skip to main content
Explore Scholarly Publications and Datasets in the NSF-PAR

Title: Enhanced Dielectric Permittivity of Optimized Surface Modified of Barium Titanate Nanocomposites
High permittivity polymer-ceramic nanocomposite dielectric films take advantage of the ease of flexibility in processing of polymers and the functionality of electroactive ceramic fillers. Hence, films like these may be applied to embedded energy storage devices for printed circuit electrical boards. However, the incompatibility of the hydrophilic ceramic filler and hydrophobic epoxy limit the filler concentration and therefore, dielectric permittivity of these materials. Traditionally, surfactants and core-shell processing of ceramic fillers are used to achieve electrostatic and steric stabilization for adequate ceramic particle distribution but, questions regarding these processes still remain. The purpose of this work is to understand the role of surfactant concentration ceramic particle surface morphology, and composite dielectric permittivity and conductivity. A comprehensive study of barium titanate-based epoxy nanocomposites was performed. Ethanol and 3-glycidyloxypropyltrimethoxysilan surface treatments were performed, where the best reduction in particle agglomeration, highest value of permittivity and the lowest value of loss were observed. The results demonstrate that optimization of coupling agent may lead to superior permittivity values and diminished losses that are ~2–3 times that of composites with non-optimized and traditional surfactant treatments.
Authors:
; ;
Award ID(s):
1263250
Publication Date:
NSF-PAR ID:
10301010
Journal Name:
Polymers
Volume:
12
Issue:
4
Page Range or eLocation-ID:
827
ISSN:
2073-4360
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , Polymers)
    Polymer-ceramic nanocomposite piezoelectric and dielectric films are of interest because of their possible application to advanced embedded energy storage devices for printed wired electrical boards. The incompatibility of the two constituent materials; hydrophilic ceramic filler, and hydrophobic epoxy limit the filler concentration, and thus, their piezoelectric properties. This work aims to understand the role of surfactant concentration in establishing meaningful interfacial layers between the epoxy and ceramic filler particles by observing particle surface morphology, piezoelectric strain coefficients, and resistivity spectra. A comprehensive study of nanocomposites, comprising non-treated and surface treated barium titanate (BTO), embedded within an epoxy matrix, was performed. The surface treatments were performed with two types of coupling agents: Ethanol and 3-glycidyloxypropyltrimethoxysilan. The observations of particle agglomeration, piezoelectric strain coefficients, and resistivity were compared, where the most ideal properties were found for concentrations of 0.02 and 0.025. This work demonstrates that the interfacial core-shell processing layer concentration influences the macroscopic properties of nanocomposites, and the opportunities for tuning interfacial layers for desirable characteristics of specific applications.
  2. ; ; ; ; ; ; ( , Journal of Materials Chemistry C)
    The effects of growth conditions on the chemistry, structure, electrical leakage, dielectric response, and ferroelectric behavior of Ba 1−x TiO y thin films are explored. Although single-phase, coherently-strained films are produced in all cases, small variations in the laser fluence during pulsed-laser deposition growth result in films with chemistries ranging from BaTiO 3 to Ba 0.93 TiO 2.87 . As the laser fluence increases, the films become more barium deficient and the out-of-plane lattice parameter expands (as much as 5.4% beyond the expected value for Ba 0.93 TiO 2.87 films). Stoichiometric BaTiO 3 films are found to be three orders of magnitude more conducting than Ba 0.93 TiO 2.87 films and the barium-deficient films exhibit smaller low-field permittivity, lower loss tangents, and higher dielectric maximum temperatures. Although large polarization is observed in all cases, large built-in potentials (shifted loops) and hysteresis-loop pinching are present in barium-deficient films – suggesting the presence of defect dipoles. The effects of these defect dipoles on ferroelectric hysteresis are studied using first-order reversal curves. Temperature-dependent current–voltage and deep-level transient spectroscopy studies reveal at least two defect states, which grow in concentration with increasing deficiency of both barium and oxygen, at ∼0.4 eV and ∼1.2 eVmore »above the valence band edge, which are attributed to defect–dipole complexes and defect states, respectively. The defect states can also be removed via ex post facto processing. Such work to understand and control defects in this important material could provide a pathway to enable better control over its properties and highlight new avenues to manipulate functions in these complex materials.« less
  3. ; ; ; ; ; ( , Materials Research Express)
    Abstract

