2022 Volume 95 Issue 5 Pages 122-127
The effect of the microstructure on the color tone of the heat-treated red paint for ceramics, which is obtained by mixing hematite with multicomponent alkali borosilicate lead-free frit, was investigated. On the basis of X-ray diffractometry, microscopy, energy-dispersive X-ray spectroscopy, and Mössbauer spectroscopy, the color changed depending on the firing temperature, and at the same time, a part of hematite dissolved as tetrahedrally-coordinated Fe3+ in the glass matrix and the particle size of hematite increased via Ostwald ripening. The sample surface smoothening and the decrease in the number of hematite particles due to the dissolution of hematite should improve the particle dispersibility, leading to the chroma improvement in the low temperature region, whereas the hematite particle growth and excessive dissolution of hematite should decrease the chroma in the high temperature region. The coloration mechanism changed from light absorption of hematite particles to light absorption of tetrahedrally-coordinated Fe3+ in the glass matrix in the high temperature region where hematite is completely dissolved and ionized.
