Electroacoustic properties of barium sulfate particles coated with a conductive layer of antimony/tin(IV) oxides

The dynamic mobility of barium sulfate particles coated with a conducting layer of antimony/tin oxides has been measured with the technique of electroacoustics. Differences between the dynamic mobility spectra of uncoated barium sulfate suspensions and those of the coated particles are observed and attributed to the presence of the conducting surface layer. The magnitude of the complex mobility of the coated particles decreases monotonically with increasing frequency, just as for a nonconducting particle; however, the magnitudes appear to be independent of electrolyte conductivity. The phase angle behavior is also different from that of a low dielectric particle. The change in the phase angle behavior is most obvious at low suspension conductivities and high frequencies where the phase angles show a much smaller phase lag than at higher conductivities. Reasonable agreement between the experimental dynamic mobility spectra and calculated mobilities was found with O'Brien's theory for the enhanced permittivity of semiconductor particles. The results show that electroacoustics could be used to monitor the deposition of these conductive coatings.