Effect of annealing temperature on structural properties of the co-precipitated delafossite AgFeO2

Silver ferrite AgFeO2 delafossite powders were synthesized by the co-precipitation method with subsequent thermal treatment. The influence of annealing temperature on structural and electro-kinetic properties was intensively investigated. X-ray diffraction, Fourier-transform infrared spectroscopy, and Mossbauer spectroscopy were used as complementary methods for structural investigations. To obtain information about AgFeO2 thermal decomposition temperature thermo-gravimetric study was conducted. Moreover, the specific surface area and electro-kinetic properties were studied. Investigations revealed that co-precipitated material is a mixture of two polytypes (i.e., rhombohedral 3R and hexagonal 2H) and contains a large amount of residual water. Post-synthesis thermal treatment allowed us to establish that the optimal temperature of annealing is 573 K and the silver ferrite started to decompose at 773 K. Under the applied conditions, AgFeO2 nanoparticles with the relatively high value of the specific surface area -25 m(2) g(-1) were obtained. sigma-potential measurements disclosed iso-electric point at pH 8.5 without regard to the temperature of annealing.