Coloring properties of blue inorganic pigments based on cobalt/nickel doped strontium magnesium β-alumina structure in 3YSZ ceramics

Abstract

Blue inorganic pigments based on cobalt or nickel doped strontium magnesium β-alumina structure (β-SAM) solid solutions were successfully fabricated using the solid state method for the first time. Compared with commercial cobalt blue (CoAl2O4, 33.32 wt% Co, −b∗ = 18.5), Sr0.857Mg0.714Al9.986Co0.3O17-δ with significantly lower Co content (2.71 wt%) achieved a more vibrant blue color (−b∗ = 57.5). The ocean blue color of Sr0.857Mg0.714Al10.286-xCoxO17-δ (0.05 ≤ x ≤ 0.3) originates from the A24(F4)→T14(P4) transition of the tetrahedral Co2+, while the sky blue color of Sr0.857Mg0.714Al10.286-xNixO17-δ (0.05 ≤ x ≤ 0.3) is due to the T13(F3)→T13(P3) transition in tetrahedral Ni2+. Chemical stability tests demonstrated good acid and alkali resistance of as-prepared pigments. Additionally, blue 3YSZ ceramic composites incorporating 5–10 wt% Sr0.857Mg0.714Al9.986Co0.3O17-δ or Sr0.857Mg0.714Al9.986Ni0.3O17-δ pigments as chromophores were obtained after high temperature sintering. Ocean blue ceramics composed of 10 wt% Sr0.857Mg0.714Al9.986Co0.3O17-δ and 90 wt% 3YSZ with 0.27 wt% Co exhibited a larger −b∗ value (−b∗ = 43.3) compared to 10 wt% CoAl2O4-3YSZ blue ceramic composite (−b∗ = 34.0, 3.33 wt% Co). FE-SEM analysis showed that the pigment phase remained stable after high temperature sintering with 3YSZ, with clear grain boundaries observed. The mechanical properties of the fabricated blue ceramics were comparable to those of pure 3YSZ ceramic, which highlights the potential of Co/Ni doped Sr0.857Mg0.714Al10.286O17 pigments in ceramic applications.