Balaji Birajdar

Thickness-dependent cation order and disorder in PbSc0.5Ta0.5O3 thin films grown by pulsed laser deposition

We report on thickness-dependent cation ordering and ferroelectric properties of (001)-oriented epitaxial PbSc0.5Ta0.5O3 (PST) thin films grown by pulsed laser deposition on SrTiO3 (001) and Si (001) substrates. The PST film thickness was varied from 30 to 200 nm. Only films thicker than 40 nm reveal (partial) cation ordering, which increases with thickness as confirmed by the appearance and intensity of superstructure reflections in x-ray diffraction and transmission electron microscopy. In accordance with the two-state thermodynamic model, temperature-dependent dielectric constant investigations showed the presence of two kinds of phase transitions belonging to the normal ferroelectric and the relaxor state, respectively, both being present in the PST films. The influence of cation ordering on the phase transition and ferroelectric properties is discussed in detail.

Synthesis, characterization and photocatalytic activity of mesoporous Na-doped TiO2 nano-powder prepared via a solvent-controlled non-aqueous sol–gel route

A series of mesoporous Na doped TiO2 nano-powders have been successfully prepared via a solvent-controlled non-aqueous sol–gel route. XRD, TEM and XPS results confirm the substitutional doping of Na at Ti sites and reduction in crystallite size. The increase in surface area and pore volume with Na doping is confirmed by N2 adsorption–desorption measurements. The synthesized Na doped TiO2 nano-powder revealed a superior photo-catalytic activity as compared to the synthesized TiO2 nano-powder and commercially available P25 TiO2. This could be attributed to the combined effect of reduced electron–hole recombination rate, increased surface area and enhanced crystallinity.

Synthesis, microstructure and dielectric properties of zirconium doped barium titanate

We report on synthesis, microstructural and relaxor ferroelectric properties of Zirconium(Zr) doped Barium Titanate (BT) samples with general formula Ba(Ti1-xZrx)O3 (x=0.20, 0.35). These lead-free ceramics were prepared by solid state reaction route. The phase transition behavior and temperature dependent dielectric properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature confirms phase purity of the samples. SEM observations revealed retarded grain growth with increasing Zr mole fraction. Dielectric properties of BZT ceramics is influenced significantly by small addition of Zr mole fraction. With increasing Zr mole fraction, dielectric constant decreases while FWHM and frequency dispersion increases. Polarization vs electric field hysteresis measurements reveal ferroelectric relaxor phase at room temperature. The advantages of such substitution maneuvering towards optimizing ferroelectric properties of BaTiO3 are discussed.

Ferroelectric, magnetic and optical properties of Ba and Sc co-doped KNbO3

We synthesize Ba/Sc co-doped KNbO3 ceramics with various doping concentration using the solid state route. Effect of doping on phase change, ferroelectric, magnetic and optical properties have been investigated. A gradual change of phase from orthorhombic to cubic with the increase in doping percentage was observed. Ferroelectric property characterization revealed the effect of dopants on grain growth. Magnetic response show diamagnetism in all the prepared samples. The optical properties of doped samples are found to be greatly influenced by the symmetry breaking in B-O bonds and disorder in [AO12] clusters due to the dopants.We synthesize Ba/Sc co-doped KNbO3 ceramics with various doping concentration using the solid state route. Effect of doping on phase change, ferroelectric, magnetic and optical properties have been investigated. A gradual change of phase from orthorhombic to cubic with the increase in doping percentage was observed. Ferroelectric property characterization revealed the effect of dopants on grain growth. Magnetic response show diamagnetism in all the prepared samples. The optical properties of doped samples are found to be greatly influenced by the symmetry breaking in B-O bonds and disorder in [AO12] clusters due to the dopants.

Evolution of relaxor properties in lanthanum (La) doped barium zirconate titanate

ABSTRACT La doped BZT ceramics were synthesized by solid state reaction route. XRD and SEM indicated predominantly single phase microstructure. Raman spectroscopy supported La doping at A-site. Dielectric properties revealed a diffuse phase transition in Ba(Ti0.8Zr0.2)O3. La doping of 1 atomic % enhanced the FWHM to 200 K at a frequency of 1 kHz. Further increase in La doping introduced relaxor properties but FWHM was reduced. Relaxor properties were evaluated by modified Curie-Weiss law. The degree of relaxation increased from 1.31 to 2.07 as the La doping was increased from 0 to 3 atomic %, thereby yielding a complete relaxor phase.