    We report on structural, microstructural, spectroscopic, dielectric, electrical, ferroelectric, ferromagnetic, and magnetodielectric coupling studies of BiFeO3–GdMnO3[(BFO)1–x–(GMO)x], wherexis the concentration of GdMnO3(x= 0.0, 0.025, 0.05, 0.075, 0.1, 0.15, and 0.2), nanocrystalline ceramic solid solutions by auto-combustion method. The analysis of structural property by Rietveld refinement shows the existence of morphotropic phase boundary (MPB) atx= 0.10, which is in agreement with the Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) studies. The average crystallite size obtained from the transmission electron microscopy (TEM) and x-ray line profile analysis was found to be 20–30 nm. The scanning electron micrographs show the uniform distribution of grains throughout the surface of the sample. The dielectric dispersion behavior fits very well with the Maxwell-Wagner model. The frequency dependent phase angle (θ) study shows the resistive nature of solid solutions at low frequency, whereas it shows capacitive behavior at higher frequencies. The temperature variation of dielectric permittivity shows dielectric anomaly at the magnetic phase transition temperature and shifting of the phase transition towards the lower temperature with increasing GMO concentration. The Nyquist plot showed the conduction mechanism is mostly dominated by grains and grain boundary resistances. The ac conductivity of all the samples follows the modifiedmore »Jonscher model. The impedance and modulus spectroscopy show a non-Debye type relaxation mechanism which can be modeled using a constant phase element (CPE) in the equivalent circuit. The solid-solutions of BFO-GMO show enhanced ferromagnetic-like behavior at room temperature. The ferroelectric polarization measurement shows lossy ferroelectric behavior. The frequency dependent magnetocapacitance and magnetoimpedance clearly show the existence of intrinsic magnetodielectric coupling. The (BFO)1–x–(GMO)xsolid solutions withx= 0.025–0.075 show significantly higher magnetocapacitance and magnetoimpedance compared to the pure BFO.

    « less
  4. ; ; ; ; ; ( , IEEE International Conference on Soft Robotics (RoboSoft))
    Soft, stretchable sensors, such as artificial skins or tactile sensors, are attractive for numerous soft robotic applications due to the low material compliance. Conductive polymers are a necessary component of many soft sensors, and this work presents the electromechanical characterization of 3D-printable conductive polymer composites. Dog-bone shaped samples were 3D printed using a digital light processing (DLP)-based 3D printer for characterization. The 3D printable resin consists of monomer, crosslinker, conductive nano-filler, and a photo-initiator. The characterization was performed in two tracks. First, the effect of two different crosslinkers was investigated with different compositions and second, the effect of concentration of conductive nano-fillers was explored. Crosslinkers were chosen by referring to previous studies, and carbon nanotubes (CNTs) were utilized as conductive nano-fillers. The samples were 3D printed and characterized using an electromechanical test setup. To demonstrate utility for 3D printed soft robotics, a capacitance-based joystick sensor composed of both conductive and non-conductive resins was 3D printed.
  5. ; ; ; ( , Micromachines)
    Due to their favorable electromechanical properties, such as high sound velocity, low dielectric permittivity and high electromechanical coupling, Aluminum Nitride (AlN) and Aluminum Scandium Nitride (Al1−xScxN) thin films have achieved widespread application in radio frequency (RF) acoustic devices. The resistance to etching at high scandium alloying, however, has inhibited the realization of devices able to exploit the highest electromechanical coupling coefficients. In this work, we investigated the vertical and lateral etch rates of sputtered AlN and Al1−xScxN with Sc concentration x ranging from 0 to 0.42 in aqueous potassium hydroxide (KOH). Etch rates and the sidewall angles were reported at different temperatures and KOH concentrations. We found that the trends of the etch rate were unanimous: while the vertical etch rate decreases with increasing Sc alloying, the lateral etch rate exhibits a V-shaped transition with a minimum etch rate at x = 0.125. By performing an etch on an 800 nm thick Al0.875Sc0.125N film with 10 wt% KOH at 65 °C for 20 min, a vertical sidewall was formed by exploiting the ratio of the 1011¯ planes and 11¯00 planes etch rates. This method does not require preliminary processing and is potentially beneficial for the fabrication of lamb wave resonatorsmore »(LWRs) or other microelectromechanical systems (MEMS) structures, laser mirrors and Ultraviolet Light-Emitting Diodes (UV-LEDs). It was demonstrated that the sidewall angle tracks the trajectory that follows the 1¯212¯ of the hexagonal crystal structure when different c/a ratios were considered for elevated Sc alloying levels, which may be used as a convenient tool for structure/composition analysis.« less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email