arXiv subjects

Supratim Mitra

Publications and source records attributed to Supratim Mitra.

7 recordsLinked to original sources

arXiv2025

ZnO@C/PVDF Electrospun Membrane as Piezoelectric Nanogenerator for Wearable Applications

The rapid growth of wearable technology demands sustainable, flexible, and lightweight energy sources for various applications ranging from health monitoring to electronic textiles. Although wearable devices based on the piezoelectric effect are widespread, achieving simultaneous breathability, waterproof, and enhanced piezoelectric performance remains challenging. Herein, this study aims to develop a piezoelectric nanogenerator (PENG) using ZnO nanofillers in two morphologies (nanoparticles and nanorods), with a carbon coating (ZnO@C) core-cell structure to enhance piezoelectric performance. Electrospinning technique was employed to fabricate a lightweight, breathable, and water-resistant ZnO@C/PVDF membrane, enabling in situ electrical poling and mechanical stretching to enhance electroactive \b{eta}-phase formation and thus improve piezoelectric performance. A maximum power density of 384.83 {\mu}W/cm3 was obtained at RL = 104 k{\Omega}, with a maximum Vout = 19.9 V for ZnO@C nanorod-incorporated PVDF samples. The results demonstrate that ZnO@C nanorods exhibit superior voltage output due to their larger surface-to-volume ratio, leading to enhanced interaction with PVDF chains compared to nanoparticles. The fabricated membrane showed promising results with a water vapor transmission rate (WVTR) of ~0.5 kg/m2/day, indicating excellent breathability, and a water contact angle of ~116{\deg}, demonstrating significant waterproofness. These findings highlight the potential of the ZnO@C/PVDF electrospun membrane as an effective piezoelectric nanogenerator and energy harvester for wearable applications.

physics.app-ph↗

arXiv2023

Influence of Solution Parameters on Phase Formation and Morphology of Electrospun Poly(vinylidene fluoride) Nanofiber

Poly(vinylidene fluoride), PVDF nanofibers were prepared using electrospinning method and the influence of electrospinning parameters such as PVDF concentration, DMF:Acetone ratio on the formation of different phases (α, \b{eta}, and γ) and desired morphology were investigated. A detail analysis of X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectrometer data by deconvoluting the peaks were carried out for assigning and accurately identifying the peaks associated to a particular PVDF phase. SEM micrographs further helped in understanding the mechanism of desired \b{eta}-phase as well as in obtaining a condition for bead-free nanofibers. Interestingly, the mechanism of formation of phases are found mostly governed by the balance between surface tension and viscosity which is controlled by PVDF concentration and acetone content in the solution. A PVDF concentration of 20% (w/v) and DMF:Acetone ratio 1:1 was found suitable for maximum \b{eta}-phase in a completely bead-free nanofibers. The methodology and understanding of underlying mechanism of desired phase and morphology suggest a guideline for optimization of \b{eta}-phase and bead-free fibers in PVDF-based nanocomposite as well.

cond-mat.mtrl-sci↗

arXiv2021

Performance of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler in PVDF nanocomposite as flexible energy storage and harvester

We demonstrate the potential of dopamine modified 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 filler incorporated poly-vinylidene fluoride (PVDF) composite prepared by solution cast method as both flexible energy storage and harvesting devices. The introduction of dopamine in filler surface functionalization acts as bridging elements between filler and polymer matrix and results in a better filler dispersion and an improved dielectric loss tangent (<0.02) along with dielectric permittivity ranges from 9 to 34 which is favorable for both energy harvesting and storage. Additionally, a significantly low DC conductivity (< 10-9 ohm-1cm-1) for all composites was achieved leading to an improved breakdown strength and charge accumulation capability. Maximum breakdown strength of 134 KV/mm and corresponding energy storage density 0.72 J/cm3 were obtained from the filler content 10 weight%. The improved energy harvesting performance was characterized by obtaining a maximum piezoelectric charge constant (d33) = 78 pC/N, and output voltage (Vout) = 0.84 V along with maximum power density of 3.46 microW/cm3 for the filler content of 10 wt%. Thus, the results show 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3/PVDF composite has the potential for energy storage and harvesting applications simultaneously that can significantly suppress the excess energy loss arises while utilizing different material.

