A process for forming an electrolyte for a metal-supported solid-oxide fuel cell, the process comprising: a. combining a doped-ceria powder with a sintering aid and solvent to form a slurry; b. applying the slurry to an anode layer; c. drying to form a green electrolyte; and d. firing the green electrolyte to form a sintered electrolyte; wherein the slurry in step b. comprises doped-ceria powder with a physical property selected from bimodal particle size distribution, a BET surface area in the range 15-40 m2/g, a spherical morphology, or combinations thereof together with an electrolyte obtained by the process, a fuel cell and fuel cell stack, comprising the electrolyte, and the use of the fuel in the generation of electrical energy.