Authors: S Oswald G Behr D Dobler J Werner K Wetzig W Arabczyk
Publish Date: 2003/11/22
Volume: 378, Issue: 2, Pages: 411-415
Abstract
The effect of surface segregation in Sb and Indoped SnO2 finegrained powders has been analyzed in comparison with singlecrystalline samples The kinetics and thermodynamics of the Sb and In segregation processes were studied as a function of annealing temperature by Xray photoelectron spectroscopy XPS after annealing in an oxygencontaining atmosphere Significant differences between diffusion and segregation were revealed for doped powders and single crystals obviously because of simultaneous diffusion and particlegrowth processes proceeding during annealing of powders For doped single crystals the thermodynamic equilibrium is approached after 24 h annealing above 850 °C and at 1000 °C for Sb and In respectively Higher effective activation energies of diffusion are observed for doped powders and the thermodynamic equilibrium is not achieved under technologically relevant annealing conditions On the basis of dopant profile measurements anomalies in the electrical resistivity at 300 °C of Sbdoped SnO2 powders annealed at 700 and 900 °C were attributed to an Sbdepleted zone formed beneath the segregated surface during the kinetic regime To achieve optimum resistivity behavior for commercial application inhomogeneous doping of powders must be avoided by appropriate preparation steps
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