Synthesis and Color Evaluation of Ta(5+)-Doped Bi(2)O(3)

[Image: see text] Ta(5+)-doped Bi(2)O(3) solid solutions, (Bi(1–x)Ta(x))(2)O(3+2x) (0 ≤ x ≤ 0.20), were synthesized by a conventional solid-state reaction method. The crystal structure, optical properties, and color of the pigments were characterized. The (Bi(1–x)Ta(x))(2)O(3+2x) (x = 0, 0.03, 0.04, 0.20) samples were obtained in a single-phase form, and the crystal structure depended on the Ta content; they were monoclinic α-phase (x = 0), tetragonal β-phase (x = 0.03, 0.04), and cubic δ-phase (x = 0.20). Among them, (Bi(0.97)Ta(0.03))(2)O(3.06) strongly absorbed visible light at the wavelength shorter than 480 nm and exhibited the most vivid orange color. The redness value (a*) was comparable to that of commercial orange pigments, and the yellowness value (b*) was slightly larger. Although it is necessary to improve chemical stability, the (Bi(0.97)Ta(0.03))(2)O(3.06) pigment has potential for an environmentally friendly inorganic orange pigment.