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    Diluted magnetism in Mn-doped SrZnO2 single crystals
    (American Institute of Physics Inc., 2013) Rahman, M.R.; Koteswararao, B.; Huang, S.H.; Kim, K.; Chou, F.C.
    We have investigated the magnetic properties of Mn- and Cu-substituted SrZnO2 single crystals (SrZn1-xMnxO2 and SrZn1-xCuxO2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the low-percentage (x = 0.01) of Mn-substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab-plane yield anisotropic behavior with Curie-Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn at high temperatures, similar to the Mn-doped ZnO and Fe-doped BaTiO3. In contrast, the SrZn0.99Cu0.01O 2 crystal shows paramagnetic behavior down to 2 K. © 2013 AIP Publishing LLC.
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    Dielectric and piezoelectric properties of PVDF/PZT composites: A review
    (John Wiley and Sons Inc, 2015) Jain, A.; Prashanth, K.J.; Sharma, A.K.; Jain, A.; P.n, R.
    Smart materials, which exhibit piezoelectricity, find an eclectic range of applications in the industry. The direct piezoelectric effect has been widely used in sensor design, and the inverse piezoelectric effect has been applied in actuator design. Ever since 1954, PZT and BaTiO3 were widely used for sensor and actuator applications despite their toxicity, brittleness, inflexibility, etc. With the discovery of PVDF in 1969, followed by development of copolymers, a flexible, easy to process, nontoxic, high density alternate with high piezoelectric voltage coefficient was available. In the past 20 years, heterostructural materials like polymer ceramic composites, have received lot of attention, since these materials combine the excellent pyroelectric and piezoelectric properties of ceramics with the flexibility, processing facility, and strength of the polymers resulting in relatively high dielectric permittivity and breakdown strength, which are not attainable in a single phase piezoelectric material. The current review article is an attempt to provide a compendium of all the work carried out with reference to PVDF-PZT composites. The review article evaluates the effect of grain size, content and other factors under the purview of dielectric and piezoelectric properties while evaluating the sensitivity of the material for sensor application.
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    Hierarchical porous Batio3 nano-hexagons as a visible light photocatalyst
    (Science Publishing Corporation Inc ijet@sciencepubco.com, 2018) Bantawal, H.; Bhat, D.K.
    Hierarchical porous BaTiO3 nano-hexagons was synthesized via a simple hydrothermal route by using TiO2 and Ba(OH)2.8H2O as starting materials under alkaline environment and its photocatalytic activity was evaluated under visible light by taking methylene blue (MB) as a model pollutant. The prepared BaTiO3 was characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-rays analysis (EDX), high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) analysis and diffused reflectance spectroscopy (DRS) techniques. It is noteworthy that the BaTiO3 nanohexagons exhibited significant photocatalytic activity towards the degradation of MB under visible light irradiation. This significant photocatalytic activity of BaTiO3 under visible light is mainly attributed to the special morphology and formation of Ti3+ defects. © 2018 Authors.
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    Investigation of the effect of BaTiO3/CoFe2O4 particle arrangement on the static response of magneto-electro-thermo-elastic plates
    (Elsevier Ltd, 2018) Mahesh, M.; Kattimani, S.
    In this article, a framework based on finite element (FE) methods is proposed for predicting the influence of spatial arrangement of two phase Barium Titanate (BaTiO3) and Cobalt Ferric Oxide (CoFe2O4) particulate composites on the static response of magneto-electro-thermo-elastic (METE) plates. The coupled material properties such as piezoelectric, piezomagnetic, dielectric, magnetic permeability, thermal expansion and pyro co-efficients vary significantly with the spatial arrangement of BaTiO3/CoFe2O4 particulates. The coupled FE governing equations accounting the effect of particle arrangement is presented by incorporating linear coupled constitutive equations of METE composites. Through the condensation technique, the governing equations of METE plates are solved to obtain direct (thermal displacements, electric and magnetic potentials) and derived quantities (stresses, electric displacements and magnetic flux densities). A special attention has been placed on evaluating the pyro-electric and pyro-magnetic coupling effects for different packing arrangement considered namely, Body Centered Cubic (BCC), Face Centered Cubic (FCC) and Simple Cubic (SC) METE particulate composites. Further, parametric studies are carried out to analyse the influence of boundary conditions and aspect ratio. The present study reveals that the multiphysics response of METE plates changes significantly with the packing arrangements of BaTiO3/CoFe2O4 particulates and geometrical parameters. It is believed that the obtained solutions would provide insights into design aspects of METE structures. © 2017 Elsevier Ltd
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    Vibration control of multiferroic fibrous composite plates using active constrained layer damping
    (Academic Press, 2018) Kattimani, S.; Ray, M.C.
