system: Unraveling of microscopic features by Raman spectroscopy

Raman spectroscopic studies were carried out on a complete range of ceria–gadolinia solid solutions ( Ce 1 − x Gd x O 2 − x / 2 ) to determine the intricate microscopic changes that occur in the system. The system is characterized by the presence of an F-type Raman mode until x ≤ 0.2 , the co-existence of Raman modes of both F-type and C-type in the range ( 0.3 ≤ x ≤ 0.8 ) and mostly C-type Raman mode for x ≥ 0.8 . Several broad modes indicating a high degree of disorder in the F-type lattice could also be observed. As the system ( Ce 1 − x Gd x O 2 − x / 2 ) moves from x = 0.0 to x = 1.0 , the average co-ordination number changes from 8 to 6 which brings about interesting changes at the microscopic level. These changes are readily exhibited by the variation in Raman spectra of various consecutive nominal compositions. This investigation establishes the utility of Raman spectroscopy in convincingly ascertaining the existence of C-type domains in an F-type matrix and vice-versa.