Physical Properties and Structure of Ferrite Melts

Density, viscosity, electrical conductivity and surface tension have been measured to find out the behavior of Fe^<3+> -ions in the molten Na_2O-Fe_2O_3, RO-Fe_2O_3 (R=Ca, Sr, Ba) systems. In these melts Fe^<3+> -ion may be an amphoteric ion, that is, the oxygen coordination number of Fe^<3+> is 4 and/or 6(Fe^<3+>(4) and/or Fe^<3+>(6). Fe^<3+>(4) forms a complex anion with oxygen such as Si^<4+>, and Fe^<3+>(6) acts as a cation. Effects of Na_2O and RO-content on the physical properties of ferrite melts have been discussed in term of the ratio of Fe^<3+>(4) and Fe^<3+>(6). The controlling factors of Fe^<3+>(4)/Fe^<3+>(6) ratio are the basicity and content of alkali, alkaliearth oxides. The distribution of Fe^<3+>(4) and Fe^<3+>(6) for the RO-Fe_2O_3 systems was assumed by considering the basicity and content of RO, and measured values of physical properties. IR spectra and Mossbauer spectra of splat quenched glassy samples are measured to estimate the structure of molten state and these support this distribution. The magnetic properties of crystallized glasses were measured. The coercive forces depended on the BaO・6Fe_2O_3 particle size and it showed the maximum value of 5.6kOe with the size of 800Å