Dibyaranjan Rout

Enhanced multiferroic properties of single-phase BiFeO3 bulk ceramics by Ho doping

Dense single-phase BiFeO3 and Bi0.9Ho0.1FeO3 ceramics were prepared by the solid-state reaction method. With Ho doping, the remnant polarization of BiFeO3 was enhanced and the switching characteristics improved at low electric fields. Ho doping increased the breakdown voltage with a reduction of the leakage current while mitigating the remnant polarization at high electric fields. These results can explain conflicting findings regarding the effects of rare-earth doping on remnant polarization. Bi0.9Ho0.1FeO3 exhibited peculiar double hysteresis looplike magnetization-magnetic field curves with a much enhanced remnant magnetization. These improved properties obtained by Ho doping demonstrate the possibility of enhancing the multiferroic applicability of BiFeO3.

Dielectric and Raman scattering studies of phase transitions in the (100−x)Na0.5Bi0.5TiO3–xSrTiO3 system

Temperature-driven and composition-driven phase transformations in a mixed A-site Pb-free solid solution series of (100−x)Na0.5Bi0.5TiO3–xSrTiO3 (0≤x≤40) were investigated by means of x-ray diffraction, dielectric, and Raman scattering techniques over a temperature range of 20–550 °C. The phonon anomalies observed in the room temperature Raman spectra with increasing Sr concentration revealed a morphotropic phase boundary (MPB) at x∼20. The distinct and discontinuous changes in dielectric properties at x∼20 confirmed the existence of MPB. On heating, the Raman spectral features for different compositions displayed substantial changes at temperatures almost identical to the critical temperatures determined by dielectric measurement, such as ferroelectric–antiferroelectric (Td), rhombohedral–tetragonal (TR-T), and antiferroelectric–paraelectric (Tm) phase transition temperature. However, the two phonon anomalies observed at higher temperatures (∼400 and 500 °C for x=10) suggested the coexistence of rhombohe...

Low temperature hydrothermal epitaxy and Raman study of heteroepitaxial BiFeO3 film

By hydrothermal epitaxy, a heteroepitaxial BiFeO3 (BFO) film of ∼2.5 μm thickness was grown on a (100)-oriented single-crystalline SrTiO3 (STO) substrate at 200 °C, which is at least 250 °C lower than the conventional techniques used thus far. The x-ray diffraction pattern indicated the formation of a single-phase perovskite structure that was highly oriented along the (00l) lattice plane. Pole-figure and Φ-scan results confirmed the cube-on-cube epitaxial relationship of BFO∥STO. The Raman active vibrational modes showed anomalous changes in the vicinity of the Neel temperature (TN), which was attributed to spin-phonon coupling.