Copper red glazes have received considerable attention due to their perfect
decorative effects and vivid coloration. This paper selected four different
formula copper red glazes with different colors of bright red, violet blue, dark
red, and gray blue as the samples. Based on the analysis of the colorimeter,
X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning
electron microscope (SEM), a possible coloration mechanism was proposed to
explain the variation of glaze colors. The results indicated that the glaze
layers were mainly composed of amorphous phases with few quartz diffraction
peaks and mainly presented a granulous structure and phase separation.
Increasing the content of CaO could cause color changes of the glaze due to the
high ionic potential of calcium ions, which could form a unique feature in the
glaze melt. In addition, a small amount of calcium phosphate could greatly
change the color of the glaze. The phase separation structure of the blue
samples was more obvious than that of the red samples, with a phase separation
size of less than 100 nm. The formation of droplet phase separation structure in
the glaze could lead to Rayleigh scattering and Mie scattering, which made the
color of copper red glazes blue and opacified. Increasing the content of
Cu0 and decreasing Cu+ could weaken the structural
color, which contributes to a* value of the glaze changing from 26.93 to 22.93.
At the same content of Cu0, the higher the ratio of Cu+
/Cu2+ is, the less a* value of the glaze is. Finally, the
existence of CuSiO3 in the glaze could also make the blue color.