Cost effective Ce1−x−ySrxGdyO2−δ ceramics are developed and compared with Ce0.85Gd0.15O2−δ, in terms of their electrical properties. The amount of expensive Gd3+ is aimed to reduce by co-doping of low cost 2.5-5 mol% Sr2+. Powder x-ray diffraction confirmed the single fluorite structure (space group Fm-3 m) in all the prepared samples. The vital essence of the present study is that a slight Sr2+ co-doping allowed us to reduce a significant Gd3+ doping amount, with a gain in ionic conductivity, compared to Ce0.85Gd0.15O2−δ. For instance, Ce0.875Sr0.025Gd0.10O2−δ solid solution displayed the ionic conductivity, higher than Ce0.85Gd0.15O2−δ with 5 mol% low Gd3+amount. The total electrical conductivities were found to be almost 1 000-10 000 times higher than electronic conductivity at air p(O2) i.e. 0.21 bar, confirming the dominating ionic conduction. However, at extremely low p(O2), the samples show a mixed-ionic electronic conduction (MIEC) behaviour due to Ce4+ to Ce3+ reduction.