Mechanosynthesis of the Whole Y(1−x)Bi(x)Mn(1−x)Fe(x)O(3) Perovskite System: Structural Characterization and Study of Phase Transitions

Perovskite BiFeO(3) and YMnO(3) are both multiferroic materials with distinctive magnetoelectric coupling phenomena. Owing to this, the Y(1−x)Bi(x) Mn(1−x)Fe(x)O(3) solid solution seems to be a promising system, though poorly studied. This is due to the metastable nature of the orthorhombic perovskite phase of YMnO(3) at ambient pressure, and to the complexity of obtaining pure rhombohedral phases for BiFeO(3)-rich compositions. In this work, nanocrystalline powders across the whole perovskite system were prepared for the first time by mechanosynthesis in a high-energy planetary mill, avoiding high pressure and temperature routes. Thermal decomposition temperatures were determined, and structural characterization was carried out by X-ray powder diffraction and Raman spectroscopy on thermally treated samples of enhanced crystallinity. Two polymorphic phases with orthorhombic Pnma and rhombohedral R3c h symmetries, and their coexistence over a wide compositional range were found. A gradual evolution of the lattice parameters with the composition was revealed for both phases, which suggests the existence of two continuous solid solutions. Following bibliographic data for BiFeO(3), first order ferroic phase transitions were located by differential thermal analysis in compositions with x ≥ 0.9. Furthermore, an orthorhombic-rhombohedral structural evolution across the ferroelectric transition was characterized with temperature-dependent X-ray diffraction.