الفهرس 
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Abstract
Two glass systems of binary CeO2 -B2O3 and ternary CeO2-PbO-B2O3 have been prepared and their structure has been characterized. Understanding and interpreting of data based on structural changes in the studied glasses upon addition of cerium oxide were of major interest. This may because of many commercial glasses containing some amount of such oxide (CeO2) are suitable in technological applications in various fields.The simultaneous introduction of CeO2 at expense of PbO within borate network brings even more complexity when defining the structure of such glasses. NMR magnetic resonance spectroscopy concerning 11B NMR has been carried out to offer specific information about the short-range ordered structure of glasses. NMR results gave detailed characterization on the structural role of cerium oxide for the first time. The structural features of borate glasses with addition of CeO2 have been shown to be dependent on the whole glass compositions. It was evidenced that increasing of cerium oxide content in glasses encourages the formation of more tetrahedral boron and cerium groups. The later units have a priority to bond with BO3 groups rather than to BO4 ones. Linking of CeO4 with BO3 units delays the conversion process from BO3 to BO4 units. Therefore, the B4 fraction of cerium borate glasses was lower than that of alkali borate glasses. CeO2 in such case is determined as an intermediate oxide. The structure of the studied cerium lead borate glasses was found to depend on structural factor CeO2/PbO. The related low changes in the region ≤ 10 mol% were referred to condition which forces both CeO2 and PbO to be participated in the borate network as glass modifiers. Consequently, replacing of PbO by CeO2 was found to have no effect on the well-formed BO4 fraction. In this situation, cerium oxide modifies B2O3 with the same manner of PbO. At higher cerium oxide concentration, CeO4 fraction was induced with increase in CeO2/PbO ratio. These features were correlated to the higher field strength of Ce as compared to Pb cations. Hence, some of modifying cations were preferentially associated with the higher field strength of Ce cations. As a result, CeO4 as a glass former units were the product which in turn linked with BO3 units causing frequent decrease in BO4 groups. The formation of CeO4 appeared to be favored in comparison to the formation of four-fold coordinated boron units. In such a case, continuous formation of CeO4 affected the concentration of four-fold coordinated boron in the glass. This effect is appeared in decreasing B4 fraction, since Ce–O–B3 bonds were created and highly affected the boron transformation. This variation was interpreted on base of structural role mainly played by CeO2 which acted as a network former in the investigated glasses. The well formed CeO4 was compensated by Pb2+ cations which were also consumed to compensate BO4 in the main glass matrix. FTIR spectroscopy was applied to determine the different functional groups constituting the matrix of the glass network. The determination of these groups was based on a quantitative measure of the fraction of four different tetrahedral units B4. Data obtained from FTIR technique is a complementary to those obtained from NMR spectroscopy. The higher concentrations from CeO2 significantly affected the obtained spectra. This effect resulted in wide overlapping and broadening in the absorption bands. To get quantitative results from FTIR spectra, a deconvolution of the strongest infrared envelopes into Gaussian components at different wavenumbers was performed. It is hardly to extract a specific information referred to each element shared in performing the spectra. This is because of great overlapping between mixed vibration modes of B-O and Ce-O in the spectral region ranged between 800- 1300 cm-1 which may be hardly to be separated. Therefore, we take the advantage of 11B NMR spectroscopy in correlation to FTIR to get a complete identification about structural role of Ce nuclei, which cannot be only measured by FTIR. In this respect, we analyzed FTIR spectra and determined the fraction of all four coordinated species, which is termed as B4. As well the fraction of boron in tetrahedral coordination N4 can be simply determined using the advantage of 11B NMR spectroscopy. Very obviously, the difference between B4 and N4 gives the fraction of Ce4. This approach is recommended to be applied to determine the fraction of elements which can’t be calculated from separated NMR and FTIR techniques. Using the advantage of both, the fraction of the concerning elements can be determined. The properties of glasses usually exhibit a considerable variation under the exposure to gamma rays. In general, the influence of irradiation occurred due to the rearrangement of chemical bonds and/or releasing electrons and holes inducing number of defects in the glass network. In this regard, FTIR was utilized to detect the radiation-induced changes in the structural properties of the studied system. At low CeO2 content, gamma radiation induced no obvious effectiveness in FTIR spectra due to the presence of high content of PbO. On other hand, pronounced variation in intensities of main structural groups increased with further increment of CeO2 at the expense of PbO. Irradiation effected on the characteristic of the bonding configuration into the local borate environment hence allowing more conversion from BO3 to BO4 to be encouraged and vice versa. Our additional objective in this study was to check up the validity of cerium oxide to transform the glass from commercial one to magnetic glass type for technical and scientific applications. The magnetization was found to be based on the CeO2 concentration, whether added as a dopant or additive. Thus, this work concentrated on the investigation of the magnetic properties of the studied glasses. The observation of hysteresis loop curve confirmed the room temperature ferromagnetic (RTferri-M) behavior for the studied system. The obtained results demonstrated the improvement in magnetization with CeO2 addition. The saturated magnetization and the total area of the hysteresis loop were found to have the same behavior. The relationship between the precipitates phases and magnetic clusters which determine the magnetic parameters has been clarified. Presence of some of crystalline phases were evidenced and confirmed by means of XRD, TEM and EDP measurements. Increasing in magnetic behavior of the studied glasses has been observed with addition of CeO2 content up to 20%. It was shown that this enhancement is strongly correlated with formation of crystalline phases enriched with cerium ions. Further increment in CeO2 (up to 30 mol% CeO2) caused an obvious reduction in saturation magnetization as well total area. This can be correlated with the nature of glass samples which characterized as amorphous materials. On other hand, samples with higher (x> 30 mol% CeO2) content showed a strong enhancement in the magnetization attributed to the high concentration of cerium ions. Both irradiation and heat treatment had considerable effect on the magnetic properties of the studied glasses but with different rate and roles. Heat treatment could enhance or decrease the magnetization depending mainly on cerium oxide content as well heating temperature and time. Meanwhile, irradiation induces a clear reduction in magnetization due to the formation of several types of defects. In particular, formation of color centers was found to be mainly responsible for inducing the irradiation damaging in the glass matrix. Moreover, cerium ions are expected to interrupt the formation of color center due to their capture abilities for trapping both electron (EC) and hole (HC) centers. This phenomenon was expected for increasing the irradiation damaging resistance in the irradiated glasses. As consequence, less reduction in magnetization of irradiated samples was detected with increasing cerium ions concentrations. Unexpected trend has been observed with the sample of highest CeO2 content (x=50 mol%) in contrast with the other glass samples. In such situation, CeO2 seemed to behave with different priority and this clearly appeared in FTIR, NMR and XRD spectra. This was mainly attributed to forming of CeO4 groups with a rate higher than that of BO4 units.