Single fuel cell, fuel cell module, power generation system, high-temperature steam electrolysis cell and methods for manufacturing the same

A single fuel cell according to the present disclosure includes a power generation section, a power non-generation section which does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover the surface of the power non-generation section, and the gas seal film is configured by a structure formed by firing a material containing MTiO3 (M: alkaline earth metal element) and metal oxide. The structure may include a first structure and a second structure which are different in composition, the first structure may include components derived from MTiO3 in larger amounts than the second structure, the second structure may include a metal element contained in the metal oxide in a larger amount than the first structure, and the area ratio of the second structure in the structure may be not less than 1% and not more than 50%.