A high proton-conductivity was observed in the composite of amorphous phosphate and polytetafluoroethylene (PTFE). Incorporation of amorphous phosphate into PTFE emulsion caused a large increase of conductivity to about 4×10−2S/cm at 23°C. However, the conductivity decreased with increasing heat-treatment temperature, and the fabricated composite showed very low chemical stability.
As a chemically stable composite, PTFE-based composite was also synthesized from α- or γ-zirconium phosphate crystalline powders dispersed in partially polymerized PTFE particles. By addition of zirconium phosphate powders, the proton conductivity jumped up to 2.2×10−3S/cm from 10−13S/cm of PTFE.