Fe₄O₈SbV

Architectural potential

An iron-oxide ceramic with antimony and vanadium as functional modifiers, fired at 1100 °C to 100 MPa at 5.12 g/cm³, carrying a thermochromic vanadium-dioxide chemistry that flips the body's optical state at 68 °C. The load-bearing register is nominal at 100 MPa — this is not a block-work candidate — so the placements follow the thermochromic flag. Natural use is as a south-facing cladding tile on warm-toned brick façades where the body darkens visibly through the hottest afternoon hours and clears as evening cools, as a roof-tile insert over south-facing sun-rooms where summer over-heating is a live problem, and as a perimeter band around skylights in conservatories and double-skin façades that reads its own heat. Against clay brick the carbon trade is more than two-and-a-half-times negative, so the thermochromic capability has to earn the specification on its own — the building is buying self-regulation, not bulk. The amber-brown iron-oxide base colour suits warm brickwork and terracotta contexts rather than cool stone palettes. The caveat is supply: a supply-chain score of zero on antimony-vanadium-iron triples, 1100 °C peak, and a 1 kg batch-to-5 kg ceiling that allows a pattern band across a modest façade but not a full envelope.

Material character

Warm amber-brown through the 40 mm depth — iron-oxide matrix saturated to a terracotta register, with the faint tin-grey undertone that antimony brings into the matrix under shadow. At 5.12 g/cm³ and 70×70×40 mm the slab sits two-handed on the bench, denser than an ordinary fired-earthenware tile of the same face and closer in hand to a fired stoneware paver. Skin vitrified matte from the 1100 °C fire, edging into a partial glaze on the upper rim where the vanadium fraction concentrates during cooling. Edges cold-cut, kerf powder-ochre. Fully opaque. Above 68 °C the face shifts to a darker near-black state as the vanadium-dioxide transition completes — the photographic record wants the paired thermal shot alongside the ambient frame.