PROTONIC CONDUCTIVITY OF LAYERED ZIRCONIUM PHOSPHONATES CONTAINING-SO3H GROUPS .2. AC CONDUCTIVITY OF ZIRCONIUM ALKYL SULFOPHENYL PHOSPHONATES IN THE RANGE 100-200-DEGREES-C, IN THE PRESENCE OR ABSENCE OF WATER-VAPOR

Two zirconium alkyl-sulphophenyl phosphonates with a-layered structure were prepared and characterized by TG, XRD and impedance measurements. Their formulas are: Zr(O3PC6H4SO3H)0.85(O3PC2H5)1.15.3.7H2O, with interlayer distance 18.5 angstrom, and Zr(O3PC6H4SO3H)0.97 (O3PCH2OH) 1.03.4.9H2O, with interlayer distance 19.6 angstrom. In both cases the crystallization water is completely lost at temperatures lower than 140-degrees-C and the decomposition of the organic moieties starts above 200-degrees-C. Reproducible conductivity values were found for anhydrous zirconium ethyl-sulphophenyl phosphonate in the range 100-180-degrees-C (sigma almost-equal-to 10(-5) S cm-1 at 180-degrees-C in dry N2 with an activation energy of 15.2 kcal/mol). A continuous conductivity decrease was instead observed in this temperature range for zirconium hydroxymethyl-sulphophenyl phosphonate. The conductivity of both compounds is greatly enhanced by the presence of water vapour. Measurements were carried out at 100 and 140-degrees-C; the highest conductivity (sigma almost-equal-to 10(-2) S cm-1) was found for Zr hydroxymethyl phosphonate at 100-degrees-C and 60% relative humidity.