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Universal converse flexoelectricity in dielectric materials via varying electric field direction

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International Journal of Smart and Nano Materials 2021年第1期12卷 107-128页

作者： Saurav Sharma Rajeev Kumar rahul vaish School of Engineering Indian Institute of Technology MandiMandiIndia

Flexoelectricity is a symmetry independent electromechanical cou-pling phenomenon that outperforms piezoelectricity at micro and nanoscales due to its size-dependent behavior arising from gradi-ent terms in its constitutive ***,due to this gradient term flexoelectricity,to exhibit itself,requires specially designed geometry or material composition of the dielectric *** of its kind,the present study put forward a novel strategy of achieving electric field gradient and thereby converse flexoelectri-city,independent of geometry and material composition of the *** spatial variation of the electric field is established inside the dielectric material,Ba_(0.67)Sr_(0.33)TiO_(3)(BST),by manipulating electrical boundary *** unique patterns of electrode placement are suggested to achieve this spatial *** varying direction of electric field gives rise to electric field gradient,the prerequisite of converse flexoelectricity.A multi-physics cou-pling based theoretical framework is established to solve the flexo-electric actuation by employing isogeometric analysis(IGA).Electromechanically coupled equations of flexoelectricity are solved to obtain the electric field distribution and the resulting displace-ments *** maximum displacements of 0.2 nm and 2.36 nm are obtained with patterns I and II,respectively,while pattern III can yield up to 85 nm of maximum displacement.

关键词： Converse flexoelectricity electrical boundary conditions electric field direction isogeometric analysis

Effect of Sr_(2) TiMnO_(6) fillers on mechanical, dielectric and thermal behaviour of PMMA polymer

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Journal of Advanced Dielectrics 2015年第3期5卷 1-11页

作者： P.Thomas B.S.Dakshayini H.S.Kushwaha rahul vaish Dielectric Materials Division Central Power Research Institute BangaloreKarnataka 560080India Aerospace Engineering Indian Institute of Science BangaloreKarnataka 560012India School of Engineering Indian Institute of Technology Mandi Himachal Pradesh 175001India

Composites of poly(methyl methacrylate)(PMMA)and Sr_(2) TiMnO_(6)(STMO)were fabricated via melt mixing followed by hot pressing *** were characterized using X-ray diffraction(XRD),thermo gravimetric analysis(TGA),differential scanning calorimetry(DSC),thermo mechanical analysis(TMA)and impedance analyser for their structural,thermal and dielectric *** coefficient of thermal expansion(CTE)was measured between 40℃ and 100℃ for pure PMMA is 115.2ppm/℃,which was decreased to 78.58ppm/℃ when the STMO content was increased to 50 wt.%in *** was no difference in the glass transition(T g)temperature of the PMMA polymer and their ***,the FTIR analysis indicated possible interaction between the PMMA and *** density and the hardness were increased as the STMO content increased in the PMMA *** was found to be as high as 30.9 at 100Hz for the PMMAþSTMO-50 wt.%composites,indicating the possibility of using these materials for capacitor *** thermal stability of polymer was enhanced by incorporation of STMO fillers.

关键词： Polymer composite dielectric properties mechanical properties thermal properties

Piezoelectric materials selection for sensor applications using finite element and multiple attribute decision-making approaches

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Journal of Advanced Dielectrics 2015年第1期5卷 21-28页

作者： Anuruddh Kumar Anshul Sharma Rajeev Kumar rahul vaish Vishal S Chauhan C.R.Bowen School of Engineering Indian Institute of Technology Mandi Himachal Pradesh 175001India Department of Mechanical Engineering University of Bath BathBA27AYUK

