Structural, ⁵⁷Fe Mössbauer and XPS studies of mechanosynthesized nanocrystalline Nd_0.33Eu_0.67Fe_1-xCr_xO₃ particles

We report on the structure and surface composition of Nd_0.33Eu_0.67Fe_1-xCr_xO₃ (x = 0.0, 0.3, 0.5, 0.7, 0.9 and 1.0) nanoparticles (∼30 nm) mechanosynthesized at temperatures that are ∼ 470–700 °C lower than those at which the pure and doped pristine materials conventionally form. XRD Rietveld and FT-IR analyses show that with increasing x the lattice parameters decrease and the bond lengths and angles vary in a way that reduces crystalline distortion. Whilst the majority of the Eu³⁺/Nd³⁺ and Fe³⁺/Cr³⁺ cations occupy their normal perovskite-related A- and B-sites, respectively, ∼ 5 % of them exchange sites. ⁵⁷Fe Mössbauer spectroscopy favours the presence of these antisites and reveals a superparamagnetic behaviour at 298 K that enhances with increasing x. XPS measurement reveals a complex surface composition of the nanoparticles with traces of Eu₂O₃, Nd₂O₃, Cr₂O₃ and Fe₂O₃ as well as partial O²⁻-deficiency.