Structural and Dielectric Progression of 5 % Gd Doped BiFeO3 Nanoparticles Through Cr (2-8%) Doping

This study reports the structural modifications in undoped multiferroic BiFeO3 (bismuth ferrite or BFO) nanoparticles caused by doping at both the A-site (by 5% Gd) and B-site (by 2-8% Cr) and the resulting improvements in dielectric characteristics. Both un-doped and doped BFO nanoparticles were synthesized using the sol-gel technique and annealed at 600°C for crystallization. X-ray diffractometry (XRD) reveals a phase transition from rhombic (R3c) to orthorhombic (Pn21a). Field Emission Scanning Electron Microscopy (FESEM) study shows the production of nanoparticles with sizes ranging from 80 to 130 nm. Impedance analyzer experiments (100 Hz-10 MHz) show that the dielectric characteristics of doubly doped BFO are very stable over a wide frequency range. The dielectric permittivity of co-doped BFO decreases with Cr doping concentration up to x = 0.06 before reversing. The conductivity drops dramatically as the Cr content rises. Journal of Engineering Science 12(3), 2021, 101-110

Observation of Spin Reorientation Transitions in Lead and Titanium-Modified BiFeO3 Multiferroics

We report the synthesis and basic characterization details of bulk Bi1 − xPbxFe1 − xTixO3 (x = 0.05 and 0.1) polycrystalline samples, which have been synthesized using the conventional solid-state route. We studied the effects of partially doping of Pb and Ti ion on structural, vibrational, and magnetic properties of multiferroic BiFeO3. X-ray diffraction (XRD) was used for crystallographic studies, followed by Rietveld refinement, and phase formation of the compounds was confirmed, which indicates that the sample has rhombohedral (R3c, 100%) symmetry for x = 0.05 and R3c (98%) + P4mm (2%) symmetry for x = 0.1. X-ray absorption spectroscopy has been probed at Fe L2,3 and O K edges to determine the valence (charge) state of Fe in BiFeO3. Interestingly, the magnetic measurement results revealed the existence of spin reorientation transition in Pb and Ti-modified BiFeO3, which indicates that the BiFeO3 samples studied may find promising applications in memory and spintronic devices.

Chemical ordering and magnetic phase transitions in multiferroic BiFeO3-AFe1/2Sb1/2O3 (A-Pb, Sr) solid solutions fabricated by a high-pressure synthesis

Ceramic samples of BiFeO3-based perovskite solid solutions with the highly ordered complex perovskites PbFe[Formula: see text]Sb[Formula: see text]O3 (PFS) and SrFe[Formula: see text]Sb[Formula: see text]O3 (SFS) were obtained using high-pressure synthesis at 4-6 GPa. Mössbauer studies revealed that BiFeO3-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO3-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature TN for BiFeO3-SFS compositions is close to the [Formula: see text] dependence for BiFeO3 solid solution with disordered perovskite PbFe[Formula: see text]Nb[Formula: see text]O3 (PFN). In contrast to this [Formula: see text] dependence for BiFeO3-PFS compositions nicely follows the theoretical [Formula: see text] dependence calculated for the case of the ordered distribution of Fe[Formula: see text] and non-magnetic Sb[Formula: see text] ions in the lattice (chemical ordering).