Addition of rare earth cation on formation and properties of various cobalt phosphates

Various cobalt phosphate pigments were prepared with the addition of rare earth cation by heating the mixtures of ammonium dihydrogenphosphate, cobalt carbonate, and rare earth (Y, La, and Nd) oxide. The thermal behavior of these mixtures was characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), and FT–IR analyses. The thermal products were estimated from scanning electron micrographs (SEM), particle size distribution, specific surface area, UV–vis reflectance spectra, and fluorescence spectra. Furthermore, the acid and base resistance of these materials was evaluated. The thermal reactions were clarified in these systems. Formation of cobalt–neodymium phosphate composite particles were considered from specific surface area. Cobalt pyrophosphate and cyclo-tetraphosphate had more vivid color hue than cobalt orthophosphate. These condensed phosphates had better acid and base resistance. By the addition of rare earth elements, the acidic and basic resistance of cobalt phosphates was remarkably improved.