Synthesis, densification and electrical properties of strontium cerate ceramics

摘要

Powders of pure and 5 percent ytterbium substituted strontium cerate (SrCeO_3/SrCe_(0.95)Yb_(0.05)O_(3-delta) were prepared by spray pyrolysis of nitrate salt solutions. The powders were single phase after calcination in nitrogen atmosphere at 1100 deg C (SrCeO_3) and 1200 deg C (SrCe_(0.95)Yb_(0.05)O_(3-delta)). Dense SrCeO_3 and SrCe_(0.95)Yb_(0.05)O_(3-delta) materials were obtained by sintering at 1350-1400 deg C in air. Heat treatment at 850 and 1000 deg C, respectively, was necessary prior to sintering to obtain high density. The dense materials had homogenous microstructures with grain size in the range 6-10 mu m for SrCeO_3 and 1-2 mu m for SrCe_(0.95)Yb_(0.05)O_(3-delta). The electrical conductivity of SrCe_(0.95)Yb_(0.05)O_(3-delta) was in good agreement with reported data, showing mixed ionic-electronic conduction. The ionic contribution was dominated by protons below 1000 deg C and the proton conductivity reached a maximum of approx 0.005 S/cm above 900 deg C. In oxidizing atmosphere the p-type electronic conduction was dominating above approx 700 deg C, while the contribution from n-type electronic conduction only was significant above approx 1000 deg C in reducing atmosphere.