The operating temperature of electrochemical oxygen sensors can likely be lowered by reducing the solid electrolyte resistance. Most often, these sensors use yttria partially stabilized zirconia (e.g. (Y2O3)0.05(ZrO2)0.95, (5-YSZ)) as solid electrolyte. In this paper, we discuss the use of better conducting ceramics than yttria partially stabilized zirconia, as solid electrolytes for oxygen sensors that can be applied in lead-bismuth eutectic (LBE) cooled nuclear reactors. Two stabilized zirconia ceramics ((Y2O3)0.08(ZrO2)0.92, (8-YSZ); (Sc2O3)0.1(CeO2)0.01(ZrO2)0.89) are investigated as well as a hypostoichiometric perovskite-type La0.8Sr0.2Ga0.8Mg0.2O3-d. The results of microstructural analyses, thermochemical stability tests in LBE (at 360 °C), as well as mechanical tests and four-probe d.c. conductivity measurements (at 300 – 800 °C) are discussed and compared with the results that were obtained for a commercially available 5-YSZ (Friatec AG, Germany) . Of the three studied ceramics, 8-YSZ was identified as the most promising solid electrolyte to reduce the operating temperature of electrochemical oxygen sensors.