This paper examines the selection and performance evaluation of a variety of piezoelectric materials for cantilever-based sensor *** finite element analysis method is implemented to evaluate the relative importance of materials properties such as Young's Modulus(E),piezoelectric stress constants(e_(31)),dielectric constant(ε)and Poisson's ratio(ν)for cantilever-based sensor *** analytic hierarchy process(AHP)is used to assign weights to the properties that are studied for the sensor structure under study.A technique for order preference by similarity to ideal solution(TOPSIS)is used to rank the performance of the piezoelectric materials in the context of sensor voltage *** ranking achieved by the TOPSIS analysis is in good agreement with the results obtained from finite element method *** numerical simulations show that K_(0.5)Na_(0.5)NbO_(3)-LiSbO_(3)(KNN-LS)materials family is important for sensor ***'s modulus(E)is most influencing material's property followed by piezoelectric constant(e_(31)),dielectric constant(ε)and Poisson's ratio(ν)for cantilever-based piezoelectric sensor applications.

关键词： Lead-free piezoelectric ceramics finite element modeling analytical hierarchy process material selection

ELECTRICAL TRANSPORT STUDIES IN 3Na_(2)O-6:5B_(2)O_(3) GLASSES

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Journal of Advanced Dielectrics 2011年第3期1卷 331-336页

作者： rahul vaish KALIDHINDI B.R.VARMA Materials Research Centre Indian Institute of Science Bangalore 560012India

Transparent 3Na_(2)O-6:5B_(2)O_(3)(NBO)glasses were fabricated via the conventional melt-quenching technique.X-ray powder difraction(XRD)combined with Differential Scanning Calorimetric(DSC)studies carried out on the as-quenched samples confirmed their amorphous and glassy nature,*** frequency and temperature dependent of the dielectric constant,electric modulus and electrical conductivity of the transparent NBO glasses were investigated in the 100 Hz-10 MHz frequency *** electrical modulus and conductivity data have been rationalized using Jonscher's universal *** bulk dc conductivity at various temperatures was extracted from the electrical relaxation *** activation energy associated with dc conduc-tivity is 0.52±0.01 eV,which is ascribed to the motion of Na^(+)ions in the glass matrix.

关键词： Glass dielectric relaxation conductivity

Giant energy harvesting potential in(100)-oriented 0.68PbMg_(1/3)Nb_(2/3)O_(3)-0.32PbTiO_(3)with Pb(Zr_(0.3)Ti_(0.7))O_(3)/PbO_(x)buffer layer and(001)-oriented 0.67PbMg_(1/3)Nb_(2/3)O_(3)-0.33PbTiO_(3)thin films

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Journal of Advanced Dielectrics 2014年第4期4卷 18-23页

作者： Gaurav Vats Himmat Singh Kushwaha rahul vaish Niyaz Ahamad Madhar Mohammed Shahabuddin Jafar M.Parakkandy Khalid Mujasam Batoo School of Engineering Indian Institute of Technology Mandi Himachal Pradesh 175001 India Department of Physics and Astronomy P.O.Box No.2455 College of SciencesKing Saud University Riyadh 11451Kingdom of Saudi Arabia King Abdullah Institute of Nanotechnology P.O.Box No.2455 King Saud UniversityRiyadh 11451 Kingdom of Saudi Arabia

This work emphasis on the competence of(100)-oriented PMN–PT buffer layered(0.68PbMg_(1/3)Nb_(2/3)O_(3)–0.32PbTiO_(3)with Pb(Zr_(0.3)Ti_(0.7))O_(3)/PbO_(x)buffer layer)and(001)-oriented PMN–PT(0.67PbMg_(1/3)Nb_(2/3)O_(3)–0.33PbTiO_(3))for low grade thermal energy harvesting using Olsen *** analysis(based on well-reported experiments in literature)reveals that these films show colossal energy harnessing *** the films are found to have maximum harnessable energy densities(PMN–PT buffer layered:8 MJ/m^(3);PMN–PT:6.5 MJ/m^(3))in identical ambient conditions of 30–150℃and 0–600 kV/*** energy harnessing plausibility is found to be nearly five times higher than the previously reported values to date.

关键词： Giant energy harvesting thin films Olsen cycle