Abstract
In the present work, 1 mol% alkali metals (Li, Na, K) doped Ce0.9Gd0.1O2-δ (GDC) electrolytes are prepared by citrate-nitrate sol-gel autoignition process. The effects of monovalent alkali metals on the phase structure, micromorphology and grain boundary conductivity of GDC electrolyte are investigated. All Ce0.89Gd0.1A0.01O2-δ (AGDC, A = Li, Na, K) ceramics exhibit a complete fluorite-type structure. SEM results show that all samples sintered at 1400 °C for 5 h have been achieved high densification, and the addition of alkali metals is conducive to the growth of grains. The space charge potential calculated by impedance data has decreased obviously after alkali metals are incorporated into GDC and the value of Ce0.89Gd0.1K0.01O2-δ ceramic is apparently reduced from 0.063 V (GDC) to 0.033 V at 400 °C. These results indicate monovalent alkali metals are beneficial to improve grain boundary conductivity and even total electrical conductivity. Additionally, among all the samples, the Ce0.89Gd0.1K0.01O2-δ electrolyte shows the highest total ionic conductivity of 2.64 × 10−2 S/cm at 700 °C in dry air. The single cell with Ce0.89Gd0.1K0.01O2-δ electrolyte promises the best power density of 624.5 mW cm−2 at working temperature of 700 °C. Therefore, the monovalent alkali metals dopants have promoting effects on improving the grain boundary conductivity, enhancing the sintering activity and output performance of GDC as an electrolyte for IT-SOFCs.
Published Version
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