The preparation of ceria-based nanoparticles by the flame spray pyrolysis was investigated to develop a new economical preparation method by gas phase reaction. Ceria, gadolinium doped ceria, and ceria doped $TiO_{2}$ nanoparticles were prepared by the disintegration of primary particles in LPG flame. Droplets were thermally converted to primary particles in high temperature flame and then the primary particles were disintegrated because of gas coming off from the decomposition of the precursor. Primary particles were more easily disintegrated as flame temperature increased. The as-prepared particles were under 20 nm in diameter and had polyhedral shape. They were found to be in good crystallinity without post-treatment.
For preparation of gadolinium doped ceria, the effect of gadolinium doping concentration on magnitude of ion conductivity was investigated. The highest conductivity was found to be $1.01×10^{-2} S cm^{-1}$ at 600$^\circ$C for $Ce_{0.75}Gd_{0.25}O_{1.875}$ which is 30% higher than that of the same composition particle prepared by hydrothermal method.
Photocatalytic activity of ceria doped $TiO_{2}$ nanoparticles is higher than that of pure $TiO_{2}$ in visible light region and UV region.
