Study of the In–S phase diagram using spectrophotometric characterization of equilibria between hydrogen and indium sulfides

• We investigated the In–S phase diagram with the method of ancillary component (H2).
• In6S7, In3−xS4 and In2S3 (low-temp.) can be studied through our P–T and KP#–T data.
• The homogeneity range of spinel-type phase In3−xS4 is relatively broad.
• The spinel-type phase In3−xS4 has a tendency to decompose into independent phases.
• We found a narrow two-phase field between In3−xS4 and low-temperature phase In2S3.

We have developed and put in practice a spectrophotometric procedure for hydrogen sulfide determination to study the phase diagram of the In–S system using hydrogen as an auxiliary component. Elemental analysis of the hydrogen-containing vapor phase allows the principal thermodynamic properties of the indium sulfides in equilibrium with the vapor phase to be assessed in wide temperature and composition ranges. Our results confirm the existence of a narrow two-phase field between In3−xS4 and In2S3′ (low-temperature phase), which is bounded from above by the peritectic decomposition temperature of In2S3′ (about 415 °C). We have determined the temperature-dependent sulfur (S2) vapor pressure over condensed indium sulfides. For the equilibria studied in greatest detail, the present results correlate well with mass spectrometry data for indium sulfides.