Unveiling the science behind the tea bowls from the Jizhou kiln. Part II. Microstructures and the coloring mechanism

In this part of the study, optical microscope, field emission scanning electron microscope-energy dispersive spectrometer, transmission electron microscope-selected area diffraction-energy dispersive spectrometer, micro-Raman and reflectance spectrum were applied to further study the microstructures of the characteristic areas of the glazes and illustrate the coloring mechanism of the “hare's fur” tea bowls with blue or bluish violet patterns. The results show that due to the diffusion between the cover glaze and ground glaze caused by compositional difference, as well as the “boiling effect” of the ground glaze, local chemical composition changes to form the different microstructures in different regions. Large sized interconnected phase separation structure with approximately 350 nm characteristic size forms in the unreacted portion of the cover glaze, leading to the scattering of all wavelengths of the incident visible light. With the contribution of the ground glaze which has low immiscibility tendency, small sized interconnected phase separation structure with approximately 170 nm characteristic size forms at the edge of the white region, leading to the scattering of the blue light range of the incident visible light. The fluctuation of thermal history gives various appearance to the Jizhou “hare's fur” tea bowls, although they share the same coloring mechanism. In general, chemical composition, microstructure and firing schedule cooperate with each other to create the changeful appearance of the Jizhou tea bowls.