Structure and redox properties of Ce_xSn_1-xO₂ mixed oxides

Abstract

A variety of Ce_xSn_1-xO₂ mixed oxides has been synthesized and their structure and redox properties have been studied. The structure of Ce_xSn_1-xO₂ mixed oxides depends on values of 'x' and calcination temperature. When x=l.0~0.8, Ce_xSn_1-xO₂ mixed oxides are in cubic phase; on decreasing x from 0.7 to 0.1, Ce_xSn_1-xO₂ mixed oxides are observed to have cubic and

tetragonal mixed phases; and single SnO₂ is in a tetragonal phase. Only small amounts of SnO₂ can be introduced into the CeO₂ lattice to form cubic phase, and excess SnO₂ is in tetragonal phase. Low calcination temperatures favour formation of Ce_0.7Sn_0.3O₂ solid solutions, while high calcination temperatures do not favour formation of solid solutions and lead to sample sinters. Combined with DTA result, we believe the Ce_0.7Sn_0.3O₂ mixed oxides are formed during the decomposition of the dried sample at about 300 oc. The mixed oxides have three reduction peaks (α, β and γ). The peak α is attributed to the reduction of the easily reducible surface Sn⁴⁺ The peak β is attributed to the overlapping peak of the reduction of bulk oxygen of SnO₂ and the easily reducible surface Ce⁴⁺. The peak γ is ascribed to the reduction of bulk CeO₂. The intensity and temperature of reduction peaks are affected by x values and calcination temperatures.