الفهرس 
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Abstract
In the present work a nominal glass compositions [x mol% (TM) (60-x) mol% (P2O5) 40 mol% (SrO)] where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4 and 0.6 mol% (TM = CoO & C2O3) was successfully synthesized by using conventional melt annealing technique. Structural, optical, and electrical properties of the prepared strontium phosphate glass compositions doped with x mol% of transition metal oxide (CoO & Cr2O3) were studied. The structural properties are characterized by various techniques such as X-Ray diffraction (XRD), Fourier-Transform-Infra-Red (FTIR) and NMR spectroscopy. The powder X-Ray diffraction analysis of the prepared glass compositions confirms the amorphous nature of the prepared samples. The study of both NMR and FTIR spectra of Cr2O3 and CoO doped SrO-P2O5 glasses can be used for revealing the different atomic arrangements in the investigated glasses. These tools are very sensitive to the local symmetry, the character of the chemical bond and other additional structural properties. In undoped SrO-P2O5 and Cr2O3 doped SrO-P2O5 glasses, the FTIR and NMR of 31P spectra showed some differences, while there are no any observed differences between CoO free SrO-P2O5 glass and of glass containing CoO. These results indicate that there is no any tendency for CoO to form glass via Co-O-P constituent and the limited concentration from CoO is not accessible to induce any related change in the glass structure. The situation is totally differed in the case of doping by Cr2O3 since there are some differences between the structure of glass free from Cr2O3 and glasses containing Cr2O3. Presence of Cr2O3 has an effective influence on the chemical shifts (ᵹ) of P nuclei since the value of ᵹ is decreased upon incorporation of Cr2O3. The value of ᵹ for base glass is -21 ppm, while ᵹ of glass containing traces from Cr2O3 is appeared at -24 ppm. In addition, a new resolved resonance band centered at -34 ppm appears only in the glass containing Cr2O3. Changes of ᵹ to more negative values may lead to a reduction in the concentration of non-bridging bonds and formation of new phosphate species with more bridging oxygen atoms (Q3). from the FTIR spectra upon increasing Cr2O3 content, the wide hump lies in the region between 800-1200 cm-1 becomes narrower and contains sharper envelops for all doped glasses which may indicate the formation of mixed P-O-Cr bonds indicates increasing number of Q2 to reach Q3 units. from the analysis of the absorption spectra of CoO free SrO-P2O5 glass and of glass containing CoO, it is clear that there is a strong band at 220 nm attributed to the trace iron impurities of raw material. When the addition of CoO, a broad strong visible band revealing three peaks at 532, 583 and 621 nm and finally succeeded with three separate small bands at about 1370, 1528 and 1720 nm. It is accepted that the divalent cobalt ions exist in two coordination forms, namely octahedral and tetrahedral states. Glasses containing CoO show a distinctive and interesting bluish color. While for the prepared strontium phosphate free from Cr2O3 and containing Cr2O3 glass, there is a strong band at 220 nm attributed to the trace iron impurities of raw material which is used to prepare samples. But another six absorption peaks appeared in Cr2O3-SrO-P2O5 glasses. Indicating that Cr2O3 exists in more than coordination states (Cr6+ & Cr3+). The base SrO-P2O5 glass is colorless and transparent, on the other hand, green appearance is visible for glasses containing Cr2O3, and dark green is appeared with increasing Cr2O3 content. Refractive index (n), extinction coefficient (k), real (ε1) and imaginary (ε2) parts of complex dielectric constants are calculated optically and found that the values of them increase when increasing their concentration. It was found that the value of band gap depends on CoO & Cr2O3, and the energy gap values decrease with increasing CoO & Cr2O3 content. The electrical conductivity, dielectric constant, dielectric loss and electrical modulus of undoped and doped prepared samples were investigated. The ac electrical conductivity follows a power law of the frequency σac = Aωs. At high frequency, where s is dependent on temperature, the conduction mechanism is reasonably well interpreted in terms of the correlated barrier hopping model. The electrical conductivity showed an increasing behavior with increasing both frequency and temperature at fixed glass. On the other hand, the real and imaginary parts of dielectric constant and dielectric loss showed a decreasing trend with increasing frequency for all prepared samples. In addition, the frequency exponent (s) is observed to decrease with increasing temperature, where 0.5 ≤ s ≤ 1. Based on the obtained data, it is suggested that the correlated barrier hopping (C.B.H.) is the suitable conduction mechanism in the investigated glasses. Electrical conductivity was identified to decrease with increasing doping (CoO & Cr2O3) concentration.