Impedance Analysis of Dielectric Nanoparticles Enabled via a Self‐Assembled Monolayer

Abstract

Impedance spectroscopy has been shown to be a powerful tool to investigate the dielectric characteristics of powders suspended in suitable liquids. The electrical and dielectrical contributions of different components of the slurry can be extracted from the impedance spectra through measurement of frequency‐dependent relaxations. However, for ferroelectric powders that possess innate surface conductivity, such as BaTiO3, nanoparticles have sufficient conductivity to exclude low‐frequency fields that preclude impedance characterization of the particle core. In this work, the slurry technique is shown to be effective for dielectric characterization of not only micrometer‐sized particles through equivalent circuit modeling but also applicable to nanometer size dielectric particles upon remediating the conductive surface defect. Application of a self‐assembled monolayer (SAM) onto the nanoparticle as a surface passivation layer reduces the surface conductivity, stabilizes the nanoparticles to dissolution, and allows a reproducible measurement and modeling of the nanoparticle dielectric characteristics including nanoparticle permittivity. The dielectric permittivity of surface passivated, ~40 nm diameter barium titanate particles was measured to be εr ~ 135.

Interfacial Polarization-Induced Loss Mechanisms in Polypropylene/BaTiO3 Nanocomposite Dielectrics

“…The higher permittivity for the BT NPs could be attributed to a higher ferroelectric content than that in the BT@POSS NPs. The permittivity (123) for the BT@POSS NPs was close to the value (εr ~135) reported for organophosphate surface-passivated 30-50 nm BaTiO3 NPs determined by impedance spectroscopy analysis 54. …”

Impedance spectroscopy studies of surface engineered TiO2 nanoparticles using slurry technique

“…An equivalent circuit approach with two RC elements connected in series was used to extract quantitative information, such as the permittivity of dielectric particles, from the impedance spectra of the slurries as described earlier. 19 Z-view software (Scribner Inc., Southern Pines, NC) was used to fit the spectra with the equivalent circuit model and to calculate the parameters within the equivalent circuit. The accuracy and the limitations of this impedance spectroscopy using the slurry technique have been discussed in the previous investigations.…”

“…The accuracy and the limitations of this impedance spectroscopy using the slurry technique have been discussed in the previous investigations. [12][13][14][15][16][17]19 A selected list from those investigations are: low-frequency characterization technique has better accuracy and reliability for high dielectric contrast mixtures (as in the present study), while other high frequency techniques are preferable for low dielectric contrast mixtures; particle size itself does not influence the impedance spectra, although particle properties are size dependent; it is desirable to have the solids loading higher than 10% for greater particle signal, but which is limited by percolation threshold that influences dispersion quality, including the presence of air voids and particle gravimetric settling; dielectric permittivity characterization is almost constant for different particle volume concentrations; unlike microparticle slurries, nanoparticle slurries are stable and not susceptible to settling and thus does not influence the dielectric characterization results.…”

“…6,[12][13][14][15][16][17][18] *Author for correspondence (siddabattunisasidhar@sssihl.edu.in) While the slurry methodology has been demonstrated for a variety of metal oxide ceramic powders, it was shown to be applicable for micron-sized particles but not for nanoparticles due to the surface conductivity and surface energy effects of the nanoparticles compounded by the large surface area of nanoparticles. 6,19 However, in our earlier works, the particle slurry impedance spectroscopy technique was shown to be effective in characterizing the dielectric permittivity of nano-sized ceramic particles like BaTiO 3 and TiO 2 as well by the application of a self-assembled monolayer (SAM) onto the nanoparticle as a surface passivation layer that mitigates the surface conductivity and the surface energy effects of the nanoparticles. 19,20 Surface treatment of nanoparticles is very crucial in the field of polymer nanocomposites with regard to compatibility and quality of dispersion of inorganic nanoparticles in organic polymer matrices.…”

“…6,19 However, in our earlier works, the particle slurry impedance spectroscopy technique was shown to be effective in characterizing the dielectric permittivity of nano-sized ceramic particles like BaTiO 3 and TiO 2 as well by the application of a self-assembled monolayer (SAM) onto the nanoparticle as a surface passivation layer that mitigates the surface conductivity and the surface energy effects of the nanoparticles. 19,20 Surface treatment of nanoparticles is very crucial in the field of polymer nanocomposites with regard to compatibility and quality of dispersion of inorganic nanoparticles in organic polymer matrices. 5,20 Hence, care should be taken in selecting the appropriate surface modifying agents, suitable for the intended application of polymer nanocomposites.…”