Synthesis and characterization of coprecipitation-derived ferrimagnetic glass-ceramic

Ferrimagnetic glass-ceramics could be used for magnetic induction hyperthermia. This technique is utilised for the destruction of solid neoplastic diseases by application of an alternating magnetic field. Biocompatible ferrimagnetic materials could be easily incorporated into a tumour and could generate heat mainly by hysteresis loss. A ferrimagnetic glass-ceramic in the system SiO₂–Na₂O–CaO–P₂O₅–FeO–Fe₂O₃ has been prepared by melting of the coprecipitation-derived raw materials. This glass-ceramic contains a unique crystalline phase, magnetite, embedded in an amorphous matrix. Magnetite crystals precipitate during cooling from melting temperature. This glass-ceramic would no longer require any nucleation and growth thermal treatment, since the maximal quantity of magnetite crystals was produced during cooling. The average unit-cell parameter, crystallite size of magnetite, and the quantitative ratio of the crystallographic phases in the glass-ceramic samples were evaluated using two different methods. Similar results were obtained with both methods. The magnetite crystals are about 50 nm in dimensions. The samples contain 45 wt% of magnetite, homogeneously distributed in the amorphous residual matrix. The as prepared glass-ceramic has a saturation magnetisation of 34 A·m²/kg and a coercive force of 6.7 kA/m. The estimated magnetic loss/cycle under the magnetic field up to 796 kA/m is around 1.45 mJ/g. The specific power loss of this glass-ceramic under a magnetic field of 40 kA/m and a frequency of 440 kHz is 25 W/g. This material showed a bioactive behaviour, as after 2 weeks of soaking in a simulated body fluid the formation of a hydroxylapatite layer on their surface was observed. This feature makes it also suitable for bone cancer.