Sumit Bhardwaj

Room temperature multiferroic properties and magnetoelectric coupling in Sm and Ni substituted Bi4−xSmxTi3−xNixO12±δ (x = 0, 0.02, 0.05, 0.07) ceramics

Lead free multiferroic Bi4−xSmxTi3−xNixO12±δ (x = 0.02, 0.05, and 0.07) samples have been synthesized by conventional solid state route. X-ray diffraction analysis reveals single phase up to x = 0.07, and a secondary phase appears at x > 0.07. Raman spectroscopy confirms the local distortions in the crystal. Field emission scanning electron microscopy shows plate like grains. Substitution has increased the orthorhombic distortion, grain size, and hence the ferroelectric transition temperature (Tc). A significant reduction in the values of dielectric constant (e′) and loss tangent (tan δ) has been observed with the increase of Sm and Ni ions. The increase in dc resistivity at room temperature has been found with substitution. Enhancement in the values of remnant polarization (2Pr) and magnetization (2Mr) is observed. Magnetoelectric coupling coefficient (α) values of 0.60 mV/cm/Oe are achieved in Bi4−xSmxTi3−xNixO12±δ ceramic samples. Hence, we have successfully converted the ferroelectric Bi4Ti3O12 into a...

Ferroelectric Bi3.3La0.7Ti3O12-poly (vinylidene-fluoride) composites with enhanced dielectric properties

Ferroelectric ceramic polymer composites of Poly (vinylidene-fluoride) and Bi3.3La0.7Ti3O12 (BLT) were prepared by simple solution casting method. The structural, dielectric and morphological properties were studied systemically. The dielectric results showed that the composites have high dielectric constant with very low dielectric loss. At room temperature, a 10 wt% loaded BLT/PVDF composite film showed a dielectric constant of 109.48, which is six times greater in comparison to pure PVDF. Morphological studies reveal the formation of spherulattic structure of PVDF. These lead free composites with enhanced dielectric properties may prove tremendous potential for energy storage devices.

Effect of Bi4Ti3O12 nanoparticles on the electroactive phase content of poly (vinylidene-difluoride) composite films

Poly (vinylidene-difluoride) (PVDF) composite films with homogeneously dispersed Bi4Ti3O12 nanoparticles were synthesized by spin coating method from mixed solvent solutions. The effects of ferroelectric nanoparticles loading on the formation of α, β and γ phases of PVDF were studied using X-ray diffraction, infrared and Raman spectroscopy. The amount of the ferroelectric β and γ phases present in the composite films was found to increase with increased nanoparticles loading. We have shown that the formation of electroactive phases of PVDF with extended chain conformations can be enhanced by the addition of a well-dispersed nanoparticles loading.

Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications.

Raman spectroscopy studies of Bi4Ti3O12nanocrystals prepared by mechanical alloying

Grain size plays a very important role to study the properties of ferroelectric materials. We synthesized the Bi 4 Ti 3 O 12 (BIT) nanocrystals by mechanical alloying, by milling the powder for different milling time. X-ray diffraction studies confirmed the formation of single phase nanocrystals and crystallite size found to decreases with increase in milling time. Raman spectroscopy studies reveal that with the decrease in grain size intensity of Raman active modes decreases and diminishes as we move from crystallite size of 26 nm to 11 nm. Increase in surface energy at nano level and induced strains due to large number of surface atomic layers may be the reason for this phenomenon and can be used to study the grain size effect.

Raman spectroscopy studies of Bi[sub 4]Ti[sub 3]O[sub 12] nanocrystals prepared by mechanical alloying

Grain size plays a very important role to study the properties of ferroelectric materials. We synthesized the Bi 4 Ti 3 O 12 (BIT) nanocrystals by mechanical alloying, by milling the powder for different milling time. X-ray diffraction studies confirmed the formation of single phase nanocrystals and crystallite size found to decreases with increase in milling time. Raman spectroscopy studies reveal that with the decrease in grain size intensity of Raman active modes decreases and diminishes as we move from crystallite size of 26 nm to 11 nm. Increase in surface energy at nano level and induced strains due to large number of surface atomic layers may be the reason for this phenomenon and can be used to study the grain size effect.

Dielectric study and multiferroic behaviour of Fe and Sm doped bismuth titanate

Bi4-xSmxTi3-xFexO12(x = 0,0.1,0.2,0.3) ceramic samples were prepared by solid state reaction method. All the samples were investigated by X-ray diffraction, Impedance Analyzer and Vibrating Sample Magnetometer techniques. X-ray diffraction (XRD) of all samples exhibit single phase of Aurivillius type structure. Dielectric studies reveals non –relaxor behaviour of all the samples. There is dispersion in the Dielectric constant, but ferroelectric transition temperature (Tc) does not show any dispersion. With increase in composition of Sm and Fe in the BIT the transition temperature of the samples increases. From the phase transitions, it is shown that all the samples have ferroelectric behaviour. Samples so prepared also show ferromagnetic behaviour. On increasing the Fe content the remnant magnetization of the samples increases, so doped BIT shows multiferroic behaviour.

Raman spectroscopy studies of Bi4Ti3O12 nanocrystals prepared by mechanical alloying

Grain size plays a very important role to study the properties of ferroelectric materials. We synthesized the Bi 4 Ti 3 O 12 (BIT) nanocrystals by mechanical alloying, by milling the powder for different milling time. X-ray diffraction studies confirmed the formation of single phase nanocrystals and crystallite size found to decreases with increase in milling time. Raman spectroscopy studies reveal that with the decrease in grain size intensity of Raman active modes decreases and diminishes as we move from crystallite size of 26 nm to 11 nm. Increase in surface energy at nano level and induced strains due to large number of surface atomic layers may be the reason for this phenomenon and can be used to study the grain size effect.