-158. L.D. Firth, N.H.A. Nowaira, W. Scott, J. Phys. F. (Met. Phys.) 4 (1974) L200–201. S.H. Kellington, D. Loveridge, J.M. Titman, J. Phys. D (Appl. Phys. J) 2 (1969) 1162–1163. H. Ruppersberg, Phys. Lett. 54A (1975) 151–152. H. Migge, H. Andresen, Scr. Metall. Mater. 5 (1971) 175–180. L. Arnberg, S. Westman, Acta Chem. Scand. 26 (1972) 513–517. L. Arnberg, S. Westman, Acta Chem. Scand. 26 (1972) 1748–1750. T. Noritake, M. Aoki, S. Towata, T. Takeuchi, U. Mizutani, Acta Crystallogr. B63 (2007) 726–734. V.V. Pavlyuk, G.S. Dmytriv, I.I. Tarasiuk, I.V. Chumak, H. Pauly, H. Ehrenberg, Solid State Sci. 12 (2010) 274–280. E. Zintl, G. Brauer, Z. Phys. Chem. B 20 (1933) 245–271. R. Ferro, S.G.B. Bonino, Atti Accad. Naz. Lincei, Cl. Sci. Fis. Mat. Nat. Rend. 45 (1966) 348–350. G.M. Sheldrick, SHELXS & SHELXL. Programs for Crystal Structure Solution and Refinement, University of Göttingen, Germany, 1997. H. Pauly, Faculty of Chemistry, PhD thesis Darmstadt University of Technology, 1966. J. Wang, P. Chartrand, I.-H. Jung, Calphad 50 (2015) 68–81. A.D. Pelton, P. Chartrand, Metall. Mater. Trans. A32 (2001) 1355–1360. A. Dębski, S. Terlicka, A. Budziak, W. Gąsior, J. Alloys. Compd. 732 (2018) 210–217. SIGMATEST 2.069 Software Version 3.12 Operating Instructions, Foerster, http:// www.mkckorea.com/catalog/foerster/sigmatest/Sigmatest%202.069%20Op %20Inst20v3.12%20.pdf. A.Grajcar W. Zalecki, P. Skrzypczyk, A. Kilarski, A. Kowalski, S. Kołodziej, J. Therm. Anal. Calorim. 118 (2014) 739–748. M.D. Mathews, A.K. Tyagi, P.N. Moorthy, Thermochim. Acta 298 (1997) 165–167. W.W. Hintalla, The Electrical Conductivity of the Copper-Aluminum Alloys, Bachelors Theses and Reports, 1928 –1970.