Magnetic and Electric Properties of Phase Separated Glass Ceramics in CoO-TiO_2-SiO_2 System Prepared by Melt-Quenching Process

摘要

The developments of high performance magnetic materials are required in various applications such as high sensitive magnetic sensing and hyperthermia in cancer treatment. Recently, Co-doped TiO_2 has been received considerable attention as a candidate for such materials because of their ferromagnetic properties at room temperature. On the other hand, the phase-separated glasses and the derived glass-ceramics having unique micro-nano structure are utilized for various applications. In this study, the phase separated glass-ceramics in CoO-TiO_2-SiO_2 system with Al_2O_3 addition were prepared by melt-quenching process. The as-quenched samples consisted of the TiO_2-rich phase and the SiO_2-rich one which were formed by a nucleation-growth mechanism of phase separation. From the results of XRD measurements, the samples were found to have a TiO_2 crystalline phase and a SiO_2-rich glassy phase. The samples showed the magnetic property, which were regarded as a mixture of ferromagnetic and paramagnetic phases. The samples also showed the electric conductivity at room temperature. However, the conductivity of the sample decreased with increase of the Co content, and the temperature dependence of the conductivity of the ferromagnetic samples was different from the other ones. As a result, the Co ions in the phase-separated glass-ceramics in TiO_2-SiO_2 system were found to affect on both the magnetic and the electric conductive characteristics.