Browsing by Author "R, Dhanasekaran"

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EFFECT OF SHI IRRADIATION ON NBT–BT CERAMICS: TRANSFORMATION OF RELAXOR FERROELECTRIC TO FERROELECTRIC NATURE
(Elsevier, 2013) S, Shanmuga Sundari; Binay Kumar; K, Asokan; R, Dhanasekaran
The lead free NBT–BT ceramics prepared by conventional solid state reaction method were irradiated with 120 MeV Au9+ ions with different fluences. The structural, dielectric and piezoelectric studies were carried out before and after irradiation. The agglomeration and increase of grain size are observed in SEM analysis after the irradiation. The diffuse phase transition disappeared after high fluence of irradiation and the material becomes ferroelectric in nature. The piezoelectric properties were decreased due to the reduced stability of the ferroelectric domains after the irradiation.
GROWTH OF CE ADDED NBT-BT SINGLE CRYSTAL BY FLUX METHOD AND ITS CHARACTERIZATION
(AIP, 2013) S, Shanmuga Sundari; R, Dhanasekaran
The ferroelectric properties and piezoelectric properties are enhanced by the addition of CeO2. CeO2 in the 0.94Na0.5Bi0.5TiO3−0.06BaTiO3 (NBT-BT). 0.4 wt% of CeO2. CeO2 added NBT-BT crystals were grown by flux method.X-ray diffraction studies show that the Ce ion diffuses into the NBT-BT lattice to form a solid solution. Temperature dependence of dielectric constant for the frequency range 20 Hz-2 MHz is studied. Due to the addition of CeO2 the dielectric loss is found to be 1.1 for 1kHz. The diffuseness parameter is found to be 1.82.
INFLUENCE OF TRANSITION METAL IONS ON MULTIFERROIC PROPERTIES OF LEAD-FREE NBT–BT CERAMICS
(World Scientific, 2019) S, Shanmuga Sundari; R, Dhanasekaran
Using the conventional solid-state reaction method, 0.5wt.% of MnO2-, NiO-, Cr2O3-, Fe2O3- and Co2O3-added 0.94Na0.5Na0.5Bi0.5Bi0.5TiO3 (NBT)–0.06BaTiO3 (BT) ceramics were prepared. The perovskite nature of the prepared ceramics was analyzed by powder XRD and the surface morphology was studied by means of SEM. The dielectric analysis was carried out from room temperature to 350∘350∘C at various frequencies and the diffusive transition at the dielectric maxima confirmed the relaxor nature of the ceramics. Creation of oxygen vacancies by the possible substitution of ferromagnetic impurities decreased the dielectric constant and piezoelectric constant (d33)d33). The co-existence of ferromagnetism and the ferroelectricity was observed in the Mn, Ni, Co and Cr-added NBT–BT ceramics. The magnetic force microscopy (MFM) analysis was carried out to study the ferromagnetic domains in the prepared ceramic.
PURE AND ND ADDED NBT-BT SINGLE CRYSTALS-GROWTH AND THEIR CHARACTERIZATION
(AIP, 2014) S, Shanmuga Sundari; K, Baskar; R, Dhanasekaran
The lead free piezoelectric materials are secured an important place in the field of material science and engineering. In the present work single crystals of sodium bismuth titanate- barium titanate (0.94NBT-0.06BT) and 0.6 wt % of Nd added NBT-BT has been grown by flux method. The addition of 0.6 wt% of Nd shows the inhomogeneity in melt and the crystals collected from the top, middle and bottom portions of the crucible have been characterized for their structural and dielectric properties. The Nd concentration is found to be more in the crystals grown from the bottom portion of crucible and it was confirmed by optical and structural analysis. After the addition of Nd the color of the crystal changes form pale yellow to muddy green. The depolarization temperature (Td) and the temperature where the dielectric constant reaches its maximum (Tm) are increased from 442 K to 475 K and 595 K and 628 K respectively after the addition the of Nd in NBT-BT.
REDUCTION OF ANTI-FERROELECTRIC TEMPERATURE REGION IN NBT-BT CERAMICS USING 100 MEV O7+ ION IRRADIATION
(Elsevier, 2014) S, Shanmuga Sundari; Ramaswamy Murugan; K, Asokan; R, Dhanasekaran
NBT-BT (sodium bismuth titanate-barium titanate) lead-free ceramics were prepared via the conventional solid-state reaction method in the Morphotropic Phase Boundary (MPB) composition. The prepared ceramics were irradiated with 100 MeV O7+ ions using four different fluences of 5 × 1011, 1 × 1012, 5 × 1012 and 1 × 1013 ions/cm2. The dielectric constants of the pristine and irradiated samples were determined from 300 to 623 K for a broad range of frequencies from 20 Hz to 2 MHz. Irradiation with oxygen ions decreased the anti-ferroelectric temperature region present in the samples. The structural stability of the samples against the irradiation was investigated via XRD and Raman spectroscopy before and after the irradiation.
STRUCTURAL, DIELECTRIC, PIEZOELECTRIC AND FERROELECTRIC CHARACTERIZATION OF NBT-BT LEAD-FREE PIEZOELECTRIC CERAMICS
(IOP Sciences, 2013) S, Shanmuga Sundari; Binay Kumar; R, Dhanasekaran
Lead free piezoelectric 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 (NBT-BT) ceramics were synthesized in MPB composition by conventional solid state reaction method. The crystalline nature of NBT-BT ceramic was studied by XRD and the size of the grains are determined by SEM. The X- ray diffraction results reveal that Ba2+ diffuse into the Na0.5 Bi0.5TiO3 lattices to form a solid solution with a pure perovskite structure. Because of the strong ferroelectricity and MPB, the ceramics exhibit high piezoelectric properties: d33 = 206 pC/N. Td (depolarization temperature) and Tm (temperature at with the dielectric constant r reaches a maximum) were observed through the phase transition in dielectric studies. In addition, the prepared ceramic exhibits relaxor characteristic, which probably results from the cation disordering in the 12fold coordination sites. Pr and Ec of the prepared ceramics were determined from the P-E hysteresis loop.
SYNTHESIS, DIELECTRIC AND RELAXATION BEHAVIOR OF LEAD FREE NBT–BT CERAMICS
(Elsevier, 2013) S, Shanmuga Sundari; Binay Kumar; R, Dhanasekaran
The 0.94(Na0.5Bi0.5TiO3)–0.06BaTiO3 ceramics have been prepared by the conventional solid state reaction method. Structural analysis of the prepared ceramic was made by means of room temperature XRD, FT-IR and Raman spectra. The formation of perovskite structure is confirmed by XRD and Raman studies. The dependence of dielectric constant on temperature for various frequencies (100 Hz–1.2 MHz) has been determined. The diffuse transition is observed in the variation of dielectric constant and it provides evidence for the relaxor characteristics. The relaxation mechanism of the prepared ceramic is also discussed in detail by using Debye, V–F and Power law relations and the suitable model was predicted by means of goodness of parameter. This is the first time the relaxation process is discussed for the lead free system to the best of our knowledge. High piezoelectric properties with d33=206 pC/N are observed in the present system.