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