What does this research mean for the field?

The Cu-Sn-S system has been completely described for the first time, detailing the phase equilibria and identifying multiple ternary solid phases and miscibility gaps. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This research aims to elucidate the phase equilibria of the Cu-Sn-S system, which is critical for electronic applications and material recycling.

March 13, 2026Open Access

The experimental phase equilibria studies of the Cu-Sn-S system

Key Points

This research aims to elucidate the phase equilibria of the Cu-Sn-S system, which is critical for electronic applications and material recycling.
Equilibrated mixtures at temperatures ranging from 500-1300℃.
Conducted open- and closed-system experiments to explore the miscibility gap.
Utilized electron probe microanalyzer to analyze quenched samples.
Constructed liquidus and solidus projections along with isotherms for phase fields.
Identified multiple phases, including Cu 2-x S and Cu 4 SnS 4, showing specific melting behaviors.
Discovered two miscibility gaps extending from Cu-S to Sn-S binary systems.
Determined 19 invariant points and 5 saddle points in the system.
Phases were stable under pressures from 1 atmosphere to over 10 atmospheres.

Abstract

The Cu-Sn-S system applies to describe the chemistry of electronic components, low-high-grade minerals, energy storage devices, slag, solders, brass, lead bullion, flue dust, black copper, etc. Its phase equilibria are essential for modeling complex Cu-Sb-Sn-Ni-S-Fe-As matte, speiss, and metal phases. Mixtures were equilibrated at 500-1300℃, quenched in brine, and analyzed by an electron probe microanalyzer. Open- and closed-system experiments of the Cu-S and Cu-Sn-S systems revealed the miscibility gap. Liquidus and solidus projections, isotherms, and primary phase fields of each phase were constructed. Identified phases include matte, liquid metal, Cu 2- x S, SnS, Sn 2 S 3 , SnS 2 , Cu 3 Sn, Cu 4 SnS 4 (550-800℃), Cu 2 SnS 3 (600-900℃), and Cu 2 Sn 3 S 7 (700-800℃) phases. A sub-solidus inconclusive solid-solution phase was discovered at 500-650℃. Cu 4 SnS 4 and Cu 2 SnS 3 melt congruently, while Cu 2 Sn 3 S 7 shows uncertain melting behaviour. All ternary solid phases, except the inconclusive phase, form only above atmospheric pressure, with primary phase-field stability extending from 1 atmosphere to > 10 atmospheres. Nineteen invariant points and five saddle points were identified. Sn distribution between matte and liquid metal was investigated to support sustainable Sn removal during recycling of complex feedstocks. The CuS 0.5 -SnS quasi-binary and CuS 0.5 -SnS 1.5 pseudo-binary systems were also evaluated. • First time, the complete description of the Cu-Sn-S system was reported. • Studied both liquidus and solidus projections. • Contains Cu 4 SnS 4 (congruent), Cu 2 SnS 3 (congruent), and Cu 2 Sn 3 S 7 (congruently) ternary solid phases at the projection. • Cu 2 SnS 3 is solid solution. • Two miscibility gaps spread from the Cu-S binary system to the Sn-S binary system over an entire compositional range of the Cu-Sn binary in the Cu-Sn-S system. • Determined the invariant reaction types and temperature maxima. • This diagram will be used by both academic and industries to extract the Cu and Sn metals, simultaneously.

The experimental phase equilibria studies of the Cu-Sn-S system

Key Points

Abstract

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