V ⁵⁺ -Induced Crystal Field Modulation in Mn ⁵⁺ -Rich Ba ₃ Mn ₂ O ₈ for High-Purity Green Pigments

Ba 3 Mn 2(1– x ) V 2 x O 8 (0 ≤ x 5 ≤ 0.25) pigments were synthesized by a conventional solid-state reaction method. This study shows that diluting Mn 5+ in the Mn-rich host Ba 3 Mn 2 O 8 with V 5+ provides a high-purity green hue. All samples were obtained in a single phase with the rhombohedral Ba 3 Mn 2 O 8 structure (space group of R 3̅ m ). Optical absorption bands of the samples were observed around 378 and 689 nm due to d–d transitions of Mn 5+ . Ba 3 Mn 1.6 V 0.4 O 8 showed the pure green hue with a greenness value (− a *) of −31.1 and a hue angle ( h °) of 179.9. The values are higher than those of the commercially available Cr 2 O 3 pigments ( a * = −16.73, h ° = 140.6). XANES analysis confirmed the persistence of Mn 5+, suggesting that the enhanced color purity was caused by crystal field modulation rather than a valence change. The decrease in the average Mn–O bond length determined from the Rietveld refinement and EXAFS analysis caused a blue shift of the absorption bands, resulting in a color evolution from yellowish-green to a vivid, high-purity green. Furthermore, the optimized pigment showed excellent thermal stability, humidity, and chemical stability, indicating its significant potential for practical use as a next-generation green pigment.