Pristine points of zero charge of gallium and indium oxides

Electrokinetic measurements and potentiometric titrations of indium oxide (commercially available reagent grade powder, washed with NaOH and HNO3 to remove strongly adsorbed species) indicate the pristine point of zero charge to be pH 8.7. The isoelectric point at pH 9 was obtained for gallium oxide prepared in the same way. These values match the pristine point of zero charge of alumina, but they are much higher than the values reported for indium oxide and gallium oxide in the literature. (C) 2001 Academic Press.