The specific conductance of zirconium phosphate decreases considerably with increase in the degree of crystallinity; however the energy of activation for the conduction apparently does not depend on the degree of crystallinity and is surprisingly low (11–13 KJ/mole). In order to explain these results, different samples of Zr(HPO4)2·H2O of the same degree of crystallinity but having different specific surface area were obtained by sedimentation and the amount of surface counter-ions per cm3 of microcrystals and the specific conductance measured. It was found that a large fraction of the total current was transported by the surface counter-ions, their mobility being ⩾104 times that of the internal ones. Thus, the low activation energy for ionic conduction in the crystalline material is due essentially to the transport of surface counter-ions. These results demonstrate that the counter-ions present at the surface of microcrystals of zirconium phosphate make an important contribution to the total conduction, to the activation energy, and to the electrochemical properties of membranes consisting of microcrystals of zirconium phosphate.
On the mechanism of diffusion and ionic transport in crystalline insoluble acid salts of tetravalent metals—I Electrical conductance of zirconium bis (monohydrogen ortho-phosphate) monohydrate with a layered structure
RICCIARDI, Giampaolo
1978-01-01
Abstract
The specific conductance of zirconium phosphate decreases considerably with increase in the degree of crystallinity; however the energy of activation for the conduction apparently does not depend on the degree of crystallinity and is surprisingly low (11–13 KJ/mole). In order to explain these results, different samples of Zr(HPO4)2·H2O of the same degree of crystallinity but having different specific surface area were obtained by sedimentation and the amount of surface counter-ions per cm3 of microcrystals and the specific conductance measured. It was found that a large fraction of the total current was transported by the surface counter-ions, their mobility being ⩾104 times that of the internal ones. Thus, the low activation energy for ionic conduction in the crystalline material is due essentially to the transport of surface counter-ions. These results demonstrate that the counter-ions present at the surface of microcrystals of zirconium phosphate make an important contribution to the total conduction, to the activation energy, and to the electrochemical properties of membranes consisting of microcrystals of zirconium phosphate.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
