Phase transformation of titania gels highly doped with Fe in different sintering atmospheres

The effect of sintering atmosphere on the phase transformation of high contents of Fe-doped titania gels was studied. Experimental results show that the sintering atmosphere has less influence in the transformation temperature of the gel to anatase. Sintering in an oxidizing atmosphere causes precipitation of the Fe2O3 phase while sintering in a reducing atmosphere promotes the transformation of the gel to anatase, causes the Fe ions to dissolve entirely into the titania crystals, and enhances the transformation temperature of anatase to rutile. Fe-doping inhibits the transformation of the gel to anatase while promoting the transformation of anatase to rutile and decreasing the mean crystal size of the titania crystals during sintering in oxidizing or reducing atmospheres. Moreover, the action mechanism of the sintering atmosphere and Fe-doping are discussed in terms of oxygen vacancies, ionic valence and substitutions.

► Sintering atmosphere has less influence in transition temperature of gel to anatase.
► Reducing atmosphere enhances the transition temperature of anatase to rutile.
► Reducing atmosphere causes complete dissolution of Fe ions into titania crystals.
► Fe-doping facilitates the formation of rutile in both atmospheres.
► This facilitation starts from lower concentrations of Fe in reduction atmosphere.