Effect of La doping on microstructure of SnO2 nanopowders prepared by co-precipitation method

A series of La-doped SnO2 nanopowders with various dopant concentrations were prepared by chemical co-precipitation technique, and the nanopowders prepared were characterized by differential scanning calorimeter (DSC), thermo-gravimetric (TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results show that La doping can obviously prevent the growth of nanosized SnO2 crystallites. When the La concentration reaches and surpasses 5 at.%, SnO2 crystallite size reaches a minimum value and remains almost constant. With the increase of La concentration, La tends to dissolve in the bulk phase of SnO2 to form solid solution below 10 at.% addition and then starts to disperse onto the surface of the solid solution as a monolayer above 10 at.%. The effect of La doping on hindering crystallite growth can be attributed to the solute drag and lattice distortion resulting from La dissolving in the bulk phase of SnO2 to form solid solution, rather than the monolayer of La on the surfaces of the SnO2 powders.