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Synthesis and characterization of spin-coated clay/PVDF thin films
摘要： This paper reports the fabrication of Cloisite-15A (C-15A)-dispersed polyvinylidene fluoride (PVDF) nanocomposite thin films by spin coating and their characterization for sensor applications. The effects of nanoclay, duration of ultrasonication and spinning speed on the morphology and properties of thin films were studied. The influence of these parameters on the amount of β-phase was analysed using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) techniques. The influence of C-15A on the morphology and surface quality of thin films was analysed by scanning electron microscopy (SEM). Piezoelectric coefficient was measured at 110 Hz and 0.25 N. Contact angle was measured to assess the hydrophobicity of thin films. The β-phase of 82.97% was obtained in the specimens with 5 wt% C-15A, processed at 500 rpm and spun for 35 min. The piezoelectricity of the specimens increased from ?18 to ?25 pC N?1. Experiments were conducted as per L16 orthogonal array.
关键词： spin coating,Cloisite-15A,β-crystals,PVDF/clay thin films,piezoelectricity
更新于2025-09-23 15:22:29
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Dispersion of Love waves in size-dependent substrate containing finite piezoelectric and viscoelastic layers
摘要： The dispersion properties of Love waves are utilized for the fabrication of sensor devices in the different material environments. This study involves the propagation of Love wave in a double-layered structure consisting of two finite layers of viscoelastic and piezoelectric material lying over the semi-infinite size-dependent micropolar substrate. The bottom substrate of the structure is modeled as, the material with microstructural properties. The real and damping dispersion relations are obtained analytically in closed form expression under both the cases of electrically open and short conditions. The coupling constant and characteristic length that describe the effect of the microstructure of the micropolar substrate, are studied graphically on Love wave propagation. The effects of piezoelectric layer are shown by considering two different materials of a piezoelectric layer, i.e., PZT-5H or BaTiO3, along with the internal friction and heterogeneity parameter associated with a viscoelastic layer. The numerical computation and the graphs are given for aluminium-epoxy (substrate), viscoelastic material and PZT-5H or BaTiO3 (piezoelectric layer). Some of the particular cases are derived from the study by using different relevant conditions.
关键词： Viscoelastic,Piezoelectricity,Dispersion relations,Heterogeneity,Micropolar,Love wave,Characteristic length
更新于2025-09-23 15:22:29
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Electrical Properties and Thermal Expansion Characteristics of (1- <i>x</i> )Ba <sub/>0.948</sub> Ca <sub/>0.05</sub> Er <sub/>0.002</sub> Ti <sub/>0.94</sub> Zr <sub/>0.06</sub> O <sub/>3</sub> -( <i>x</i> )Pr Lead-Free Piezoelectric Ceramics Sintered at a Low-Temperature
摘要： (1 (cid:1) x)Ba0.948Ca0.05Er0.002Ti0.94Zr0.06O3–(x)Pr (x ? 0–0.75 mol%) ceramics are sintered at 1240 (cid:3)C by conventional solid-state reaction method using the as-synthesized nanoparticles, which are prepared by a modified Pechini method. The structural, morphological, electrical, and thermal expansion properties as a function of varying x are systematically investigated. All samples feature rhombohedral phase, and their lattice parameters are accurately calculated by Rietveld refinement software. Volume of oxygen vacancies initially decreases and then increases with increasing x, leading to diversified electrical properties. Deteriorated electrical properties of the ceramics with excessive x are attributed to the increment of defect complexes with a large volume of oxygen vacancies. The coefficient of thermal expansion values of the ceramics that is influenced by phase evolution and structure defects under different temperature ranges are studied. The respective optimal electrical properties, that is, d33 ? 186 pC N mol%. This research is believed to be insightful to practical application of the lead-free multifunctional electron components.
