Solid electrolytes for use in lead–bismuth eutectic cooled nuclear reactors

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.