Stability of CsH sub(5)(PO sub(4)) sub(2)-based composites at fixed temperatures and during heating-cooling cycles for solid-state intermediate temperature fuel cells

This work reports the stability of CsH sub(5)(PO sub(4)) sub(2)-based composites at fixed temperatures (158 degree C and 210 degree C) and during three heating-cooling cycles (106 degree C arrow right 158 degree C arrow right 106 degree C). Composites of CsH sub(5)(PO sub(4)) sub(2) and SiO sub(2) prepared by pressing the corresponding powders were stable at fixed temperatures, but were not stable during repeated heating and cooling due to the structural damage or existence of CsH sub(5)(PO sub(4)) sub(2) particles that were not highly dispersed in the silica matrix. Composites of CsH sub(5)(PO sub(4)) sub(2) and SiP sub(2)O sub(7) absorbed a large amount of water into the electrolyte inner phase and formed a paste. The absorbed water had a significant influence on the electrolyte conductivity. Doped glasses of CsH sub(5)(PO sub(4)) sub(2), which had an interconnected silica matrix with 5-12 nm pores filled with CsH sub(5)(PO sub(4)) sub(2), exhibited stable conductivity both at fixed temperatures and during three heating-cooling cycles. From these findings, it was concluded that matrices with both strong interfacial interaction with CsH sub(5)(PO sub(4)) sub(2) and interconnected structure were important to the preparation of CsH sub(5)(PO sub(4)) sub(2)-based composites with high stability.