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Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong.

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Presentation on theme: "Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong."— Presentation transcript:

1 Thermodynamic assessment of Au-Sn-X (X=Co, La, Er) Ternary systems Hongqun Dong

2 Thermodynamic Description of Au-Sn-Co Ternary systems

3 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).

4 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

5 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

6 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.

7 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.

8  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.

9 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 AuSn (measured) (modified) AuSn PdSn 4 - type, AuSn reference states : Au(fcc), Sn(bct) and Co(hcp)

10 Au-Co-Sn Au-Sn binary system--improved

11 Au-Co-Sn Co-Sn binary system--modified

12 Au-Co binary system--reassessed Au-Co-Sn Invariant reactionComposition (at.%Co)T/KReference L → Au+αCo Okamoto et al This work aCo → Au+εCo Okamoto et al This work

13 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

14 Au-Co-Sn isothermal section 380 ℃ isothermal section at 396 ℃

15 Au-Co-Sn liquidus projection of Au-Sn-Co ternary system partial liquidus projection of Au-Sn-Co ternary system

16 Au-Co-Sn TypeReactionT/K U1U1 L+CoSn↔βCo 3 Sn 2 +AuSn781.4 U2U2 L+αCo↔βCo 3 Sn 2 +εCo696.7 U3U3 L+CoSn↔CoSn 2 +τ U4U4 L +εCo ↔ζ +βCo 3 Sn U5U5 L +βCo 3 Sn 2 ↔AuSn+ζ577.0 U6U6 L+AuSn↔τ1+AuSn U7U7 L+τ1↔AuSn 2 +CoSn U8U8 L+AuSn 2 ↔CoSn 2 +AuSn U9U9 L+ CoSn 2 ↔CoSn 3 +AuSn E1E1 L↔Au+αCo+ζ761.5 E2E2 L↔CoSn 3 +AuSn 4 +βSn483.0 P1P1 L+Au+β↔ζ795.1 P2P2 L+αCo+ζ↔εCo697.1 P3P3 L+AuSn+CoSn↔τ1667.9

17 Au-Co-Sn vertical section across the E2 point of Au-Sn-Co ternary system

18 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

19 Thermodynamic Description of Au-Er and Au-La binary systems

20 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 K Wu et.al formation enthalpy of IMCs -- √ Gschneidner et. al assessment √ √

21 Au-La Binary Alloy Phase Diagrams

22 Au-La reactionT/K L + Au 51 Pr 14 ↔Au 6 Pr L↔Au 6 Pr + Au(fcc) L + Au 51 Pm 14 ↔Au 6 Pm L↔Au 6 Pm + Au(fcc) L + Au 51 Nd 14 ↔Au 6 Nd L↔Au 6 Nd + Au(fcc) L + Au 51 Sm 14 ↔Au 6 Sm L↔Au 6 Sm+ Au(fcc) L + Au 51 Dy 14 ↔Au 6 Dy L↔Au 6 Dy + Au(fcc) L + Au 51 Gd 14 ↔Au 6 Gd--- L↔Au 6 Gd + Au(fcc) L + Au 51 Tb 14 ↔Au 6 Tb L↔Au 6 Tb+ Au(fcc) Temperature of invariant reactions involving Au 6 La phase are 1173K and 1063K, respectively

23 Au-Er Binary Alloy Phase Diagrams A.Saccone, D. Maccio, Intemetallics, 10(2002)903

24 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.

25 phaseAb initio, this work, (kJ/mol) Meschel (±1.9) (kJ/mol) Alqasmi (kJ/mol) AuLa  AuLa βAuLa Au 2 La Au 51 La AuLa AuEr αAuEr βAuEr Au 10 Er Au 2 Er Au 3 Er Au 4 Er Results and discussion The comparison between calculated formation enthalpies of IMCs and experimental outcomes, reference states: Au(fcc), La(dhcp), Er(fcc)

26 Au-Er Calculated phase diagram compared to experimental results

27 Au-Er Reference states : Au(fcc), Er(hcp)

28 Au-La Calculated phase diagram compared with outcomes of Gshneidner

29 Au-La Reference states: Au(fcc), La(dhcp) Reference states: Au(Liquid), La(Liquid)

30 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

31 Au-Sn-La Vertical section across the E1 eutectic point of the Au-Sn-La ternary system

32 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.

33 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

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36 isothermal section at 394 ℃


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