    Geometrically nonlinear vibration control of fiber reinforced magneto-electro-elastic or multiferroic fibrous composite plates using active constrained layer damping treatment has been investigated. The piezoelectric (BaTiO3) fibers are embedded in the magnetostrictive (CoFe2O4) matrix forming magneto-electro-elastic or multiferroic smart composite. A three-dimensional finite element model of such fiber reinforced magneto-electro-elastic plates integrated with the active constrained layer damping patches is developed. Influence of electro-elastic, magneto-elastic and electromagnetic coupled fields on the vibration has been studied. The Golla–Hughes–McTavish method in time domain is employed for modeling a constrained viscoelastic layer of the active constrained layer damping treatment. The von Kármán type nonlinear strain-displacement relations are incorporated for developing a three-dimensional finite element model. Effect of fiber volume fraction, fiber orientation and boundary conditions on the control of geometrically nonlinear vibration of the fiber reinforced magneto-electro-elastic plates is investigated. The performance of the active constrained layer damping treatment due to the variation of piezoelectric fiber orientation angle in the 1–3 Piezoelectric constraining layer of the active constrained layer damping treatment has also been emphasized. © 2018 Elsevier Ltd
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    Effect of BaTiO3/CoFe2O4 micro-topological textures on the coupled static behaviour of magneto-electro-thermo-elastic beams in different thermal environment
    (Institute of Physics Publishing helen.craven@iop.org, 2018) Mahesh, M.; Kattimani, S.C.; Loja, M.A.R.; Mahesh, V.
    The use of composite materials with multifunctional capabilities is an increasing requirement for structures or components where the sensory function is accompanied by the diagnosis and the actuation functions, such as autonomic, adaptive or self-sustaining systems. In this context, the present study aims to characterize the coupled response of magneto-electro-thermo-elastic (METE) beams made from Barium Titanate (BaTiO3) and Cobalt Ferric Oxide (CoFe2O4) composite having various micro-topological textures, as well as their static response when submitted to different temperature distribution profiles. To this purpose, a three-dimensional finite element accounting for the coupling between the multiple physical fields in presence, is developed and implemented. The spatial heterogeneous BaTiO3/CoFe2O4 microstructure is also assessed by considering typical Body Centered Cubic (BCC), Face Centered Cubic (FCC) and Simple Cubic (SC) spatial packing arrangements. A special attention is paid to the influence of these micro-topological structures on the pyroeffects and its contribution towards the direct and derived quantities of the METE beam. The results obtained, suggest that the composite heterogeneous microstructure have a relevant influence on the static response of the METE beam in thermal environment. © 2018 IOP Publishing Ltd.
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    Finite element simulation of controlled frequency response of skew multiphase magneto-electro-elastic plates
    (SAGE Publications Ltd info@sagepub.co.uk, 2019) Mahesh, M.; Kattimani, S.
    The linear frequency response of skew multiphase magneto-electro-elastic composite plate embedded with active constrained layer damping treatment has been studied. The volume fraction of piezoelectric fibres embedded in the piezomagnetic matrix significantly affects the coupling characteristic of this multiferroic material, and hence, the frequency of the skew multiphase magneto-electro-elastic plate is drastically altered. This study emphasizes on evaluating the influence of different volume fraction of barium titanate (BaTiO3) and cobalt ferrite (CoFe2O4) on the frequency characteristics of skew multiphase magneto-electro-elastic. In this regard, a finite element formulation has been proposed to assess the damped response of such skew multiphase magneto-electro-elastic plates. Incorporating the complex modulus approach, the constrained viscoelastic layer of the active constrained layer damping patch is modelled. In addition, the effect of geometrical skewness has also been investigated. Meanwhile, an exhaustive parametric study is carried out to analyse the influence of control gain, patch position and fibre orientation angle of piezoelectric composite. © The Author(s) 2019.
