The impact of sintering and Mg doping on the ionic conductivity of Sm2Zr2O7 pyrochlores

Abstract

Pyrochlore structures based on Sm2Zr2-xMgxO7-x (x = 0, 0.1, 0.15 and 0.2) were synthesized by hydrothermal method at 180 °C and the resulting powders fired at 1200 °C for 2h. Two sintering methods were employed: Conventional Sintering (CS) with uniaxial pressing and Spark Plasma Sintering (SPS), both at 1350 °C. Resulting pellets had relative densities of ∼70 % (CS) and ∼97 % (SPS), with nano-size grains. Electrochemical Impedance Spectroscopy (EIS) was performed under various atmospheres to assess the impact of sintering on electrical properties. All samples exhibit ionic conductivity, with Mg-doped compositions showing the highest conductivity whatever the sintering process used. SPS samples showed higher conductivity than those sintered by CS, with the x = 0.10 composition (SMZ01) exhibiting the highest conductivity. The overall conductivity was unaffected by atmosphere (air, N2 and H2–N2), indicating good stability and resistance to reduction/oxidation. Notably, SMZ01 sintered by SPS exhibits total conductivity comparable to Yttria-Stabilized Zirconia (YSZ), a standard electrolyte in oxide-ion conducting applications. These Mg-doped ceramics, especially when processed by SPS, offer excellent relative density and conductivity, making them promising candidates for use in Solid Oxide Fuel Cells (SOFCs), Solid Oxide Electrolysis Cells (SOECs), gas sensors, and other clean energy technologies requiring thermal and physical stability.