Reaction mechanisms of Pb(Fe2/3W1/3)O3 powders prepared by semichemical method

The mechanisms of Pb(Fe2/3W1/3)O-3(PFW) powders with pure perovskite phase prepared by semichemical method was proposed. The precursors were prepared by adding an aqueous Fe(NO3)(3) solution rather than Fe2O3 to the alcoholic slurry of PbO and WO3. The TG-DTG-DTA and XRD analysis showed that the mechanism in this method was different from those of the known columbite precursor method or conventional mixed oxide method. Fe (NO3)(3) reacted with PbO to form a intermediate of Pb-2(NO3)(2)(OH)(2) and Fe(OH)(3) and/or Fe2O3 at milling and calcinations process. The activated PbO and Pb3O4 by the intermediate reacted with WO3 to form PbWO4, which reacted directly with nascent-state Fe2O3 to transform into a pyrochlore structure of Pb2FeWO6.5 at low calcining temperature. And then the pyrochlore phase progressively reacted with Fe2O3 to form perovskite PFW phase. Additionally, the effects of excess Fe2O3 on the formation of the perovskite PFW phase have been discussed.