Preparation and Magnetic Properties of Glass-Ceramics Containing [alpha]-Fe for Hyperthermia

Ferromagnetic glass-ceramics can be expected to be useful as thermoseeds for hyperthermia of cancer, especially cancer located at deep parts of body, since hysteresis loss heating locally occurs at the cancer when they are subjected to an alternating magnetic field. Glass-ceramics containing a large amount of α-Fe fine particles in a CaO-SiO2-based glassy matrix were obtained by heat treatment of Fe2O3-CaO-SiO2 glasses under H2 atmosphere. The α-Fe precipitated above 700°C, and its crystallite size and fraction increased with increasing heat treatment temperature to reach 150nm and 17mol% at 1150°C, respectively. The saturation magnetization of the specimen increased from 9 to 57emu·g-1 with increasing heat treatment temperature from 650 to 1150°C. The coercive force of the specimen increased from 50Oe at 650°C to 237Oe at 750°C, and then decreased with increasing heat treatment temperature. The specimen heat-treated at 700°C showed the maximum heat generation, 3W·g-1, under 300Oe and 100kHz. Thus reratively low heat generation of α-Fe-containing glass-ceramics could increase significantly if a magnetic field as large as 10kOe would be available, due to their large saturation magnetization and/or coercive force.