The equilibrium potentials for Sn-Na alloy formation reactions are investigated in an intermediate temperature ionic liquid, NaFSA-KFSA (x(NaFSA) = 0.56, x(KFSA) = 0.44, FSA = bis(fluorosulfonyl)amides), at 363 K. Galvanostatic intermittent titration technique (GITT) is employed to obtain the potential-Na composition curve of the Sn-Na alloy. Ex situ X-ray diffraction (XRD) analysis reveals that plateaus at 0.16 and 0.08 V vs. Na+/Na in the potential-Na composition curve correspond to alpha-NaSn/Na9Sn4 and Na9Sn4/Na15Sn4 two-phase states, respectively. Although distinct potential plateaus are not observed, the equilibrium potentials of beta-Sn/NaSn2 and NaSn2/alpha-NaSn are suggested to be 0.53 and 0.46 V vs. Na+/Na, respectively. Finally, the Gibbs free energies of formation of the Sn-Na alloys are calculated and compared with reported data. (C) 2013 Elsevier B.V. All rights reserved.