Zinc oxide is widely used in semiconductors fabrication, pigments and mainly in varistors. The electrical properties of ZnO based varistors are related to the grain boundary characteristics, and it can be modified using additives. In this work, zinc oxide based powders were prepared by chemical route derived from the Pechini’s method, and small amounts of tin ions were added to the system. The XRD measurements showed that the tin oxide not forming solid solution in the bulk, and it was observed that the increasing of tin concentration causes an increasing of the surface area at isothermal conditions of calcination. Once the isoelectric point was dislocated to more acid values, the hypothesis of segregation onto surface was considered.