Solid ion conductor, electrode and solid oxide cell each including the solid ion conductor

A solid ion conductor comprising a first metal oxide having a perovskite structure,

• wherein the first metal oxide comprises a first element, a second element, and a third element, disposed at cuboctahedral sites of the perovskite structure,
• and comprises a fourth element and a fifth element, disposed at octahedral sites of the perovskite structure, or a fourth element, a fifth element, and a sixth element, disposed at octahedral sites of the perovskite structure,
• wherein the first element is an element belonging to Group 3 of the Periodic Table,
• the second element and the third element are each independently an element belonging to Group 2 of the Periodic Table and have an atomic weight of 30 or more,
• the fourth element and the fifth element are each independently an element belonging to one of Groups 8 to 11 of the Periodic Table,
• the sixth element is an element belonging to one of Groups 3, 4, or 7 to 12 of the Periodic Table, and
• wherein formation energy of the first metal oxide is about −0.8 electronvolt to about −10 electronvolt, compared to formation energy of a second metal oxide formed by excluding the first element from the first metal oxide.