الفهرس 
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Abstract
To investigate the structure of these glasses, quantitative FTIR analysis was used and the correlation between the physical properties and the glass structure has been investigated. Glasses of the formula xCdF2(100 – x)B2O3 (40 ≤ x ≤ 80 mol%) have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XRD patterns reveal the amorphous nature of investigated glasses for CdF2 up to 75mol%. The pattern of the sample containing 80 mol% CdF2 shows different sharp peaks revealing presence of crystalline species. The SEM shows amorphous agglomerates having laminar nature dispersed in the glass matrix are amorphous, up to 75 mol% CdF2. N4, values predicted from IR spectra of CdF2-B2O3 glasses show a linear increase of about 0.06 between 40 and 75 mol% CdF2. Infrared results revealed partial modification of the borate network, where BO3 units are converted to tetrahedral units B4 units with B-F linkage. The residual part of CdF2 forms its own matrix in the form of amorphous and crystalline phases, built of CdF4 tetrahedral. Calculated values D and Vm based on the concentration of structural units agree well with the experimental data. There is a steady increase in density with increasing CdF2 content. Cd2+ ions in tetrahedral units are considered as the dominant charge carriers up to ~60 mol% CdF2 and F– ions are the main type at higher CdF2 contents XRD patterns of xPbF2∙(45 – x)CdF2∙55B2O3 (0 ≤ x ≤ 45 mol%) glasses indicated that there are no crystalline phases in these glasses. On contrary, SEM of 25PbF2∙20CdF2∙55B2O3 glass revealed separation of PbF2-rich phase and limited concentration of CdF2 crystallites. It is assumed that Pb2+ and Cd2+ ions have mutual ability to activate phase separation of phases related to each other. IR spectra have been analyzed to follow the change in concentration of structural species. It is assumed that both CdF2 and PbF2 partially modify the borate network, forming tetrahedral borate units and the rest forms CdF2 and PbF2 amorphous matrices. The concentration of structural units has been employed to calculate the density and molar volume. It has been found that the volumes of structural units in the studied glasses are the same in CdF2–B2O3 and PbF2–B2O3 glasses. An increase in the activation energy for conduction up to 15 mol% PbF2, accompanied by a small increase in the conductivity suggest that Cd2+ ions are the dominant mobile species in that region. F– ions in PbF2-rich phase are assumed being the main charge carriers for PbF2 > 15 mol%, where a fast decrease in the activation energy and an increase of more than four orders of magnitude in conductivity are observed. XRD patterns of selected samples of the series xBaF2•(45 – x)CdF2•55B2O3 show broad humps, which reflect amorphous structure. Nevertheless, there are features of some crystallinity in the pattern of 45BaF2•55B2O3 glass. SEM micrographs of 25BaF2•20CdF2•55B2O3 show less grain number than the glass 45CdF2•55B2O3. Micrographs of the glass 45BaF2•55B2O3 show formation of laminar condensed agglomerates of much greater size FTIR spectra of xBaF2•(45 – x)CdF2•55B2O3 glasses can be deconvoluted to get the fraction N4 of B4 units. There is a linear change in both D and Vm as a function of BaF2 content. It interesting to note that D decreases upon replacing CdF2 by BaF2. An opposite change was to be expected, since the relative molecular mass of BaF2 is greater than that of CdF2. D must be correlated with the type and distribution of structural units. Calculated D and Vm values agree very well with the experimental data. The difference in the rates of change in (fVuDu)Cd+B and (fVuDu)Ba is the reason of decrease in density of xBaF2•(45 – x)CdF2•55B2O3 glasses upon increasing BaF2. The amorphous of the prepared glass sample of composition xPbF2∙(45 – x)CdF2∙55B2O3 was confirmed by XRD and SEM. The variation in density or molar volume with composition is correlated with the type and concentration of structural species, rather than the molar mass. N4 data of glasses from CdF2-B2O3 have been used to determine the concentration of structural units. The increase in E and the limited change in conductivity suggest that Cd2+ ions are the main charge carriers up to 15 mol% BaF2 The decrease in E and increase in logσ673 for BaF2 > 15 mol% reveal that BaF2 starts to be the dominant conducting matrix. So, it is assumed that in the region 15 ≤ BaF2 ≤ 35 mol% the modifier Ba2+ ions in tetrahedra might be the most effective transport species. Afterwards, diffusion of F− free vacancies in BaF2 matrix may dominate the conduction process for BaF2 > 35 mol%. This implies interconnection of BaF2 agglomerates in the region of BaF2 > 35 mol%.