Reproduction of Jun-red glazes with nano-sized copper oxide

Nano sized copper oxide was firstly employed for producing Jun-red glazes. A series of Jun-red glazes were prepared by adjusting the copper oxide nanoparticle content and the valance state of elemental copper in the glaze matrix. The coloring and microstructure of each glaze was investigated by spectrophotometer, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectrometer, and transmission electron microscope. Under reducing conditions, the red glaze color gradually darkens with increasing CuO content from 0.5 to 1.0 wt%. Interestingly, the coloring of the samples fired under reducing atmosphere turned to be green-blue, when the content of nanosized CuO was increased to 1.5 wt%. We also found that increased CuO content increases the size of phase separation in the glazes. As comparison, the coloring of samples fired without nanosized CuO are slightly blue under reducing atmosphere, which is attributed to the structural color generated owing to the Rayleigh scattering. Red color of the Jun glazes may arise from elemental copper nanoparticles. The current research utilizing modern nanotechnology provides a new insight into both the furnace transmutation and color regulating of the ancient Jun-red glazes.