The effects of aluminium (Al3+)-dopant on the precipitation of uniform lath-like alpha-FeOOH particles, the obtention and growth of alpha-(Fe,Al)OOH and alpha-(Fe,Al)(2)O-3 solid solutions, particle size and shape were investigated using X-ray powder diffraction, Mossbauer and Fourier transform infrared spectroscopies, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Acicular alpha-FeOOH particles, precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH), were used as reference material. The influence of Al-dopant was investigated by adding varying amounts of Al3+ ions to the initial FeCl3 solution. In the presence of lower concentrations of aluminium ions (up to 11.11 mol%) alpha-(Fe,Al)OOH as a single phase was formed, whereas higher concentrations led to an additional obtention and growth of alpha-(Fe,Al)(2)O-3. Al-for-Fe substitution in the alpha-FeOOH and alpha-Fe2O3 structures was confirmed by a decrease in the unit-cell dimensions, a decrease in the hyperfine magnetic field and an increase in the wave number of the infrared absorption bands. The presence of lower concentrations of aluminium ions (up to 11.11 mol%) in the precipitation system did not affect the size and shape of the alpha-(Fe,Al)OOH particles, whereas higher concentrations influenced a decrease in the length and aspect ratio. In the presence of 42.86 mol% Al3+ ions fairly uniform disc-shaped alpha-(Fe,Al)(2)O-3 were formed. (C) 2010 Elsevier B.V. All rights reserved.