关键词： thermal expansion coefficient,defect complexes,praseodymium-doping,BCEZT ceramics,piezoelectricity
更新于2025-09-23 15:21:21
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Tweaking the physics of interfaces between monolayers of buckled cadmium sulfide for a superhigh piezoelectricity, excitonic solar cell efficiency and thermoelectricity
摘要： Interfaces of heterostructures are routinely studied for different applications. Interestingly, monolayers of the same material when interfaced in an unconventional manner can bring about novel properties. For instance, CdS monolayers, stacked in a particular order, are found to show unprecedented potential in the conversion of nanomechanical energy, solar energy and waste heat into electricity, which has been systematically investigated in this work, using DFT based approaches. Moreover, stable ultrathin structures showing strong capabilities for all kinds of energy conversion are scarce. The emergence of a very high out-of-plane piezoelectricity, |d33| ~ 56 pm/V, induced by the inversion symmetry broken in the buckled structure helps to supersede the previously reported bulk wurzite GaN, AlN and Janus multilayer structures of Mo and W based dichalcogenides. The piezoelectric coefficients have been found to be largely dependent on the relative stacking between the two layers. CdS bilayer is a direct band gap semiconductor with its band edges straddling the water redox potential, thereby making it thermodynamically favorable for photocatalytic applications. Strain engineering facilitates its transition from type-I to type-II semiconductor in CdS bilayer stacked over monolayer boron phosphide, and the theoretically calculated power conversion efficiency (PCE) in the 2D excitonic solar cell exceeds 27% for a fill factor of 0.8, which is much higher than that in ZnO/CdS/CuInGaSe solar cell (20% efficiency). Thermoelectric properties have been investigated using semi classical Boltzmann transport equations for electrons and phonons within the constant relaxation time approximation coupled to deformation potential theory, which reveal ultralow thermal conductivity (~ 0.78 Wm-1K-1) at room temperature due to the presence of heavy element Cd, strong anharmonicity (high mode Gruneisen parameter at long wavelength, phonon lifetime < 5 ps), low phonon group velocity (4 km/s) and low Debye temperature (260 K). Such a low thermal conductivity is lower than that of dumbbell silicene (2.86 Wm-1K-1), SnS2 (6.41 Wm-1K-1) and SnSe2 (3.82 Wm-1K-1), SnP3 (4.97 Wm-1K-1). CdS bilayer shows a thermoelectric figure of merit (ZT) ~ 0.8 for p-type and ~ 0.7 for n-type doping at room temperature. Its ultrahigh carrier mobility (μe ~2270 cm2V-1s-1) is higher than that of single layer MoS2 and comparable to that in InSe. The versatile properties of CdS bilayer together with its all-round stability supported by ab initio molecular dynamics simulation, phonon dispersion and satisfaction of Born-Huang stability criteria highlight its outstanding potential for applications in device fabrication and applications in next generation nanoelectronics and energy harvesting.
关键词： Power conversion efficiency,Excitonic solar cell,Piezoelectricity,Photocatalysis,Solar energy,Semiconductor,Thermoelectricity,Carrier mobility
更新于2025-09-23 15:21:01
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Superhigh flexibility and out-of-plane piezoelectricity together with strong anharmonic phonon scattering induced extremely low lattice thermal conductivity in hexagonal buckled CdX (X= S, Se) monolayers
摘要： Although CdX (X= S, Se) has been mostly studied in the field of photocatalysis, photovoltaics, their intrinsic properties, such as, mechanical, piezoelectric, electron and phonon transport properties have been completely overlooked in buckled CdX monolayers. Ultra-low lattice thermal conductivity (1.08 W/mK (0.75 W/mK)) and high p-type Seebeck coefficient (1300 μV/K (850 μV/K)) in CdS (CdSe) monolayers have been found in this work based on first-principles DFT coupled to semi-classical Boltzmann transport equations, combining both the electronic and phononic transport. The dimensionless thermoelectric figure of merit (ZT) is calculated to be 0.78 (0.5) in CdS (CdSe) monolayers at room temperature, which is comparable to that of 2D tellurene (0.8), arsenene and antimonene (0.8), indicating its great potential for applications in 2D thermoelectrics. Such a low lattice thermal conductivity arise from the participation of both acoustic [91.98 % (89.22 %)] and optical modes [8.02 % (10.78 %)] together with low Debye temperature [254 K (187 K)], low group velocity [4 km/s (3 km/s)] in CdS (CdSe) monolayers, high anharmonicity and short phonon lifetime. Substantial cohesive energy (~ 4-5 