The electrolyte for SOFCs is a dense ceramic material. It is through this ceramic layer that oxide ions migrate to the anode site, and thus the primary requirement for electrolyte materials is that they should display very good oxide ion conductivity. Yttria stabilised zirconia, ZrO2-Y2O3 (YSZ) is the most common electrolyte material for SOFCs . It has good mechanical properties and is chemically stable over a wide range of operating temperatures and oxygen partial pressures. The material is composed of ZrO2, which is stabilised by Y2O3 or other dopants like MgO and Sc2O3 . The ionic conductivity of this electrolyte material depends on the nature and amount of dopant being used because it is these dopants which create oxygen vacancies in zirconia, which in turn are responsible for oxide ion conduction in the electrolyte .