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    Influences of dielectric and conductive fillers on dielectric and mechanical properties of solid silicone rubber composites
    (Springer London, 2019) Manohar Shankar, B.S.; Kulkarni, S.M.
    Dielectric elastomers are materials being used for electromechanical transduction applications. Their electromechanical response depends on permittivity, Young’s modulus and electric breakdown strength. A factor that limits its application is high operating voltages that can be reduced through improvement in permittivity. One of the methods is by incorporating high permittivity fillers into polymer matrix to obtain dielectric–dielectric composites (DDC).These composites show high permittivity at the cost of reduced flexibility. An alternative solution is development of composites by incorporating organic or inorganic conductive fillers into polymer matrix. These composites show high permittivity with high dielectric loss and low breakdown strength. To overcome both the above limitations both dielectric and conductive fillers are incorporated into dielectric polymer matrix to obtain conductor–dielectric composites (CDC). In this study, high temperature vulcanized solid silicone rubber as matrix has been used to prepare DDC composites with barium titanate (BT) filler and CDC composites with both BT as dielectric and ketjenblack as conductive fillers, using Taguchi design of experiments. The effect of factors such as amount of fillers and curing agent, mixing time in roll mill and curing temperature on the dielectric and mechanical properties are reported. Lichtenecker model predicts the permittivity of the DDC composite more accurately. For the CDC composites permittivity increased by 390%, effective resistivity decreased by 80%, Young’s modulus increased by 368% and Shore A hardness increased by 90% as compared to those of reference matrix. Important interaction effects are observed among both the fillers that are uniformly dispersed without any aggregation. © 2019, Iran Polymer and Petrochemical Institute.
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    Vanadium-doped BaTiO3 as high performance thermoelectric material: role of electronic structure engineering
    (Elsevier Ltd, 2020) Shenoy, U.S.; Bhat, D.K.
    It is well known that thermoelectric (TE) materials are the most sought-after ones to mitigate energy crisis. Development of an efficient non-toxic, economic, abundant, and stable TE material is quite difficult due to its complicated traits. BaTiO3, a perovskite material shows a tremendous potential as a TE material due to its highly tunable electronic structure. Herein, for the first time we report use of dopant to improve the Seebeck coefficient of BaTiO3. We used first-principles density functional theory calculations to study the effect of vanadium doping in BaTiO3, and for the first time, we report that V acts as a resonant dopant in BaTiO3. The study on effect of site occupancy reveals that V in Ba site distorts the density of states below the conduction band by introducing resonance level at the Fermi level. The transport property calculations based on Boltzmann's relation predicts V-doped BaTiO3 to be a potential TE material. The results also provide new insights into development of BaTiO3 as a multifunctional material. © 2020 Elsevier Ltd
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    Rhodium doping augments photocatalytic activity of barium titanate: Effect of electronic structure engineering
    (Royal Society of Chemistry, 2020) Bhat, D.K.; Bantawal, H.; Shenoy, U.S.
    Environmentally friendly BaTiO3 is emerging as a potential photocatalyst due to its tunable electronic structure. Although originally believed to be a poor photocatalyst due to its wide band gap, several strategies have been implemented to reduce its band gap. One such approach is doping, but this often leads to the formation of mid gap recombination centers and diminishes the efficiency of the material. In the present work, we study for the first time the effect of site occupancy of Rh on the electronic structure of BaTiO3. As the theoretical results reveal that if Rh occupies both Ba and Ti sites simultaneously it leads to the formation of mid gap states, an experimental approach is implemented to reduce the band gap of BaTiO3 while simultaneously avoiding the formation of recombination centers. The facile one pot hydrothermal approach reported here directs the Rh towards Ba sites leading to a decrease in the band gap due to the appearance of donor Rh3+ states, suppressing the formation of Rh4+ states. A promising photocatalytic activity of 96% degradation of methylene blue dye in 120 minutes was observed for the 0.5 Rh sample indicating the high efficiency of the material. © The Royal Society of Chemistry.