AC CONDUCTIVITY OF ALPHA-LAYERED ZIRCONIUM-PHOSPHATE IN THE PRESENCE OF WATER-VAPOR AT 100-200-DEGREES-C

The conductivity of pellets of alpha-zirconium phosphate has been investigated between 100 and 200-degrees-C in a nitrogen atmosphere at different relative humidities. Impedance measurements were carried out as a function of temperature (100-200-degrees-C), at fixed relative humidity (RH = 2%), and as a function of relative humidity (2% less-than-or-equal-to RH less-than-or-equal-to 64%), at constant temperature (100-degrees-C). In both cases the conductivity was greatly enhanced by the presence of water vapour. The difference between the conductivity measured at 2% RH and that measured in dry nitrogen becomes larger with decreasing temperature due to the hydration increase of the material exposed to wet nitrogen. At 100-degrees-C the conductivity increases from 1 X 10(-7) S cm-1 (2% RH) up to 5.5 x 10(-6) S cm-1 (64% RH) mostly as a consequence of an increasing surface hydration. On the other hand, measurements carried out on the same pellet with different bulk hydration, showed that, at 2% relative humidity, there is a significant contribution (almost-equal-to 40%) of bulk water to the overall conductivity.