GDC20($Ce_{0.8}Gd_{0.2}O_{1.9}$) powder was synthesized from Ce and Gd nitrate solutions using ammonium carbonate($(NH_4)_2CO_3$) as a precipitant. Attrition-milling of the powder, which had been calcined at $700^{circ}C$ for 4 h, decreased an average particle size of 2.2 ${mu}m$ to 0.5 ${mu}m$. The milled powder consisted of nano-sized spherical primary particles. Due to the excellent sinterability of the powder, sintering of the powder compacts for 4 h showed relative densities of 80% at 1000 $^{circ}C$ and 96.5% at $1200^{circ}C$, respectively. Densification was found to almost complete at $1300^{circ}C$, resulting in a dense and homogeneous microstructure with a relative density of 99.5%. The grains of ~0.2 ${mu}m$ in size at $1200^{circ}C$ grew to ~1 ${mu}m$ in size at $1300^{circ}C$ as a result of a rapid grain growth.