الفهرس 
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Abstract
In the present work a nominal glass compositions [x mol% (Li2O) (30-x) mol% (Na2O) 65 mol% (B2O3):5 mol% RE] where x=0, 10, 20 and 30 mol% (RE= Sm2O3, Nd2O3) was successfully synthesized by using conventional melt annealing technique.
Structural, optical, electrical and mechanical properties of the prepared lithium sodium borate glass compositions doped with 5mol% (sm2O3, Nd2O3) before and after irradiated with 80KGy gamma dose were studied as a functional of lithium oxide content.
The structural properties are characterized by various techniques such as x-ray diffraction (XRD) and Fourier-Transform-Infra-Red (FTIR) spectroscopy. The powder x-ray diffraction analysis of the prepared glass compositions confirms the amorphous nature of the prepared samples. Fourier transform infrared analysis of the prepared samples revealed the formation of BO3 and BO4 group upon addition of lithium oxide content and network structure of the prepared samples is mainly based on the BO3 and BO4 units.
The density of the prepared lithium sodium borate glass compositions doped with 5mol% Sm2O3 is found to be increased from (2.876-4.315) gm/cm3 with increasing Li2O content from (0-20) mol% then decreased to 3.45 gm/cm3 at 30 mol% while molar volume is found to decreased from (28.262-17.349) cm3/mol with increasing Li2O content from (0-20) mol% then increased at 30mol% to 20.756 cm3/mol. While for prepared lithium sodium borate glass compositions doped with 5mol% Nd2O3, density decreased from (2.475-2.434) gm/cm3 with increasing Li2O from (0-20) mol% then increased to 2.461 gm/cm3 at 30 mol%, and molar volume decreased from (32.593-28.860) cm3/mol. with increasing Li2O content from (0-30) mol% respectively.
from the analysis of the absorption spectra of the prepared lithium sodium borate glass composition doped with 5mol% (Sm2O3) before gamma irradiation, it is clear that, there are existing a strong visible peaks at 402 nm for 0 of Li2O, at 424 nm for 10 mol% for Li2O and at 402 nm, 478 nm for 20 mol% and 30 mol% of Li2O. In addition there exist seven absorption peaks for all lithium oxide content lying in the wavelength range between (900-1600) nm which corresponding to transitions of Sm+3 ions from ground state (6H5/2) to the various excited states. While for the prepared lithium sodium borate glass compositions doped with 5mol% Nd2O3 before gamma irradiation, there are ten absorption peaks for various lithium oxide content lying in the wavelength range between (185-900) nm, which corresponding to transitions of Nd+3 ions from ground state (4I9/2)to various excited states. The effect of gamma irradiation indicated that, the spectrum has the same behavior that of the un-irradiated glasses composition with no distinct variations in the NIR absorption region, no change of shift in the peak position but the change is observed in their intensities.
The analysis of the absorption coefficient data for the prepared lithium sodium borate glass compositions doped with 5 mol% (Sm2O3 and Nd2O3) for all lithium oxide content before and after irradiated with 80 KGy gamma dose revealed the existence of allowed indirect transition. The optical constants (α,n,k) optical energy gap, Urbach energy tail, linear optical susceptibility χ(1), third order of non-linear optical susceptibility χ(3), non linear refractive index n2 have been calculated. It was observed that the value of optical energy gap depends on lithium oxide content and γ-irradiation. Optical energy gap of prepared lithium- sodium borate glasses doped with 5mol% Sm2O3 increases from (3.15-3.3) eV and from (2.93-3.09) eV with increasing Li2O content from (0-20) mol%, then decreases to 3.24 eV and 2.85 eV at 30 mol% before and after irradiated with 80 KGy gamma dose, respectively. While Urbach energy tail decreases from (0.119-0.095) eV and from (0-20) mol% then increased to 0.114 eV and to 0.512 eV at 30mol% before and after irradiated with 80 KGy gamma dose respectively. On the other hand, for prepared lithium sodium borate glasses doped with 5mol% Nd2O3, optical energy gap decreases from (3.325-3.0) eV and from (3.2-2.915) eV with increasing Li2O content from (0-20) mol%, then increases to 3.115 eV and 3.04 eV at 30 mol% before and after irradiated with 80 KGy gamma dose, respectively. Urbach energy tail increases from (0.4001-0.486) eV and from (0.845-0.953) eV with increasing Li2O content from (0-20) mol%, then decreases to o.436 eV and to 0.646 eV at 30mol% before and after irradiated with 80 KGy gamma dose, respectively. The linear optical parameters n0, χ(1) and non-optical parameters χ(3),n2 of the lithium sodium borate glasses doped with 5mol% Sm2O3 have been estimated from the obtained values of refractive index (n) and optical energy gap (Eg). It was found that values of n0, χ(1), χ(3) and n2 before gamma irradiation dose vary from (2.358-2.335), (0.363-0.354) esu, (1.733-1.1.577)x10-12esu and (27.71-25.467)x10-12 esu with increasing Li2O from (0-30) mol% respectively. After irradiated with 80 KGy gamma dose, their values were found to vary from (2.416-2.635), (0.385-0.473)esu, (2.2-5.0)x10-12esu and (34.277-71.626) x10-12esu with increasing Li2O content from (0-30) mol% respectively. On the other hand, with respect to lithium sodium borate glass doped with 5mol% Nd2O3, the values of n0,χ(1), χ(3) and n2 before gamma irradiation were found to vary from (2.315-2.314), (0.347-0.346)esu, (1.45-1.44)x10-12esu and (23.6-23.5)x10-12esu with increasing Li2O content from (0-30)mol% respectively. After irradiated with 80 KGy gamma dose, their values were found to vary from (2.41-2.387), (0.383-0.374)esu, (2.151-1.961)x10-12 and (33.636-30.949)x10-12esu respectively.
The ac electrical conductivity, dc electrical conductivity and the dielectric constants of lithium sodium borate glasses doped with Sm2O3 and Nd2O3 were investigated. from the experiment of dc electrical conductivity σdc at various temperatures, it was found that, the dc electrical conductivity increases with increasing absolute temperature and Li2O content. It was also found that thermal activation energy decreases from (1.263-0.832) eV and increases from (0.831-0.988) eV with increasing Li2O content, in case of doping with Sm2O3 and Nd2O3 respectively.
The ac electrical conductivity follows a power law of the frequency σ(ω) α ωs. 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 dielectric constant and dielectric loss of lithium sodium borate glasses doped with Sm2O3 and Nd2O3 decrease with increasing frequency and increase with increasing temperature. Thus, the Ac electrical conductivity, the dielectric constant and the dielectric loss of studied compositions seem likely to be both frequency and temperature dependent.
The mechanical properties represented by hardness for lithium sodium borate glass compositions doped with 5mol% of Sm2O3 for various lithium oxide contents before and after irradiated with 80KGy gamma dose have been characterized.
Micro indentation technique was employed to evaluate the hardness. This investigation reveals a variation of hardness with Li2O content. It was found that Vickers hardness number Hv increases from (4.93-5.26)GPa and from (5.08-5.34)GPa with increasing Li2O content from (0-30)mol% for lithium sodium borate glass compositions doped with 5mol% Sm2O3 before and after irradiated with 80KGy gamma dose respectively.
Key Words: gamma irradiation, rare earth, borate glass, nonlinear optics, Ac conductivity, FTIR spectroscopy, absorbance, hardness.