Electrorheological Properties of α-Bi2O3 and Bi2O2CO3

Abstract

Abstract—We have synthesized needle- and platelike α-Bi₂O₃ and Bi₂O₂CO₃ nanoparticles. The bulk density of the α-Bi₂O₃ and Bi₂O₂CO₃ powders is 8.5 and 6.9 g/cm³. The dielectric permittivity of α-Bi₂O₃ and Bi₂O₂CO₃ has been calculated using dielectric permittivity and dielectric loss tangent dispersion measurements in the frequency range from 2.5 × 10¹ to 1 × 10⁶ Hz for 40% suspensions (0.05 and 0.08 volume fractions of α-Bi₂O₃ and Bi₂O₂CO₃, respectively) in PMS-300 polydimethylsiloxane. The value of ε_∞ has been found to be 5.4 for α-Bi₂O₃ and 4.9 for Bi₂O₂CO₃. Dielectric spectra of the suspensions have been shown to exhibit no relaxation behavior in the frequency range studied. We have compared the effects of the shape and dielectric permittivity of the particles on the magnitude of the electrorheological effect in them. Using a simple polarization model, we have analyzed the effect of the dielectric characteristics of the filler material on the yield stress τ₀ of the suspensions in electric fields from 0 to 4 kV/mm. Using a combination of rheometric and direct microscopic observations, we have explained the effect of the type of filler on the electrorheological effect: the Bi₂O₂CO₃-based ERFs have higher shear and compressive yield stresses, whereas the α-Bi₂O₃-based ERFs have a higher tensile yield stress.