Stable sols of 60 nm colloidal zirconia have been prepared by thermolysis of zirconium acetate. The surface complexing acetate groups have been replaced by phosphoric acid groups. Phosphate grafting has been characterized by dynamic light scattering, infrared spectroscopy, 31P nuclear magnetic resonance and impedance spectroscopy measurements. These systems give acid and proton conductive particles (4.10-5 S.cm-1 at 70 % relative humidity).
H3PO4/ZrO2/PVDF-co-HFP composite membranes have been synthesized. Impedance spectroscopy measurements allow discrimination between proton conduction at the surface of the phosphated particles and within free H3PO4 in the polymer. For the highest H3PO4/ZrO2 ratios, the latter phenomenon prevails, giving a proton conductivity of 6.10-4 S.cm-1 at 70 % R.H.