Development of blue ceramic dyes from cobalt phosphates

In this study the development of blue ceramic dyes from compositions based on phosphate structures have been investigated. The replacement of cobalt by copper or iron to minimize the Co content have been considered. MFeO(PO4) (M = Co, Cu) solid solutions have been obtained with Co1−xCuxFeOPO4 (0 ≤ x ≤ 1) compositions prepared from gels and fired at 1000 °C/2 h. Co1−xCuxFeOPO4 compositions are not indicated to minimize the Co content in ceramic dyes because they decompose in glazed samples and pinhole defect is obtained. From FeCoOPO4–2FePO4 compositions, Co3Fe4(PO4)6 structure introduces the Co2+ ions into glassy matrix and suitable blue materials are obtained. In the conditions of this study, optimal cobalt amount is about 10 wt% Co from Co1−xFe1+xO1−x(PO4)1+x (x ≈ 0.6) compositions.