Microstructure engineering to improve the multiferroic behavior in Ti, RE co-doped BiFeO3 ceramics (RE = Sm or Nd)

The obtaining of single-phase BiFeO3 based multiferroic materials with an effective functional response and a low leakage current still represents a major challenge. One of the most commonly resorted strategies for improving... [ view full abstract ]

The obtaining of single-phase BiFeO₃ based multiferroic materials with an effective functional response and a low leakage current still represents a major challenge. One of the most commonly resorted strategies for improving these physical properties relies on the incorporation of Sm³⁺ or Nd³⁺ cations into the BiFeO₃ crystal lattice, where the rare earth cations replace the Bi³⁺ at the A positions of the perovskite structure. Through this procedure, a structural phase transition is produced from the rhomboedrical (undoped) phase to an orthorrombic (doped) phase that may lead to an enhancement of the material´s multiferroic behaviour. However, a high conductivity still persists in the bulk samples, which hinders their polarization. This can be solved by introducing the RE³⁺ cations simultaneously with Ti⁴⁺. Titanium ions exhibit a low solubility in the BiFeO₃ lattice and generate a complex micro- nanostructure comprised by grains of around 50 nm in size which are separated by Ti-rich grain boundaries. This particular microstructure combined with the structural modification introduced by the RE doping, eventually results in both a significant reduction of the electrical conductivity and a substantial enhancement of the functional response of the co-doped ceramics.