Patent ID: 7781045

Claim:
An electrolyte sheet for solid oxide fuel cells comprising a sintered ceramic sheet, wherein surface roughness of the sheet as measured by an optical and laser-based non-contact three-dimensional profile measuring system is 2.0 to 20 μm in Rz and 0.4 to 3.0 μm in Ra on both surfaces of the sheet, and wherein a ratio of Rz of one surface (having a greater Rz) to Rz of the other surface having a smaller Rz of the sheet (Rz ratio) is in a range of 1.0 to 3.0 and a ratio of Rmax to Rz (Rmax/Rz ratio) of at least one surface is in a range of 1.0 to 2.0, and wherein Rz (mean roughness depth), Ra (arithmetical mean roughness value), and Rmax (maximum roughness depth) are roughness parameters as determined according to German Standard “DIN-4768” and are numerical values as measured for each surface of the sheet.