Structure and electrical properties of some Fe-doped sodium borate devitrified glasses: self-heating action

This study highlight the effect of the replacement of a transition-metal oxide Fe₂O₃ with a transition-metal halide FeCl₃ on the structural and electrical properties of the iron–sodium borate devitrified glass. The preparation process was performed based on the fast quenching principle. The XRD patterns showed that the FeCl₃-free and FeCl₃/Fe₂O₃ samples are devitrified glasses, while the Fe₂O₃-free sample is a pure glass. The ESR spectral analysis showed an increase in Fe³⁺ at the expense of Fe²⁺, while the TEM and SEM images showed some crystallites suspended and distributed randomly within the amorphous glass network matrices of all samples except for that of the Fe₂O₃-free sample. The FTIR analysis showed an increase in BO₄:BO₃ ratio, as well as the presence of the structural groups (FeO₄ and FeO₆), where the concentration of FeO₆ increased at the expense of FeO₄. The V–I characteristics for the studied samples are similar to those of the P–N junction, in which the forward voltage shifted to a lower value when Fe₂O₃ was replaced with FeCl₃. The electric measurements showed a decrease in the DC conductivity values, while that of time-dependence of temperature varying, at a constant electric power, showed that the self-heating of the studied samples decreased when Fe₂O₃ was replaced with FeCl₃.