Synthesis and characterization of CeO2·α-Fe2O3 and CeO2·Pr6O11 ceramic pigments through the solid state reaction and modified sol–gel method

• CeO2·Pr6O11 and CeO2·α-Fe2O3 based inorganic pigments were synthesized.
• Mossbauer shows the presence two sites for iron ions in the system CeO2·α-Fe2O3.
• The CeO2 lattice expanded with the interstitial solution with Fe3+ ions.
• For CeO2·Pr6O11, the mechanism of solid solution formation depends on precursor.
• The prepared pigments presented a tendency to the red color.

Ceramic pigments, CeO2·α-Fe2O3 and CeO2·Pr6O11 systems, were synthesized through the solid state reaction at 1300 °C/3 h and modified sol–gel method at 1300 °C/3 h. Pigments presented shades from brown to reddish-orange for the system CeO2·α-Fe2O3, and light-brown to earth-brown for the system CeO2·Pr6O11, and a tendency to the red color in the reflectance spectrum was observed in all pigments. The CeO2·Pr6O11 system, synthesized through both methods, and the CeO2·α-Fe2O3 system, synthesized through modified sol–gel, presented only cerianite phase. The lattice of CeO2·α-Fe2O3 system presents a tendency to expand with the addition of Fe3+ ions, through both methods of synthesis, suggesting an interstitial solid solution formation. The Fe3+ ion solubility limit within the CeO2 lattice is between 2 and 3% in mol. The 57Fe Mössbauer spectroscopy analysis revealed that the sample with 2 and 3 mol% α-Fe2O3, synthesized by the solid state reaction or by the modified sol–gel method presented hematite signals, together with Fe3+ signals within the cerium oxide lattice. For the system CeO2·Pr6O11, changes in the mechanism of solid solution formation depends on the oxidation number of praseodymium reagent.