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

Abstract Ceramic pigments, CeO 2 ·α-Fe 2 O 3 and CeO 2 ·Pr 6 O 11 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 CeO 2 ·α-Fe 2 O 3 , and light-brown to earth-brown for the system CeO 2 ·Pr 6 O 11 , and a tendency to the red color in the reflectance spectrum was observed in all pigments. The CeO 2 ·Pr 6 O 11 system, synthesized through both methods, and the CeO 2 ·α-Fe 2 O 3 system, synthesized through modified sol–gel, presented only cerianite phase. The lattice of CeO 2 ·α-Fe 2 O 3 system presents a tendency to expand with the addition of Fe 3+ ions, through both methods of synthesis, suggesting an interstitial solid solution formation. The Fe 3+ ion solubility limit within the CeO 2 lattice is between 2 and 3% in mol. The 57 Fe Mossbauer spectroscopy analysis revealed that the sample with 2 and 3 mol% α-Fe 2 O 3 , synthesized by the solid state reaction or by the modified sol–gel method presented hematite signals, together with Fe 3+ signals within the cerium oxide lattice. For the system CeO 2 ·Pr 6 O 11 , changes in the mechanism of solid solution formation depends on the oxidation number of praseodymium reagent.