The influence of Cd-dopant on the properties of α-FeOOH and α-Fe2O3 particles precipitated in highly alkaline media

The effects of Cd-dopant on the phenomenology of the precipitation of α-(Fe, Cd)OOH and α-(Fe, Cd)2O3 particles, the formation of solid solutions, particle size and their geometrical shapes were investigated using Mössbauer and Fourier transform infrared (FT-IR) spectroscopies, field emission scanning electron microscopy (FE SEM) and energy dispersive X-ray analysis (EDS). The formation of merely α-(Fe, Cd)OOH solid solutions was measured up to r = 0.0196, where r = [Cd]/([Cd] + [Fe]). The formation of two types of solid solutions, α-(Fe, Cd)OOH and α-(Fe, Cd)2O3 was found at r between 0.0291 and 0.0698, whereas the formation of an α-(Fe, Cd)2O3 solid solution alone was obtained at r = 0.0909. The incorporation of Cd-substitutions into α-FeOOH and α-Fe2O3 structures decreased the 〈Bhf〉 values of the corresponding hyperfine magnetic field. The IR band at 639 cm−1, recorded for α-FeOOH, was found to be sensitive to Cd-substitutions. With an increased r value a gradual elongation of α-(Fe, Cd)OOH particles along the c-axis was observed, with the maximum elongation (∼600-700 nm) obtained at r = 0.0476. At the same time, particle width (b-axis direction) and thickness (a-axis direction) showed a gradual decrease. With a further increase in the r value the length of α-(Fe, Cd)OOH particles rapidly decreased. α-(Fe, Cd)2O3 particles ∼100-200 nm in size were obtained at r = 0.0909.