Ionic conductivity investigation in lanthanum (La) and strontium (Sr) co-doped ceria system

► The system Ce1−x−yLaxSryO2−{x/2+y} has been investigated for the first time. ► In present study, number of oxygen vacancies is kept constant in all composition. ► Composition Ce0.89La0.07Sr0.04O1.925 has maximum conductivity more than highest conductivity reported in SDC and GDC at 600 °C. ► It is much less costly than that of SDC and GDC. ► This makes CL7S4 is a potential candidate as a solid electrolyte for ITSOFCs.