Electrical and microstructural characteristics of GDC electrolyte synthesised by benzoate coprecipitation for solid oxide fuel cells

Gadolinium-doped ceria (GDC) is a promising electrolyte material for developing solid oxide fuel cells (SOFCs) because it offers a higher ionic conductivity at the intermediate operating temperature. In this work, nanocrystalline GDC (Ce1-xGdxO2-x/2, where x = 0.1 and 0.2) powders were synthesised through a novel co-precipitation synthesis method (benzoate route) using ammonium benzoate as a low-cost precipitant. The effect of the synthesis route and processing variables (calcination temperatures and time) on the microstructural and electrical properties of the resulting GDC powder was studied systematically. Multiple GDC electrolyte pellets were fabricated by pressing the GDC powders, followed by sintering the samples at 1100 °C for 6 h. The ionic and electronic conductivity of the GDC pellets were measured in air using EIS at different temperatures (450–750 °C). Huggins' model was used to determine the ionic and electronic conductivity of the GDC pellets. The fabricated electrolyte pellets showed a high relative density of 98.31and 99.02 % for the pre-calcined non-washed and pre-calcined washed powders, respectively, with a crystal size lower than 12 nm. Among all samples, the GDC electrolyte pellet fabricated using the pre-calcined washed powder exhibited the highest ionic conductivity of 3.63E-01 S cm−1 at 750 °C and activation energy of 0.52 eV with an average crystal size of 7–8 nm. The results of this study help to understand and design more efficient ceramic fuel cells with controlled microstructure and compositions at a lower cost.