Effect of precursor powder uniformity on structure and electrical properties of gadolinium-doped cerium oxide ceramics

The effects of precursor powder uniformity on structure and electrical properties of Gd-doped CeO2 (GDC) electrolytes were studied. The as-synthesized GDCx powders (x = 5, 10 and 15 at.%) were calcined at 600 and 1200°C and combined in mass ratios of 100:0 and 95:5 to obtain two precursor powders with different particle size distributions. Sintering of the pressed pellets was performed at 1300 and 1400°C for 10 h. Crystal structure, microstructure and electrical properties of the samples were investigated by X-ray diffraction, scanning electron microscopy and AC impedance spectroscopy, respectively. When a smaller proportion of large particles (calcined at 1200 °C) were present in the precursor powders, sinterability of the prepared samples is slowed down, which had an adverse effect on electrical conductivity. The lower the concentration of Gd, the more significant is the adverse effect. At higher sintering temperature (1400°C), the influence of Gd concentration on microstructure and ionic conductivity is more obvious. The GDC15 sample, prepared from the precursor powder calcined at 600°C, had the highest conductivity and σasGB/σBulk ratio at 300°C.