Preparation and conductivity measurements of ammonium polyphosphate-based proton conductors

This paper reports the preparation and characterization of the solid solution (NH4)2Si1-xTixP4O13 (0 ≤ x ≤ 1). Structural and transport properties of six members in this series have been investigated with the aim to check the effect of composition on the physical properties of this family of compounds. Moreover, the reversibility of the hydration process, at the basis of the high proton conductivity in humid atmosphere, was monitored. Results show that the effect of composition on the transport properties of this class of materials is negligible, especially when conductivity is measured in humid atmosphere. Partial reversibility of the dehydration process is shown by measuring the conductivity of the sample as a function of time during switching from humid to dry atmosphere.