JOINT IMPEDANCE SPECTROSCOPY ANALYSIS OF 10Sc1CeSZ AND 8YSZ SOLID ELECTROLYTES FOR SOFC

Abstract

Total ionic, grain and grain boundary conductivity of traditional 8YSZ and promising 10Sc1CeSZ electrolytes for solid oxide fuel cells (SOFC) were studied. Samples were sintered at 1400 °С due to best values of the ionic conductivity, as it was shown earlier. The total conductivity of 10Sc1CeSZ electrolytes at 600 °C varied from 0.019 to 0.046 S/cm depending on the initial powder, and for 8YSZ it was 0.059 S/cm. The activation energies were 0.88-1.07 eV and 1.04 eV, respectively. The grain boundary conductivity prevails in YSZ electrolytes due to higher association enthalpy of the grain at temperatures below 560 °C which depends on the dopant size. In 10Sc1CeSZ electrolytes the charge transfer passes mainly through the grains: the main contribution to the grain boundary resistivity is given by SiO₂ segregations at the grain boundaries in technically pure materials; and grain-to-grain contacts in highly pure materials. The grain boundary resistivity drops twice due to presence of Al₂O₃ admixtures known for their scavenging effect on SiO₂ segregations.