Ca₂LaNdO₁₂V₄

Architectural potential

A rare-earth ceramic with a thermochromic vanadium-dioxide overlay: above sixty-eight degrees celsius the V-site flips and the body darkens visibly, returning below that threshold. The lanthanum-neodymium pair gives the body a colder, more mineral blue than the strontium variants and deepens the contrast between the two thermal states. This is a self-sensing passive tile — no wiring, no driver — and its architectural argument is that a single small-area element replaces a wiring-plus-sensor-plus-shading assembly. Natural placements are south-facing greenhouse glazing inserts where the tile darkens through the midday hours and clears at evening, rooftop skylight perimeter tiles that signal solar-gain events to occupants below, and atrium ceiling patches in gallery roofs where the state-shift becomes part of the diurnal spatial reading. Compression at 100 MPa keeps the material firmly in the overlay register. The three-hundred-per-cent CO₂ cost against clay brick means the piece is bought for the behaviour, not for volume — it is a small-area passive sensor carried in ceramic form. The caveat is rarity and scale: €10.36 per 100 g batch, 300 g workshop maximum, supply-chain score near zero, and untested at repeated-tile scale in architectural production. Specification belongs to prototype solar-control tile arrays and one-off pavilion work.

Material character

At room temperature the body reads a cool grey-blue with a faint mauve cast from the neodymium — a mineral blue, closer to slate than to cobalt, distinct from the vanadium-titanate blues elsewhere in the palette. At 5.29 g/cm³ and 70×70×39 mm the slab handles with rare-earth heaviness for its small footprint, a firm two-finger lift. Surface finishes sintered matte from the 1200 °C hold, the grain fine and even; edges cold-cut with diamond-saw kerf along the arris. Past the 68 °C transition the face darkens to a near-charcoal slate, uniformly across the body, with no patchiness at the phase boundary.