Role of iron addition on structure and electrical and magnetic properties of lithium lead borate glasses

The effect of iron oxide addition on the structure and electrical and magnetic properties of lithium lead borate glasses was studied using IR transmission spectra: optical absorption techniques, electrical conductivity, magnetic susceptibility measurements and differential thermal analysis (DTA). IR transmission spectra showed that the addition of up to 3 mol.% iron oxide to the samples introduced as modifiers at the expense of Pb ions. When the amount of iron oxide is increased to more than 3 mol.%, the iron enters the glass structure as network former with an FeO4 structure. The optical absorption properties of glass samples containing different amounts of iron oxide indicated that the oxidation state and the coordination of the doping ions are octahedral. At high contents of iron oxide, some of the iron ions exist in a tetrahedral form. The electrical conductivities as a function of temperature for glass samples containing different amounts of iron oxide up to 10 mol.% Fe2O3 have similar behaviours, from which we deduced the activation energy for each sample. The investigation of the magnetic susceptibility as a function of Fe2O3 concentration concluded that, for high amounts of iron ions, the iron ions exist in an octahedral coordination rather then in a tetrahedral coordination. DTA showed that the samples containing up to 5 mol.% iron oxide are characterized by one crystallization temperature, while samples containing 10 mol.% iron oxide have two crystallization temperatures.