Yesappa Kolekar | Savitribai Phule Pune University (original) (raw)
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Papers by Yesappa Kolekar
Transactions of the Indian Ceramic Society, 2019
The structural, ferroelectric, piezoelectric and dielectric properties of lead-free 0.45Ba 0.92 C... more The structural, ferroelectric, piezoelectric and dielectric properties of lead-free 0.45Ba 0.92 Ca 0.08 TiO 3-0.55BaTi 0.96 Zr 0.04 O 3 (BCT8-BZT4) ceramics synthesized by conventional solid state reaction method have been reported. Structural analyses by X-ray diffraction (XRD) and Raman spectroscopic measurements indicate that the BCT8-BZT4 ceramics possesses both tetragonal (space group P4mm) and orthorhombic (space group Amm2) crystal structures at room temperature. Dense microstructure with 5-7 m grain size has been observed from scanning electron micrographs. Ferroelectric nature of BCT8-BZT4 has been confirmed from the polarization-electric field (P-E) hysteresis loop measurements. For BCT8-BZT4, the values of maximum polarization (P max =17.24 C/cm 2), remnant polarization (P r =6.36 C/cm 2), coercive electric field (E c =3.66 kV/cm) and direct piezoelectric coefficient (d 33~2 20 pC/N) have been observed to be comparable with those of lead based piezoelectric ceramics. The BCT8-BZT4 ceramics shows usual dielectric dispersion with dielectric constant ~1210 above 100 kHz frequency at room temperature. The observed properties show that the BCT8-BZT4 ceramics is suitable for ferroelectric memory, piezoelectric sensor, capacitor, etc applications. Thus, it has been predicted that BCT8-BZT4 may be a potential candidate for replacing lead-based piezoelectric ceramics.
Physical Chemistry Chemical Physics, 2013
Complex (multivalent/mixed valent) oxides involving two or more cations (e.g. ABO3, AB2O4 and A2B... more Complex (multivalent/mixed valent) oxides involving two or more cations (e.g. ABO3, AB2O4 and A2B2O7) exhibit the most fascinating range of physical and chemical properties amongst the family of materials systems. There is growing interest in nanoscale forms of such oxides which emanates from the novel changes in their properties with size. To obtain nanomaterials with a high degree of crystallinity it is desirable to first make crystalline oxide powders by high temperature processing and then mill them down to nanometer size. In this paper we show that simple citric acid treatment of BiFeO3 and Bi2O3 powders leads to the desired micron-scale to nanoscale transformation, yielding nearly monodispersed nanoparticles. Importantly, these are highly dispersible and stable in water. By performing similar experiments on Fe3O4 and Fe2O3 we have elucidated the possible mechanism, which hinges on valence-controlled dissolution and ripening phenomena.
Bulletin of the American …, 2011
Recently, rare-earth orthoferrites have received much attention. Their propensity for multiferroi... more Recently, rare-earth orthoferrites have received much attention. Their propensity for multiferroic capabilities could play a key role in the fabrication of an efficient spintronic system. Such materials as BiFeO3 and CeFeO3 have already shown promise for uses in microphotonics as well ...
Applied Physics Letters, 2012
Transactions of the Indian Ceramic Society, 2019
The structural, ferroelectric, piezoelectric and dielectric properties of lead-free 0.45Ba 0.92 C... more The structural, ferroelectric, piezoelectric and dielectric properties of lead-free 0.45Ba 0.92 Ca 0.08 TiO 3-0.55BaTi 0.96 Zr 0.04 O 3 (BCT8-BZT4) ceramics synthesized by conventional solid state reaction method have been reported. Structural analyses by X-ray diffraction (XRD) and Raman spectroscopic measurements indicate that the BCT8-BZT4 ceramics possesses both tetragonal (space group P4mm) and orthorhombic (space group Amm2) crystal structures at room temperature. Dense microstructure with 5-7 m grain size has been observed from scanning electron micrographs. Ferroelectric nature of BCT8-BZT4 has been confirmed from the polarization-electric field (P-E) hysteresis loop measurements. For BCT8-BZT4, the values of maximum polarization (P max =17.24 C/cm 2), remnant polarization (P r =6.36 C/cm 2), coercive electric field (E c =3.66 kV/cm) and direct piezoelectric coefficient (d 33~2 20 pC/N) have been observed to be comparable with those of lead based piezoelectric ceramics. The BCT8-BZT4 ceramics shows usual dielectric dispersion with dielectric constant ~1210 above 100 kHz frequency at room temperature. The observed properties show that the BCT8-BZT4 ceramics is suitable for ferroelectric memory, piezoelectric sensor, capacitor, etc applications. Thus, it has been predicted that BCT8-BZT4 may be a potential candidate for replacing lead-based piezoelectric ceramics.
Physical Chemistry Chemical Physics, 2013
Complex (multivalent/mixed valent) oxides involving two or more cations (e.g. ABO3, AB2O4 and A2B... more Complex (multivalent/mixed valent) oxides involving two or more cations (e.g. ABO3, AB2O4 and A2B2O7) exhibit the most fascinating range of physical and chemical properties amongst the family of materials systems. There is growing interest in nanoscale forms of such oxides which emanates from the novel changes in their properties with size. To obtain nanomaterials with a high degree of crystallinity it is desirable to first make crystalline oxide powders by high temperature processing and then mill them down to nanometer size. In this paper we show that simple citric acid treatment of BiFeO3 and Bi2O3 powders leads to the desired micron-scale to nanoscale transformation, yielding nearly monodispersed nanoparticles. Importantly, these are highly dispersible and stable in water. By performing similar experiments on Fe3O4 and Fe2O3 we have elucidated the possible mechanism, which hinges on valence-controlled dissolution and ripening phenomena.
Bulletin of the American …, 2011
Recently, rare-earth orthoferrites have received much attention. Their propensity for multiferroi... more Recently, rare-earth orthoferrites have received much attention. Their propensity for multiferroic capabilities could play a key role in the fabrication of an efficient spintronic system. Such materials as BiFeO3 and CeFeO3 have already shown promise for uses in microphotonics as well ...
Applied Physics Letters, 2012