The surface of the pore-filling membrane was observed by FE-SEM (SU6600, Hitachi High-Tech Corporation) at an acceleration voltage of 15 kV. A cross-section of the ZrP membrane was obtained by slicing it with a Focused Ion Beam (FIB) device (FB2200, Hitachi High-Tech Corporation), and the structure of inorganic particles in the ZrP membrane was observed using TEM (JEM-2200FS, JEOL Ltd.). Furthermore, the distribution of ZrP in the membrane was investigated by TEM-EDS (JED-2300T, JEOL Ltd.).