eV), dynamical and mechanical stability of the monolayers substantiate the feasibility in synthesizing the single layers in experiments. The inversion symmetry broken along the ?? direction causes out-of-plane piezoelectricity. |d33| ~ 21.6 pm/V, calculated in CdS monolayer is found to be the highest amongst structures having atomic-layer thickness. Superlow Young’s modulus ~ 41 N/m (31 N/m) in CdS (CdSe) monolayers, which is comparable to that of planar CdS (29 N/m) and TcTe2 (34 N/m), is an indicator of its superhigh flexibility. Direct semiconducting band gap, high carrier mobility (~ 500 cm2V-1s-1) and superhigh flexibility in CdX monolayers signify its gigantic potential for applications in ultrathin, stretchable and flexible nanoelectronics. The all-round properties can be synergistically combined together in futuristic applications in nano-piezotronics as well.
关键词： thermoelectrics,flexible nanoelectronics,phonon transport,CdX monolayers,piezoelectricity
更新于2025-09-23 15:21:01
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A size-dependent micropolar-piezoelectric layered structure for the analysis of love wave
摘要： The propagation characteristics of Love wave form an essential basis for designing highly sensitive microacoustic devices for sensing applications. In this paper, the propagation of Love wave in a micropolar-piezoelectric structure is investigated with the objective of enhancing the performance of Love wave-based devices. A study has been carried out by using two sets of a piezoelectric material, i.e. PZT-5H and BaTiO3 material. The closed-form expression of the dispersion relations is derived analytically for electrically open and electrically short conditions. The effects of internal microstructures of the micropolar elastic half-space, the thickness of a piezoelectric layer, the piezoelectric constants, and the dielectric constants are illustrated graphically on the phase velocity for both the considered materials of the piezoelectric layer under electrically open and short conditions.
关键词： Piezoelectricity,Love wave,micropolar,characteristic length,dispersion relation
更新于2025-09-23 15:21:01
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Stability, spontaneous and induced polarization in monolayer MoC, WC, WS, and WSe
摘要： Using density functional theory based calculations, we design buckled honeycomb binary monolayer MoC, WC, WS, and WSe. The feasibility of their experimental synthesis is evident from their low formation energies, stable lattice vibrations, and high elastic stiffnesses. The difference in electronegativity of the building atoms and lack of inversion symmetry results in high spontaneous out-of-plane polarization whereas all the in-plane components cancel out. The existence of the mirror plane along the armchair direction vanishes the in-plane piezoelectric stress effects for a strain applied along the zigzag direction. However, a strain along the armchair direction on MoC and WC results in a high piezoelectric coefficient up to 10×10?10 C/m, about three times larger than that reported for monolayer MoS2. The polarization switching barriers for the out-of-plane components range from 0.55 to 2.70 eV per formula unit.
关键词： ferroelectricity,monolayer,density functional theory,polarization,piezoelectricity
更新于2025-09-23 15:21:01
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Highly selective and label-free Love-mode surface acoustic wave biosensor for carcinoembryonic antigen detection using a self-assembled monolayer bioreceptor
摘要： A love-mode surface acoustic wave (SAW) biosensor based on ST-cut quartz was developed for highly selective and label-free detection of carcinoembryonic antigen (CEA). The delay line area of an interdigital transducer (IDT) based SAW device was coated with gold and then chemically modified through thioglycolic acid–EDC/NHS reaction mechanism. A self-assembled monolayer of anti-CEA was further immobilized on the bioreceptors through the coupling layer. The biosensing capability of the SAW device was evaluated using solutions of CEA with various concentrations and limit of detection was obtained at 0.31 ng/ml of CEA, which is better than the results reported by the literatures available for CEA detection using SAW device. The real-time detection capability of the biosensor was evaluated using clinical serum samples and selectivity was evaluated using mixed solutions of CEA with other common tumor marking proteins. Long-term stability of the biosensor was also evaluated over a period of 30 days and the immunoassay response has shown only 8% decrease in performance within the whole period. The binding of CEA onto the bioreceptor was evaluated through Langmuir and Freundlich sorption isotherm kinetic studies as well.