cond-mat.mtrl-sci↗

arXiv2018

Study of domain switching using piezoresponse force microscopy in Ca0.4Sr0.6Bi4Ti4O15 thin film for electromechanical applications

An attempt has been made to synthesize (Ca0.4Sr0.6)Bi4Ti4O15(CSBT) thin film using pulsed laser deposition (PLD) and successfully optimized the deposition conditions. A good quality film with the desired phase is obtained at a substrate temperature of 650 oC based on phase, composition and morphology studies. Highly c-axis oriented films with average thickness 330-400 nm and an average grain size 40-65 nm has been found. Piezoresponse force microscopy (PFM) showed a complete domain reversal using switching spectroscopy. A comparatively high effective d33* value as ~120 pm/V has been achived. The results suggest that CSBT has a great potential in electromechanical applications.

cond-mat.mtrl-sci↗

arXiv2017

Dielectric relaxation and electrical conductivity in lead-free (100-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics: An impedance spectroscopic study

Dielectric behavior and conductivity mechanism in lead-free (100-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics were investigated using impedance spectroscopy over a wide temperature (-100 oC to500 oC) and frequency range (0.1 Hz to1 MHz). The grain and grain boundary response as well as the relaxation processes at different frequencies and temperatures were also discussed. A low frequency dispersion in dielectric permittivity (LFDD), a typical characteristic of high-temperature behavior was observed both below and above the ferro-paraelectric phase transition temperature, Tm. Oxygen-defect-related complexes generated due to acceptor type doping were found to play an important role in LFDD and hopping conduction. The dielectric relaxation follows Jonscher universal law, however LFDD is found to be associated with quasi-DC process (QCD). The activation energies of DC conduction confirm the mechanism as the thermal motion (short range hopping) of doubly ionized oxygen vacancies. At high temperature, the conductivity relaxation mechanism is dominated by grain boundary conduction through hopping electron created by the charge compensating oxygen vacancies.

cond-mat.mtrl-sci↗

arXiv2014

Structure, microstructure and electrical properties of new lead-free (1-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics

A new lead-free (1-x)Li0.12Na0.88NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics have been prepared using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO3 content, x = 10-12.5. A partial phase diagram has been established based on temperature-dependent permittivity data for this new system and a nearly vertical temperature-independent MPB is observed. An improvement in electrical properties near MPB (e.g., for x = 12.5; εr = 10489 at Tm, d33 = 30 pC/N, kp = 12.0 %, Qm = 162, Pr = 11.2 μC/cm2, Ec = 19.2 kV/cm, d*33 = 269 pm/V) is observed and is attributed to the ease of polarization rotation due to coexistence of orthorhombic and tetragonal phases. The results show that these materials could be suitable for piezoelectric vibrators and ultrasonic transducers applications. The sample with x = 25, also shows high dielectric permittivity, εr = 3060, and low dielectric loss, tanδ = 0.033 which could be suitable for capacitor (X7R/Z5U) applications.

cond-mat.mtrl-sci↗

arXiv2014

Composition induced diffused to relaxor ferroelectric phase transition in lead-free (1-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 0.40) ferroelectric ceramics

(1-x)Li0.12Na0.88NbO3-xBaTiO3 (0 to x to 0.40) ferroelectric ceramics were prepared using conventional ceramics route and their phase transitional behavior is investigated by using dielectric spectroscopy. The temperature-dependent dielectric permittivity epsilon'(T) shows a diffused ferroelectric-paraelectric transition for all compositions. An acceptable and competent characterizing parameter (D) of diffused phase transition (DPT), defined by Uchino et al. [J Am Ceram Soc 2010;93:4011], was measured and validated. Interestingly, a crossover from diffused ferroelectric phase transition (FE-DPT) to relaxor ferroelectric (RFE) transition is found for the composition x greater than equal to 0.225. The FE-DPT is characterized by a frequency-independent temperature of dielectric maxima (Tm), while a RFE is found to have frequency-dependent Tm satisfying Vogel-Fulcher relation. The composition induced crossover is attributed to the dynamics of different PNR size and relaxation times that varies with different BaTiO3 content (x) leading to the appearance of a FE-DPT or RFE.

cond-mat.mtrl-sci↗