Green and blue materials for the ceramic industry from pink MgCoxNi1-xSiO4 (0 ≤ x ≤ 1) solid solutions

In this study, MgCoxNi1-xSiO4 (0.0 < x < 1.0) solid solutions with an olivine structure were synthetized via the chemical coprecipitation method and materials with a smaller M(II) (M = Co, Ni) amount than Co2SiO4 and Ni2SiO4 compounds were obtained. At 1200 degrees C, the Co(II) and Ni(II) were randomly distributed in the MgCoxNi1-xSiO4 (0.0 < x < 1.0) solid solutions with the olivine structure, but the occupation of Co(II) and Ni(II) ions in M1 (4a) octahedral sites was obtained at a higher level than in M2 (4c) octahedral sites. The Mg(II) ions prefer the M2 sites. This preference explains the main contribution of the M1 sites in spectra of octahedral Co(II) ions and the M1-O and M2-O distances jointly explain the pink colour of the MgCoxNi1-xSiO4 (0.0 < x < 1.0) solid so-lutions, while the colour of Co2SiO4 is blue. Spectra can be interpreted as the sum of Ni(II) and Co(II) ions in octahedral sites. When these solid solutions are enamelled, the pink colouring changes to green or blue because of the presence of tetrahedral Co(II).