Ytterbium oxide from different precursors: formation and characterization - Thermoanalytical studies

Thermal processes involved in the decomposition course of hydrated ytterbiu m acetate (Yb(CH3COO)(3). 4H(2)O) and oxalate (Yb-2(C2O4)(3). 6H(2)O) up to 900 degrees C, in atmosphere of air, were monitored by non-isothermal grav imetry and differential thermal analyses. The gaseous decomposition product s were identified by gas mass spectroscopy. Intermediates and final solid p roducts were characterized by X-ray and scanning electron microscopy. The r esults showed that Yb-acetate dehydrates in four steps and decomposes to Yb 2O3 at 560 degrees C, through four non-crystalline unstable intermediates. For Yb-oxalate, the dehydration occurs in three steps. The anhydrous oxalat e is thermally unstable and immediately decomposes to Yb2O3 at 600 degrees C through two unstable intermediates. The crystalline oxide obtained from t he acetate contains large pores in comparison to that oxide obtained from o xalate as indicated from SEM results. The volatile decomposition products f rom the acetate are water vapor, acetic acid, ketene, acetone and methane. (C) 1999 Elsevier Science S.A. All rights reserved.