EXAFS and XANES Study of a Pure and Pd Doped Novel Sn/SnOx Nanomaterial

Abstract

EXAFS and XANES at the Pd and/or Sn K-edge have been used to characterize pure and palladium doped spherical particles (10−63 nm diameter) of a novel Sn/SnOx nanocomposite. This nanomaterial prepared by decomposition of organic precursors has found application in a new type of high performance solid-state gas sensor. Except for the sample annealed at 600 °C that is mainly pure crystalline tetragonal cassiterite SnO2, the undoped nanoparticles consist of a Sn metallic core surrounded by a layer of tin oxide that is mostly amorphous. In this outer layer, tin atoms were found to be 4−5-fold coordinated to oxygen with bond distances slightly larger than in bulk cassiterite SnO2. The average tin oxidation state in the oxide phase was evaluated using the length of the tin−oxygen bond to be between +3.7 and +3.5. The relative ratio of Sn atoms in the metallic phase was estimated between 15 and 36% of the total number of Sn atoms using the coordination number of the first Sn shell corresponding to the tin β tetra...