Sequential combination of constituent oxides in the synthesis of Pb(Fe 1/2Nb 1/2)O 3 by mechanical activation

Abstract

Pb(Fe 1/2Nb 1/2)O 3 (PFN) has been successfully synthesized via a novel mechanical activation of mixed oxides and columbite precursor consisting of lead oxide and FeNbO 4. A nanocrystalline perovskite phase 5-15 nm in crystallite size was formed after 30 h of mechanical activation at room temperature for both types of starting materials. However, the nanocrystalline PFN phase derived from the mixed oxides of PbO, Fe 2O 3, and Nb 2O 5 is unstable, and develops pyroehlore phases when calcined at 500°-900°C, while no pyrochlore phase is observed for the material derived from the columbite precursor consisting of PbO and FeNbO 5. Different sintering behavior and dielectric properties were also observed between the two types of PFN. These differences are accounted for by the compositional inhomogeneity in the material derived from the mixed oxides, as was revealed by Raman spectroscopic studies. This suggests that mechanical activation is analogous to thermal activation, where the phase development is strongly dependent on the sequence of combining the constituent oxides.