Abstract: The activities of In in two pseudo-binary systems of fixed molar fraction ratio N_(Bi)/N_(Ti) have been measured by means of EMF method using zirconia solid electrolyte gal- vanic cells over the temperature range of 973—1223 K.The excess free energies were deter- mined based on the experimental data.The experimentally determined thermodynamic prop- erties of the ternary alloys agree well with the values caleulated from the author's equations using related binary data.The excess free energies are negative in almost all compositions ex- cept those near the In-Tl side and become negatively larger as the compositions approach the Bi-Tl side.

Key words: In-Bi-Tl alloy, activity, ZrO_2 solid electrolyte, excessfree energy