Disclosed is metal composite oxides having the new crystal structure. Also
disclosed are ionic conductors including the metal composite oxides and
electrochemical devices comprising the ionic conductors. The metal
composite oxides have an ion channel formed for easy movement of ions due
to crystallographic specificity resulting from the ordering of metal ion
sites and metal ion defects within the unit cell. Therefore, the metal
composite oxides according to the present invention are useful in an
electrochemical device requiring an ionic conductor or ionic
conductivity.