CuS₄Y₅
sulfide metal composite · sulfide low tempCu1S4Y5 is a sulfide metal composite suitable as sulfide low temp. Color: green-red-copper. Fired at 130°C from 3 precursors (Y2O3, S, CuO). Workshop batch: 300g at €9.79. Compressive strength ~350 MPa; estimated 0.09 kg CO₂/kg (-89% vs Portland cement). Notable: forms without a kiln. Confidence: medium.
- forms at
- 130 °C · hotplate · no kiln
- replaces
- portland cement
- CO₂
- 89.1% lower than Portland cement (0.09 vs 0.83 kg CO₂/kg)
- energy
- 89.1% lower than Portland cement (0.60 vs 5.50 MJ/kg)
- compressive
- 350 MPa
- density
- 4.88 g/cm³
- crystal
- tetragonal
- band gap
- 0.01 eV
- cost
- €32.63/kg · €9.79 / 300 g batch
- confidence
- medium (synthesis route)
- potential
- 0.80 · env 1.00 · novel 1.00 · struct 0.70 · lineage 0.50 · supply 0.46
- flags
- zero kiln: Forming happens without firing — the material cures through chemistry at ambient or hotplate temperature. At building scale this removes the kiln from the supply chain: on-site casting, regional workshops, cold-country fabrication all become available.
Architectural potential
A yttrium-heavy cousin to the atlas's flagship zero-kiln sulfide, cast at 130 °C on a hotplate and reaching 350 MPa of compressive strength with an eighty-nine-per-cent cut in embodied CO₂ against Portland cement. The architectural reach is the detail and tile register: drop-cast thick tiles for exhibition floors, inlay panels for gallery thresholds, sill plates and window-seat slabs in retrofit carpentry, and cast laminates bonded to timber sub-floors in workshops with no kiln access. The cement comparison carries the argument for the client — the same compressive presence, the same geological weight underfoot — with the firing removed from the supply chain entirely. Against the copper-manganese-sodium sibling from the same family, the yttrium chemistry pulls the body paler and firmer; the slab reads closer to a pale-green hearth stone than to the saturated copper-red of the reference piece. Natural placements therefore include healthcare and laboratory thresholds where a cooler colour register is wanted alongside the compression. The caveat is cut-work hygiene: sawing the cured body releases sulphide odour, so fabrication needs bench extraction, and the 300 g workshop batch puts specification firmly in the single-element register rather than bulk floor-work.
Material character
The slab reads a muted green-red copper — yttrium's pale silicate matrix dilutes the copper-red face into a warmer sage, with red emerging only where shadow deepens the body. At 4.88 g/cm³ and 85×85×28 mm the slab sits firmly two-handed on the bench, a distinct step heavier than a comparable fired-brick tile of the same face. Surface mold-matte with the cast meniscus sheen along one long edge; edges as-cast, lightly reflective where the mold wall polished the face. A fine α-sulfur bloom crystallises across the top, pale enough to read as a dusting rather than a skin. Quieter in the hand than the Cu3Mn1Na2S4 flagship — same family, cooler voice.
Recipe
300 g batch · peak 130 °C| element | precursor | formula | mass | safety |
|---|---|---|---|---|
| Cu | copper(II) oxide (black) | CuO | 12.35 g | safe |
| Y | yttrium oxide | Y2O3 | 87.65 g | moderate |
- Pre-heatHotplate to 150 °C
- MeltSulfur liquefies at 115 °C; full liquid at 130 °C
- CastPour at 140–145 °C
- SetRoom temperature 30 min (firm) → 24 h (full strength)
Zero-kiln process — 130 °C hotplate cast only