Sintering and electrical behavior of ZrP2O7–CeP2O7 solid solutions Zr1-xCexP2O7; x = 0–0.2 and (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1 for application as electrolyte in intermediate temperature fuel cells

ZrP2O7-CeP2O7 solid solutions, Zr1-xCexP2O7; x = 0–0.2 and (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1, were prepared by partially replacing Zr4+ with Ce4+ and its effect on the phase composition, sintering behavior, microstructure, and ionic conductivity is analyzed. Ce4+-doped specimens showed improved sintering behavior due to the partial reduction of Ce4+ to Ce3+, as confirmed by X-ray photoelectron spectroscopy (XPS). In unhumidified atmosphere, the electrical conductivity of Zr1-xCexP2O7 increased with increasing cerium content, which can be attributed to the increase in densification and formation of oxygen vacancies due to the partial reduction of Ce4+ to Ce3+. For (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1 specimens, the electrical conductivity increased ≥ 4 orders of magnitude during humidification in air (pH2O = 0.12 atm). At 80 °C, specimen (Zr0.92Y0.08)0.9Ce0.1P2O7 (ZYCP10) showed a maximum of 1.72 × 10−2 S cm−1 which decreased sharply at 100 °C. Furthermore, Zr0.92Y0.08P2O7 (ZYP), (Zr0.92Y0.08)0.95Ce0.05P2O7 (ZYCP5), and ZYCP10 specimens humidified at 160 °C showed the maximum conductivity of 1.04 × 10−3, 1.32 × 10−3, and 8.09 × 10−3 S cm−1, respectively, at 190 °C.