Presentation on theme: "Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong."— Presentation transcript:
Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong
Thermodynamic Description of Au-Sn-Co Ternary systems
Experimental Information— Au-Co ResearchersT(K) (Au) (Co) HMRMethods Taskinen1573√√electromotive force measurements and calorimetry Topor et al1378√calorimetry Predel et al1373√calorimetry Berezutsky et al1623√√measuring the vapor pressure Kubik et al 1150√electromotive force measurements Wang et al 1573 √( more negative ) studying equilibrium with CoO by using a CO/CO2 gas mixture of known partial pressure Taskinen1150√electromotive force measurements Experimental data of phase boundary are adequate, phase diagram has been assessed by Okamoto et al (in 1985) and Korb (in 2004).
Au-Co-Sn Au-SnCo-Sn H.S. Liu, C.L. Liu, K. Ishida, and Z.P. Jin, J. Electr. Mater. 32(2003)1290 M. Jiang, J. Sato, I. Ohnuma, R. Kainuma, and K. Ishida, Comp. Coup. Phase Dia. Thermoch. 28 (2004) 213–220
Au-Co-Sn Isothermal section of Au-Sn-Co system at 380 ℃ A. Neumann, A. Kjekshus, C. Rø mming, and E. Rø st, J. Alloy. Compound. 240(1996)42-50
Thermodynamic Model All of the solution phases are described as substitutional solution model; Ternary compound t1 and binary phases without third component solubility are treated as line compound. Their Gibbs energy can be described by Neumann-Kopp rule.
Binary compounds with third component solubility AuSn phase has a maximum Co content up to 12 at%, but the homogeneity range for Sn is unaffected by Co content. So a two-sublattice model (Au, Co): Sn is addopted, the Gibbs energy is formulated as: is the Gibbs energy of assumed compound CoSn. is directly cited from the report of H.S. Liu et al.
Co 3 Sn 2 phase has an extended ternary range of homogeneity (up to 23 at. % Au), and almost parallels the Au-Co boundary. Which means that the Co site in the lattice will be partially taken up by Au atoms. So, combining with the work of Jiang et al, a four- sublattice model is employed, i.e. (Au, Co) 1 : (Sn) 1 : (Co, Va) 0.5 : (Co, Va) 0.5. The Gibbs energy is expressed as :,, and are the data reported by Jiang et al.
Results and Discussions Au-Co-Sn compound Experiment ， (kJ/mol) at 78K Ab initio, this work, 0K (kJ/mol) Assessed, this work, 10K (kJ/mol) NiAs -type CoSn--3.82-3.75 AuSn -14.88 (measured) -15.69(modified) -18.77-15.75 AuSn 2 --13.10-13.38 PdSn 4 - type, AuSn 4 --7.19-7.20 reference states ： Au(fcc), Sn(bct) and Co(hcp)
Au-Co binary system--reassessed Au-Co-Sn Invariant reactionComposition (at.%Co)T/KReference L → Au+αCo24.82398.11269.5Okamoto et al. 26.220.897.71270.4This work aCo → Au+εCo99.950.2-695Okamoto et al. 99.90.999.93694This work
Au-Co-Sn The thermodynamic quantities of Au-Co binary system Reference states: Au(liquid), Co(fcc) Reference states: Au(liquid), Co(liquid) Reference states: Au(liquid), Co(fcc) at 1573K and 1623K, Au(fcc), Co(fcc) at 1150K
Au-Co-Sn vertical section across the E2 point of Au-Sn-Co ternary system
Section Summary The complete phase diagram of Au-Sn-Co ternary system is built by TC, Pandat and VASP software; The optimized parameters can reproduced most of the experimental results; The present outcomes can provide theory instruction for predicting the formation of IMCs and designing a new-type of 10Au-Sn solder. Au-Co-Sn
Thermodynamic Description of Au-Er and Au-La binary systems
Experimental information Au-La Au-Er Canneri partial phase relation √ -- Rider et. al solubility in Au √ √ McMasters crystal structure √ √ Saccone et. al entire phase relation -- √ Fitzner et. al mixing enthalpy of liquid 1473K -- Meschel et. al standard formation enthalpy Au 51 La 14 AuEr 、 Au 2 Er 、 Au 3 Er Alqsmmi formation enthalpy of IMCs -- 1073K Wu et.al formation enthalpy of IMCs -- √ Gschneidner et. al assessment √ √
Au-La reactionT/K L + Au 51 Pr 14 ↔Au 6 Pr1173.0 L↔Au 6 Pr + Au(fcc)1063.0 L + Au 51 Pm 14 ↔Au 6 Pm1180.0 L↔Au 6 Pm + Au(fcc)1104.0 L + Au 51 Nd 14 ↔Au 6 Nd1116.0 L↔Au 6 Nd + Au(fcc)1069.0 L + Au 51 Sm 14 ↔Au 6 Sm1073.0 L↔Au 6 Sm+ Au(fcc)1043.0 L + Au 51 Dy 14 ↔Au 6 Dy1118.0 L↔Au 6 Dy + Au(fcc)1081.0 L + Au 51 Gd 14 ↔Au 6 Gd--- L↔Au 6 Gd + Au(fcc)1082.0 L + Au 51 Tb 14 ↔Au 6 Tb1130.0 L↔Au 6 Tb+ Au(fcc)1071.0 Temperature of invariant reactions involving Au 6 La phase are 1173K and 1063K, respectively
Thermodynamic model Au-RE Solution phases were described as substitutional solution model; All of the IMCs were treated as line compound, their gibbs energy can be describe as Neumann–Kopp rule.
phaseAb initio, this work, (kJ/mol) Meschel (±1.9) (kJ/mol) Alqasmi (kJ/mol) AuLa 2 -56.6--- AuLa -82.0--- βAuLa-82.5--- Au 2 La-81.5--- Au 51 La 14 ----57.9--- AuLa 6 -45.1--- AuEr 2 -67.0--- αAuEr-90.9-90.2--- βAuEr-88.6----85.1 Au 10 Er 7 --- Au 2 Er-88.4-85.9-79.0 Au 3 Er-73.0-66.1-65.9 Au 4 Er-60.3--- Results and discussion The comparison between calculated formation enthalpies of IMCs and experimental outcomes, reference states: Au(fcc), La(dhcp), Er(fcc)
Au-Er Calculated phase diagram compared to experimental results
Au-Sn-La extrapolated Liquidus projection of the Au-Sn-La ternary system E1: L↔Au6La + AuSn +β T=555.5K E3: L↔LaSn3 + AuSn4 +βSn T=483K
Au-Sn-La Vertical section across the E1 eutectic point of the Au-Sn-La ternary system
Au-RE Section Summary With the calculated formation enthalpies of IMCs using ab initio approach, the Au-Er and Au-La binary systems were thermodynamic optimized by CALPHAD technique; the calculated outcomes fit well with the experimental data; the present work can theoretically guide the designing of new Au-based solder.
outlooks The experimental information of Au-RE and Sn-RE systems should be further investigated; On the basis of measured phase diagram and thermodynamic quantities, by applying CALPHAD approach to build a more compatible database of Au-Sn-RE systems, and then guide to find the proper candidates of solder alloying elements