An attempt was made to prepare proton conductors which were based upon ammonium polyphosphate. The base material was itself almost an insulator, but it became appreciably proton-conducting upon thermally decomposing NH4PO3 into HPO3. The NH4PO3-HPO3 mixture which was thereby obtained exhibited a maximum conductivity of 0.005S/cm at 300C; but also tended to melt at that temperature. In order to increase the melting point, (NH4)2SiP4O13 and Al(PO3)3 were added. The resultant materials remained solid at 400C, and had a conductivity of 0.1S/cm at that temperature. At higher temperatures, the conductivity decreased with increasing temperature. This was due to dehydration, which resulted in the loss of protons.

T.Kenjo, Y.Ogawa: Solid State Ionics, 1995, 76[1-2], 29-34