Center for Intelligent Material Systems and Structures (CIMSS)

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Browsing Center for Intelligent Material Systems and Structures (CIMSS) by Author "Gupta, Sanjay"

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    Fatigue mechanism of textured Pb(Mg1/3Nb2/3)O-3-PbTiO3 ceramics
    Yan, Y. K.; Zhou, Y.; Gupta, Sanjay; Priya, Shashank (AIP Publishing, 2013-08-01)
    Grain orientation, BaTiO3 heterogeneous template content, and electrode materials are expected to play an important role in controlling the polarization fatigue behavior of < 001 > textured Pb(Mg1/3Nb2/3)O-3-PbTiO3 ceramics. A comparative analysis with randomly oriented ceramics showed that < 001 > grain orientation/texture exhibits improved fatigue characteristics due to the reduced switching activation energy and high domain mobility. The hypothesis was validated from the systematic characterization of polarization-electric field behavior and domain wall density. The defect accumulation at the grain boundary and clamping effect arising from the presence of BaTiO3 heterogeneous template in the final microstructure was found to be the main cause for polarization degradation in textured ceramic. (C) 2013 AIP Publishing LLC.
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    Ferroelectric properties and dynamic scaling of < 100 > oriented (K0.5Na0.5)NbO3 single crystals
    Gupta, Sanjay; Priya, Shashank (AIP Publishing, 2011-06-01)
    In this letter, we report the dielectric and ferroelectric (FE) characteristics of potassium sodium niobate (K0.5Na0.5NbO3) single crystals grown by flux method. Orientation analysis of as-grown cubical-shaped crystals was conducted by electron backscattered diffraction technique revealing the < 100 > crystallographic orientation of two opposing major faces. Annealed crystals were found to exhibit FE orthorhombic to FE tetragonal transition temperature of 200 degrees C and Curie temperature of 407 degrees C. Poled < 100 > oriented crystals had longitudinal piezoelectric constant of 148 pC/N. Dielectric measurement as a function of temperature was conducted to determine the second order parameter in Gibbs free energy expansion. Dynamic hysteresis analysis on these crystals showed the power law relations to be of the form < A > proportional to f(0.47Eo-0.85)E(o)(1.45f0.14) and < A > proportional to f(0.04)E(o) below and above the coercive field. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600058]
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    High thermal stability of piezoelectric properties in (Na0.5Bi0.5TiO3)(x)-(BaTiO3)(y)-(Na0.5K0.5NbO3)(1-x-y) ceramics
    Gupta, Sanjay; Priya, Shashank (AIP Publishing, 2013-01-01)
    We report the piezoelectric and ferroelectric properties of (Na0.5Bi0.5TiO3)(x)-(BaTiO3)(y)-(Na0.5K0.5NbO3)(1-x-y) ceramics for Na0.5K0.5NbO3 rich end of composition (x, y <= 0.04 mol. %). These compositions were found to exhibit significantly improved thermal stability of piezoresponse. Variation of dielectric constant as a function of temperature revealed that orthorhombic-tetragonal (To-t) and tetragonal-cubic (T-c) transition temperatures for these compositions were in the vicinity of 0 degrees C and 330 degrees C, respectively. Dynamic scaling and temperature dependent X-ray diffraction analysis were conducted. Results are discussed in terms of intrinsic and extrinsic contributions to the piezoelectric response explaining the temperature dependent behavior. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773983]