EXAFS STUDY OF THE FLUORITE-TYPE COMPOUNDS IN THE SYSTEM BI2O3-GD2O3

The local structure of the fluorite-type compounds in the system (1-x)Bi2O3·xGd2O3 (0≤x≤0.45) has been studied by EXAFS. The differential XANES spectra near the Bi-L3 edge slightly change with composition, whereas no change was observed in those near the Gd-L3 edge, indicating a slightly different geometry of coordination polyhedra around Bi ions with composition. The Gd-O and Bi-O distances in the fluorite structure measured at room temperature are almost constant with Gd2O3 content in the composition range studied, except slight abrupt decrease of Bi-O distance at about x=0.37. The Bi-O distances at room temperature and 700°C are the same value for the composition x=0.40. The results in this study indicate that the coordination polyhedra of the dopant Gd ions are rather regular than those of Bi ions and introduction of Gd2O3 into Bi2O3 stabilizes the fluorite structure by forming a cluster of Gd polyhedra. © 1990.