Influence of raw materials in crystallization of Na2MSiO4 or M2SiO4 (M = Mg, Co) solid solutions from Na2Mg1-xCoxSiO4 (0.0 ≤ x ≤ 1.0) compositions

In this study, Na₂Mg_1-xCo_xSiO₄ (0.0 ≤ x ≤ 1.0) compositions were prepared. The structural characterization indicates the formation of solid solutions with the Na₂MSiO₄ (M = Mg, Co) orthorhombic structures from Na₂CO₃. The decomposition of Na₂CO₃ generates NaSiO₃ and at 1000 °C the Na₂MSiO₄ (M = Mg, Co) structures are obtained. From coprecipitation of aqueous suspensions using raw materials with chlorides, crystallizes NaCl which inhibits the formation of Na₂MSiO₄ (M = Mg, Co) structures and olivine structure is obtained at 1000 °C. In these compositions, the amount of cobalt is reduced with respect to Co₂SiO₄ and MgCoSiO₄ olivines. Coloration of these materials is intense Blue in materials prepared without chlorides or Blue-Violet in samples prepared with chlorides at 1000 °C (0.2 < x ≤ 0.8). Colour of these materials is due to tetrahedral or octahedral Co(II) in Na₂MSiO₄ (M = Mg, Co) or M₂SiO₄ (M = Mg, Co). These fired phases were 2 % weight enamelled with a commercial glaze and the obtained blue materials are in accordance with the dissolution in glazes of the solid solutions containing only tetrahedral Co(II) ions.