Influence of Ti⁴⁺ on the Energetics and Microstructure of SnO₂ Nanoparticles

The effect of an additive in the microstructure of an oxide can be related to changes of both kinetic and thermodynamic parameters. However, Ti and Sn ions have the same charge (⁴⁺), similar ionic radii and both TiO₂ and SnO₂ crystallize in the tetragonal rutile structure, and thus changes in the kinetics parameters are not expected to occur. Nanocrystalline Sn_1-xTi_xO₂ rutile-structured solid solutions have shown promise as gas sensors and photocatalysts. A fuller understanding of their microstructure and thermodynamics is necessary to improve the performance of the device. In this work, Sn_1-xTi_xO₂ (0.00 ≤ x ≤ 0.50) rutile-structured nanoparticles were synthesized by Pechini method at 500 °C for 15 h. Upon increasing the Ti⁴⁺ content, both crystallite size determined by XRD and particle size determined by N₂ adsorption decrease. However, it is suggested that the surface of the nanocrystalline Sn_1-xTi_xO₂ has a similar structure to TiO₂ anatase, which has a lower surface energy compared to both SnO₂ and TiO₂ rutile.