Nanocrystalline Sn1-xTixO2 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, Sn1-xTixO2 (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. Surface energies and solid-solid interface energies were calculated by combining water adsorption calorimetry and high temperature oxide melt solution calorimetry. Botìi surface energy and solid-solid interface energy decreases with the addition of Ti4+. It is proposed that the stabilization of the particle and the crystallite size are a consequence of the decrease in the surface and interface energies caused by the Ti4+ surface segregation, which is supported by EELS. Given that the surface energy of pure TiO2 rutile reported in the literature is higher than the surface energy of pure SnO2, one may expect that the segregation of Ti4+ in the surface would increase the surface energy contradicting the results. However, it is suggested that the surface of the nanocrystalline Sn1-xTixO2 has a similar structure to TiO2 anatase, which has a lower surface energy compared to both SnO2 and TiO2 rutile.