Crystal Structure and Lattice Parameter Investigation of La3+ Substituted CeO2 in LaxCe1-xO2-X/2 Synthesized by Solid-State Method

Lanthanum (La) doped Ceria (CeO2) has attracted considerable interest as a candidate material for thermal barrier coating (TBC) because of its low thermal conductivity and potential capability to be operated above 1250°C. In this study, La2Ce2O7 powder was synthesized through the ball mill method. The crystal structure of La3+ substituted CeO2 solid solution was investigated by X-ray diffraction in LaxCe1-xO2-x/2 (0<x< 0.5). The fluorite structure of CeO2 did not change although La3+ was the largest trivalent rare-earth ion. The lattice parameter changed from 5.41 to 5.59Å by increasing La content. Changes in the lattice parameters of LaxCe1-xO2-x/2 that were compared with the theoretical values measured by XRD were obtained based on the oxygen vacancy model. The theoretical lattice parameters were larger than the lattice parameters calculated from the X-ray diffraction pattern. Moreover, the Williamson–Hall equation was used to measure the crystallite size and strain in the LaxCe1-xO2-x/2 lattice as a function of the lanthanum content. The results showed that the presence of lanthanum in the structure reduced the crystallite size.