Abstract: A series of chromium-iron spinel black matte glazes were prepared at 1 200 ℃ by adjusting the ratio of chromium to iron in chromium-iron spinel. The influences of black pigments prepared under different iron-chromium ratios on the coloration of matte glazes and the coloration mechanism were studied. The results show that when the pigment formula is m(Fe₃O₄)∶m(Cr₂O₃)=80∶20 (mass ratio), the glaze is the darkest, and its L^*, a^* and b^* values are 15.90, -0.75 and 0.94, respectively. The n(Fe³⁺)∶n(Fe²⁺)=60.38∶39.62 (molar ratio) in the glaze, the content of Fe²⁺ is the highest, which is conducive to the appearance of black. The glaze is black because of the superposition of the optical effects of Fe³⁺, Fe²⁺ and Cr³⁺ under visible light. The four-coordinated Fe³⁺ is brownish red, the six-coordinated Cr³⁺ is green, and the six-coordinated Fe²⁺ is green. The superposition of the three colors can absorb all the wavelengths of visible light and make the glaze appear black. The main crystal phase in the black matte glaze is wollastonite phase. Wollastonite grains are randomly distributed in the glaze, and the grain size is within 10 μm, which produces a matting effect and makes the glaze produce a soft matte texture.

Key words: chromium-iron spinel, black glaze, matte, iron chromium ratio, wollastonite