关键词： SAW,Piezoelectricity,Biosensing,CEA,Label free,SAM
更新于2025-09-23 15:19:57
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Nanoscale Interfaces of Janus Monolayers of Transition Metal Dichalcogenides for 2D Photovoltaic and Piezoelectric Applications
摘要： Using first-principles calculations, we demonstrate a combination of two emergent fields, type-II van der Waal heterostructures and Janus structures, for the purpose of optimizing the harvesting of solar and nanoelectromechanical energy. The most stable stacking order in these nanoscale heterobilayers comprising of Janus monolayers of transition metal dichalcogenides has been ascertained based on the interlayer binding energies. The binding energies in WSeTe/WSTe and MoSeTe/WSTe heterobilayers are found to be -27.93 and -25.67 meV/?2 at an equilibrium interlayer layer distance of 3.25 ? and 3.32 ? respectively, indicating the exothermicity in the process of heterobilayer formation and hence, its experimental feasibility. The mechanical and dynamical stabilities have also been confirmed for these heterobilayers using the Born Huang stability criteria and phonon dispersion calculations. Our results unveil the mechanism underlying the electronic, piezoelectric, photocatalytic properties and carrier mobility in these Janus heterobilayers. Power conversion efficiency in the 2D ultrathin excitonic solar cells constituted by some of the heterobilayers studied in this work, has been found to lie in the range of 15-20%. Moreover, a very high carrier mobility (>200 cm2/V.s) together with a large visible light absorption coefficient (α ~ 105 cm-1) has been observed in these hetero-bilayers. The piezoelectric coefficients in these ultrathin heterobilayers (d33 = 13.91 pm/V) is found to reach close to the values obtained in multilayer/bulk structures built from Janus monolayers of Mo-based dichalcogenides. Our findings highlight the promising applications of these heterobilayers in ultrathin excitonic solar cells, nanoelectronics and nanopiezotronics.
关键词： van der Waals heterostructures,transition metal dichalcogenides,photovoltaic applications,Janus monolayers,piezoelectricity,carrier mobility
更新于2025-09-23 15:19:57
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Hierarchically decomposed finite element method for a triply coupled piezoelectric, structure, and fluid fields of a thin piezoelectric bimorph in fluid
摘要： This paper proposes a numerical method for analyzing a thin piezoelectric bimorph in fluid. A hierarchically decomposed finite element method (FEM) is proposed for modeling the triply coupled piezoelectric-structure–fluid interaction. The electromechanical coupling (piezoelectric-structure interaction) behavior in a thin piezoelectric bimorph is described by the classical constitutive equation, the incompressible fluid flows by the Navier–Stokes equation and the structure by the Cauchy equation of motion. The piezoelectric-structure–fluid interaction system is decomposed into subsystems of fluid–structure interaction (FSI) and piezoelectric field, then the piezoelectric field and the FSI are coupled using the block Gauss–Seidel method, the fluid–structure interaction is split into the fluid–structure velocity field and the pressure field using an algebraic splitting and the fluid–structure velocity field is partitioned into fluid velocity field and structure velocity field. Using the proposed method, the resonance characteristics of a piezoelectric bimorph cantilever made of PVDF and PZT-5H material in fluid are investigated for actuation and sensor configurations.
关键词： Thin piezoelectric bimorph,Hierarchical decomposition,Finite element method (FEM),Fluid–structure interaction (FSI),Piezoelectricity,Piezoelectric-structure interaction
更新于2025-09-23 15:19:57