Balaram Sahoo

Studies of ferroelectric properties and leakage current behaviour of microwave sintered ferroelectric Na0.5Bi0.5TiO3 ceramic

ABSTRACT Single phase lead-free ferroelectric ceramic Na0.5Bi0.5TiO3 (NBT) is synthesized using sol-gel method and sintered using microwave sintering technique. The structural, microstructural, and electrical properties are investigated in detail. Rietveld refinement technique is used to analyse XRD pattern. SEM micrograph shows the densely packed micrometre sized grains. Ferroelectric hysteresis loops for unpoled and poled samples confirm its ferroelectric nature. The characteristic ferroelectric properties like remanent polarization and coercive field are found to be 84.8 µC/cm2, 71.8 µC/cm2 and 58.8 kV/cm, 58.6 kV/cm respectively for the unpoled and poled samples. The current versus voltage curve of the NBT follow the bulk-limited space-charge conduction mechanism.

Neutron diffraction, Mössbauer and electron paramagnetic resonance studies of Pb0.8Bi0.2Fe0.6Nb0.4O3 multiferroic

The Pb0.8Bi0.2Fe0.6Nb0.4O3 (PFN-BFO) multiferroic solid solution was synthesized by single step solid state reaction method with low calcination (700 °C/2h) and sintering (800 °C/3h) temperatures. Single phase formation was confirmed through X Ray Diffraction (XRD) and Neutron Diffraction (ND) at room temperature (RT). The structural analysis was carried out by Rietveld refinement through the Fullprof program. Refined XRD and ND patterns confirms the monoclinic structure with Cm space group and obtained cell parameters from the ND data are a = 5.6449(8) A, b = 5.6536(5) A, c = 4.0017(6) A and β = 89.930(4)°. ND data at RT exhibits G-type antiferromagnetic structure. The Mossbauer and Electron Paramagnetic Resonance (EPR) spectroscopy studies were carried out at RT. The isomer shift and the quadrupole splitting of the Mossbauer spectra confirm the Fe in +3 states. An EPR spectrum shows a single broad slight asymmetric line, is an evidence of Fe in +3 states. ND, Mossbauer and EPR studies are the clear evid...

Neutron Diffraction, Mössbauer Effect and Electron Paramagnetic Resonance Studies on Multiferroic Pb(Fe2/3W1/3) O3

Multiferroic Pb(Fe2/3W1/3)O-3 ceramics were synthesized via a modified two-stage Columbite method. Single phase formation was confirmed from the analysis of x-ray and neutron diffraction patterns recorded at room temperature. Structural analysis of the diffraction data reveals cubic phase (space group Pm-3m) for the title compound. Magnetic structure of the title compound at room temperature exhibits G-type antiferromagnetic structure. The Mossbauer spectroscopy and Electron Paramagnetic Resonance (EPR) studies were carried out at 300 K. The isomer shift and quadrupole splitting of the Mossbauer spectra confirms the trivalent state of iron (Fe3+). The Mossbauer spectra also suggest that the iron and tungsten are randomly distributed at the octahedral, B site. EPR spectra show a single broad line associated with Fe3+ ions. Both spectra clearly exhibit weak ferromagnetic behaviour of Pb(Fe2/3W1/3)O-3 ceramic at 300 K. Considering neutron diffraction, Mossbauer and EPR results together, it may be stated here that Pb(Fe2/3W1/3)O-3 exhibits antiferromagnetic behavior along with weak ferromagnetism at room temperature.