La₈O₂₄TeW₃

Architectural potential

A lanthanum-tungstate heavy oxide in the thermal-mass register, absorbing daytime solar gain and releasing it slowly after dark. At 100 MPa and 6.54 g/cm³ it is serious mass in a small volume, and the electrochromic tungstate chemistry adds a secondary switch: the tungsten sub-matrix shifts tint under a small DC bias, giving the piece a second life as a dimmable thermal-storage face. Natural placements are south-facing trombe-wall inserts in passive-solar hybrids, hypocaust-style floor patches under glazed loggias, radiant-heat storage panels along interior masonry walls, and switchable thermal-face tiles along atrium perimeters. The architectural argument is temporal: the slab shifts the thermal day later into the evening, smoothing the cooling load. But the embodied-CO₂ penalty is prohibitive for any volume work — three hundred and twenty-six per cent against clay brick — so specification is strictly signature-patch scale. Natural building types are retrofit passive-solar residences, winter-garden interiors, and small ritual rooms where the shifting thermal register is wanted as an architectural effect. The caveat is cost and supply chain: €31.60 per 200 g, supply-chain score of zero for the lanthanum-tungsten pair, and a 500 g workshop ceiling keeping pieces firmly in the tile register rather than wall-element.

Material character

The 70×70×31 mm slab reads a neutral warm grey at room temperature, the body sitting between sintered porcelain and a dense industrial ceramic in surface feel. At 6.54 g/cm³ the piece is strikingly heavy for its tile-scale footprint — a firm two-hand lift, closer in register to a cast-iron paperweight than to a fired tile. Surface fires to a smooth sintered matte; edges cold-cut with the diamond-saw dust along the kerf. Against an ordinary clay-brick sibling the La-W body reads almost twice the weight at the same volume, and the room-temperature colour carries a faint tungsten-blue undertone that deepens under the electrochromic bias.