Electrolyte sheet for solid oxide fuel battery, production method of electrolyte sheet for solid oxide fuel battery, and single cell for solid oxide fuel battery

An electrolyte sheet for solid oxide fuel cells, the electrolyte sheet comprising:

• a ceramic plate body containing a cubic zirconia sintered material,
• wherein, with the ceramic plate body being defined to have nine portions including an outer peripheral portion and a central portion, the nine portions each being a square of equal size, the outer peripheral portion consisting of eight portions located on a periphery of the ceramic plate body, the central portion consisting of one portion surrounded by the outer peripheral portion, ceramic grains in each of the nine portions have a median size D50 of 1.0 μm to 4.0 μm, and a maximum median size D50 of the ceramic grains among the nine portions is 1.0 to 1.3 times a minimum median size D50 of the ceramic grains among the nine portions, the median size D50 of the ceramic grains being defined as a particle size at 50% in a cumulative particle size distribution curve of the ceramic grains expressed as a cumulative percentage against particle size scale.