Crosslinkable aromatic resin having protonic acid group, and ion conductive polymer membrane, binder and fuel cell using the resin.

This multilayer structure is then heated and fired in a single thermal cycle to remove any binder materials and sinter, respectively, the fuel cell.

When the oxygen fuel ratio is too high, particle decarburization and binder phase nonuniform contract in the cooling process are the determining factors to the coating structure and properties.