Patent ID: 7601447

Claim:
An electrolyte-electrode assembly comprising an electrolyte interposed between an anode and a cathode, wherein said electrolyte is composed of an apatite type oxide which contains a trivalent element and a tetravalent element, which has a composition formula represented by A x B 6 O 12+1.5x provided that A shows said trivalent element, B shows said tetravalent element 8≦x≦10, which has crystals belonging to a hexagonal system, and which provides migration of an oxide ion along a c-axis direction in said crystals thereof when a single crystal is oriented to the c-axis direction so that oxide ion conductivity in the c-axis is higher than oxide ion conductivity in another plane or direction, whereby oxide ion conduction exhibits anisotropy; wherein said electrolyte is a single crystal in which the crystal is oriented in said plane or said direction of said migration of said oxide ion, and said anode and said cathode are arranged perpendicular to a plane or a direction in which said oxide ion conduction of said electrolyte is high; and an isotropic conductive layer, in which said oxide ion conduction exhibits isotropy, is provided between said electrolyte and at least one of said anode and said cathode.