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 includes 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, ceramic grains in each of the nine portions have a median size Dof 1.0 μm to 4.0 μm, and a maximum median size Dof the ceramic grains among the nine portions is 1.0 to 1.3 times a minimum median size Dof the ceramic grains among the nine portions.