The red-ox treatments influence on the structure and properties of M2O3-CeO2-ZrO2 (M = Y, La) solid solutions

The introduction of trivalent cation - Y3+ or La3+ - into the lattice of CeO2-ZrO2 solid solutions allows to stabilise a cubic structure at low ceria content (30 mol%). The reducibility of the samples has been compared in the experiments of temperature-programmed reduction (TPR). Thr introduction of lanthanum cations decreases the amount of hydrogen consumed during TPR, while the introduction of yttrium ones increases this value. At the same time, the value of temperature of the maximum speed of reduction (T-max) is independent on the trivalent dopant. The reducibility of these solid solutions did not change during repeated red-ox treatments at temperature below 1220 K. It is connected with the high thermostability of all systems in this temperature interval. TPR up to 1470 K causes a significant shift of T-max value to higher temperature and a slight decrease of hydrogen consumption in two to three cycles. It is suggested that this alterations are connected with the sharp decrease of the specific surface area of all samples and partially phase decomposition of CeO2-ZrO2 and Y2O3-CeO2-ZrO2 solid solutions. Raman characterisation of the oxygen sublattice of the fresh samples and of the samples after TPR has been carried out. (C) 2001 Elsevier Science B.V. All rights reserved.