Study on phase relations, crystal structure and magnetic properties of Ti1－xCrxO2±δ system

A series of samples of Ti1-xCrxO2±δ were prepared by Sol-Gel process. The particle size, morphology, valence, solid solution range, phase relations and magnetic properties of Ti1-xCrxO2±δ samples were studied by XRD, SEM, XPS and SQUID measurements. Meanwhile, the Rietveld refinement method was employed to study the effect of Cr doping on the crystal structure ofTiO2. The results show that the solid solution range of both Ti1-xCrxO2±δ systems annealed at 1000℃ are x＝0—0.03. Their lattice parameters decrease with increasing Cr concentration. The results of both XRD analysis and magnetic measurements show that the solid solution range of both Ti1-xCrxO2±δ systems annealed at 1000℃ are x＝0—0.02. Cr ions of samples sintered at 500℃ and 1000℃ have two chemical states, Cr+3 and Cr+6， respectively, while the samples sintered at 1000℃ have much greater Cr+6 content than the ones at 500℃. According to the results of M-H and M-T measurements, magnetic properties of Ti1-xCrxO2±δ samples sintered at 500 ℃ with x=0—0.02 are ferromagnetic. When x≥0.04, they consisted of both ferromagnetic phase and paramagnetic phase. They have stronger ferromagnetic properties at low temperature (50K). The paramagnetic phase is the main constituent and the ferromagnetic phase has less volume fraction at room temperature.