Synthesis and characterization of (Mg1−xCox)4Ta2O9 with a vibrant purple color

Abstract

To develop vibrant purple inorganic pigments, (Mg_1−xCo_x)₄Ta₂O₉ (0 ≤ x ≤ 0.30) samples were synthesized using a citrate sol–gel method. The obtained powders were characterized using X-ray powder diffraction, ultraviolet and visible (UV-vis) diffuse reflectance spectroscopy, and colorimetry. The (Mg_1−xCo_x)₄Ta₂O₉ (0 ≤ x ≤ 0.30) pigments were obtained in a single phase to form solid solutions. Rietveld analysis revealed that the Co²⁺ ions were introduced into both octahedral Mg(1) and Mg(2) sites of the host lattice. In the Co²⁺-doped samples, optical absorption was observed at approximately 550 and 750 nm based on the d–d transition of octahedrally coordinated Co²⁺ ions, resulting in a purple color. The (Mg_0.75Co_0.25)₄Ta₂O₉ sample exhibited the most vibrant purple color with excellent thermal and chemical stability.