The CoNb2O6 pigments for brilliant-blue ceramic decoration at high temperatures over 1273 K

To date, brilliant-blue pigments that can maintain outstanding stability in a corrosive environment over 1273 K are still very desirable in the ceramic industry. We systematically investigated the structural, optical, colorimetric and thermal properties of a novel type of CoNb₂O₆ pigments, which have the 6-fold coordinated Co²⁺ as chromophores and high-valent Nb⁵⁺ as the mainstay factor for structural stabilization. Effective coloring contribution from different visible-light regions, the coloration mechanism and thermal stability of the pigments applied in glaze at 1273–1473 K are revealed for the first time. The Co²⁺ cation at the distorted [CoO₆] octahedra generates the brilliant blue hue, which can maintain the absolute blueness values, b*, at 30–44 even after glaze calcination at 1273–1423 K. The superb thermal performance in a harsh environment of the CoNb₂O₆ pigments significantly outperforms the classic CoAl₂O₄ blue, thereby exhibiting attractive prospects for high-end blue-sky–hued decoration for ceramics.