Electrolyte sheet for solid oxide fuel cell, manufacturing method for electrolyte sheet for solid oxide fuel cell, and single cell for solid oxide fuel cell

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

• a ceramic plate body having a warpage height of not more than 300 μm,
• the ceramic plate body having a shape defined by four sides in clockwise order in a plan view from a thickness direction of the ceramic plate body, the sides including a first side, a second side meeting the first side at a first corner, a third side meeting the second side at a second corner, and a fourth side meeting the third side at a third corner and meeting the first side at a fourth corner,
• wherein in an XY coordinate system of the ceramic plate body in the plan view from the thickness direction with an X axis being a first virtual straight line approximated with 10 points on the first side, a Y axis being a second virtual straight line perpendicular to the first virtual straight line and passing through a point with an X coordinate representing an average of X coordinates of 10 points on the second side, and a virtual origin being an intersection of the first virtual straight line and the second virtual straight line, a third virtual straight line parallel to the first virtual straight line and passing through a point with a Y coordinate representing an average of Y coordinates of 10 points on the third side and a fourth virtual straight line perpendicular to the first virtual straight line and passing through a point with an X coordinate representing an average of X coordinates of 10 points on the fourth side are defined such that a maximum value among values of 100×Q/LX, 100×R/LY, and 100×S/LX is not greater than 1, where Q is a maximum difference between the second side and the second virtual straight line in the X coordinate, R is a maximum difference between the third side and the third virtual straight line in the Y coordinate, S is a maximum difference between the fourth side and the fourth virtual straight line in the X coordinate, LX is a length of a virtual rectangle in an X-axis direction, and LY is a length of the virtual rectangle in a Y-axis direction, the virtual rectangle being defined by the first virtual straight line, the second virtual straight line, the third virtual straight line, and the fourth virtual straight line.