Effect of Annealing Temperature on the Structural and Magnetic Properties of Co-Doped TiO₂ Nanoparticles via Complex-Polymer Sol–Gel Method

Co-doped TiO₂ nanoparticles were synthesized via non hydrous complex-polymer sol–gel method. A series of Co _x :Ti_1−x O₂ samples with x = 0.01, 0.03, 0.05, 0.08 and 0.10, were prepared and subsequently annealed at 400°, 600° and 800 °C. Structural and magnetic properties of Co _x :Ti_1−x O₂ have been studied by means of X-ray diffraction and DC magnetometry. All samples annealed at 400 °C show a paramagnetic behavior with an average grain size of 11 nm. With increasing annealing temperatures a complete crystallization is seen with growth of the cluster size up to 31 nm with clear evidence of a presence of CoTiO₃. For all concentrations and annealing conditions no sign of a metallic phase, even at x = 0.10, is seen.