XAS characterization of the RuO2-Ta2O5 system local (crystal) structure

The influence of the preparation method on the structural properties of the RuO2-Ta2O5 system was investigated. Both thin films on Ti substrates and powder samples of nominal composition Ti/RuO2-Ta2O5 (Ru:Ta = 100:0, 90:10, 80:20, 30:70, and 0:100 at.%) were prepared through thermal decomposition of polymeric precursors (DPP). The thin films and powder samples were investigated using X-ray absorption spectroscopy (XAS). XANES analyses showed that Ru and Ta are present in the Ru(IV) and Ta(V) oxidation states. EXAFS signals of all the samples were analyzed, to obtain the average bond length (r), coordination number, and the Debye-Waller factor (σ2) for each Ru-O, Ru-Ru, Ta-O nearest-neighbor. The first shell Ru-O distance was found at 1.91-1.92 Å with coordination number of 1.8-2.1, and at 2.01-2.02 Å with coordination number of 3.9-4.1. The Ta-O distance obtained for all the samples and in both modes (transmission and fluorescence) had significantly different values from the theoretical ones. The results revealed that the local structure around both the Ru and Ta sites are similar, and that they consist of distorted M-O6 octahedra (where M = Ru or Ta).