الفهرس 
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Abstract
Purpose of the research : study the effect of Bi2O3 content on the B2O3 matrix, How glass properties are controlled by Fe2O3 and/or Bi2O3 content in Fe2O3-Bi2O3-B2O3 glass system. Materials and methods used : The studied glasses were prepared by using high purity reagent grade H3BO3, (Fe2O3 lll) and (BiO)2CO3H2O as initial material. The well-mixed components were added in small portions and melted using porcelain crucibles in an electric furnace at a temperature ranging between 800 and 1250 °C, depending on the glass composition. The crucible and its content was kept in the furnace about 20-30 min. The melt was swirled frequently to ensure the homogeneity and to get rid of air bubbles before being quenched to room temperature by pressing it between iron plates. Due to tendency of some compositions to absorb moisture at the long run, the glass samples were sealed with silica jell granules in plastic sacks and kept in desiccators until required. Summary and Conclusions : In the present study the role of Bi2O3 and Fe2O3 in the structure and the physical properties of Fe2O3-Bi2O3- B2O3 glasses has been investigated in a wide range of compositions. FTIR analysis has been used to follow the structural changes that take place with changing the concentration of the constituents. In x Bi2O3·(100-x) B2O3 glasses N4 continuously increases with increasing Bi2O3 content up to ” " ~ " ” 45 mol% Bi2O3. Beyond this concentration N4 values decrease. This indicates that Bi2O3 modifies the borate matrix by changing BO3 symmetric units into BO4 units up to ” " ~ " ” 45 mol% then BO3 asymmetric units formed at the expense of BO4 units. There is a linear increase in density (D) accompanied with a linear increase in molar volume (Vm) with increase the Bi2O3 content. N4 values obtained from the IR spectra can be used to calculate the densities and molar volumes for the different structural units of the glass by using Doweidar’s model. For all the studied glasses, it is found a good agreement, in trend and values, between experimental and calculated density and molar volume which supports the expected view about the glass structure. X-ray diffraction (XRD) patterns of x Bi2O3·(100-x) B2O3 system (30 ≤ x ≤ 65 mol%) showed no sharp peaks, only broad diffraction humps that confirms a short range order characteristics of amorphous glassy phase. TEM measurements affirm the presence of some small phases with different sizes formed of clusters. In addition, the results indicate that electron diffraction patterns (EDP) is more sensitive than XRD in detecting phases at low degree of crystallinity and the ability for crystallization. Whereas, scanning electron micrographs (SEM) show agglomerates of phases separated from the amorphous matrix. This agglomerate increases with increasing Bi2O3 content. According to FTIR analysis, X-ray diffraction (XRD) patterns, TEM and SEM measurements it can be concluded that Bi3+ ions prefer to form its own matrix rather than modifying the borate matrix particularly at higher concentrations, which confirms that Bi2O3 can act as a glass modifier and former in Bi2O3-B2O3 glass system. All the studied glasses show a linear dependence of the logarithm of conductivity (log) on the reciprocal of absolute temperature (1/T) which is a characteristic feature of the ionic conduction process that can be described by Arrhenius relation. It is observed that log523 linearly increases while E seem to be constant with increasing Bi2O3 content. it is concluded that the conductivity of the glasses is mobility-independent and mainly controlled with o. For both ternary glass series, XRD patterns exhibit sharp peaks corresponding to -Fe2O3 crystalline phase for high content of Fe2O3 and the degree of crystallinity increases with increasing Fe2O3 content. FTIR analyses indicate that the majority of BO4 units modified by Bi3+ ions and Fe2O3 prefer to form its former matrix, which confirm the dual role of Fe2O3 in the glass structure. The electric conduction process represents a feature of polaronic hopping conduction due to the presents of Fe2O3 as transition metal oxide.