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 Fe${}_2$O${}_3$ with a transition-metal halide FeCl${}_3$ 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 FeCl${}_3$-free and FeCl${}_3$/Fe${}_2$O${}_3$ samples are devitrified glasses, while the Fe${}_2$O${}_3$-free sample is a pure glass. The ESR spectral analysis showed an increase in Fe${}^{3+}$ at the expense of Fe${}^{2+}$, 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 Fe${}_2$O${}_3$-free sample. The FTIR analysis showed an increase in BO${}_4$:BO${}_3$ ratio, as well as the presence of the structural groups (FeO${}_4$ and FeO${}_6$), where the concentration of FeO${}_6$ increased at the expense of FeO${}_4$. 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 Fe${}_2$O${}_3$ was replaced with FeCl${}_3$. 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 Fe${}_2$O${}_3$ was replaced with FeCl${}_3$.