الفهرس 
Chapter 1 :Introduction and Letrature reviewOnly 14 pages are availabe for public view
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Abstract
New tellurite glasses within composition 75TeO2–5WO3–15Nb2O5–5MxOy in mol%, where MxOy = (Na2O, Ag2O, ZnO, MgO, CuO, NiO, TiO2 and MnO2), have been prepared using the conventional melt-quenching method. The optical properties of these glasses were estimated by measuring the ultraviolet–visible–near infrared (UV–vis–NIR) spectroscopy and linear refractive indices at different wavelengths. from the absorption edge studies, the values of the optical band gap (Eopt) and Urbach energy (ΔE) were evaluated. The density, molar volumes, molar refraction (Rm), molar polarizability (αm), metallization criterion (Mc), electronic polarizability of oxide ions ( ), and optical basicity (Λ) were estimated. Moreover, the nonlinear refractive index (n2), third-order nonlinear susceptibility (χ(3)), and nonlinear absorption coefficient (β) were observed. It was found that the linear and nonlinear refractive indexes increase with decreasing the optical energy gap. It was found that the glass with the composition 75Te2O-5WO3-15Nb2O5-5CuO had very high value of nonlinear absorption coefficient (β = 421.35 cm/GW ) , The largest value of the third-order nonlinear optical susceptibility (χ(3) = 6.7× 10-13 esu) (i.e 28 times of fused silica) and the largest value of the non-linear refractive index (n2 = 5.4×10-15 cm2/W) (i.e 18 times of fused silica).
Thermal characteristic of prepared glasses were investigated by using DTA techniques. It was found that the glass with the composition 75Te2O-5WO3-15Nb2O5-5TiO2 had high thermal stability (ΔT =122 Cᵒ at heating rate 15 K/min). Raman gain coefficients and bandwidths of prepared glasses for Raman gain media were evaluated. The glass with composition 75TeO2- 5WO3- 15Nb2O5- 5Na2O had the maximum value of Raman gain coefficient (g =4.43 ×10-12 m/W) and it was 24 times as large as silica glass. The highest value of full width half maximum (FWHM = 185 cm-1) was observed in glass system 75TeO2- 5WO3- 15Nb2O5- 5NiO. The structure of the glasses was investigated through deconvolution Raman and IR spectra.
The transmission curves of the glass systems 75TeO2- 5WO3- 15Nb2O5- 5NiO, 78TeO2- 5WO3- 15Nb2O5- 2NiO and 78TeO2- 5WO3- 15Nb2O5- 2NiCl introduce them as a band pass filters with two symmetrical bands , they also can be used as an optical limiters (i.e pass the intense laser beam with a lower intensity).
Both longitudinal (VL) and shear (VS) ultrasonic velocities of the prepared glass systems were measured by using the pulse-echo method at 5 MHz frequency and at room temperature. Ultrasonic velocity and density data have been used to calculate elastic moduli (longitudinal modulus (L), shear modulus (S), young’s modulus (E), Bulk modulus (K), Hardness (H), Poisson’s ratio (σ), and Debye temperature (θD). they showed similar behaviour to the ultrasonic velocities. Quantitative analysis of elastic moduli based on the number of bonds per unit volume (nb), average crosslinks (nc) , the ionicity of the modifier (I) and the ratio TeO3/TeO4 has been achieved.
The decrease in elastic moduli is suggested to be due to weakening of network rigidity of the glass system due to the increase of the ionicity of the modifier and in turn increase in formation of non-bridging oxygen, NBO as revealed by Raman spectroscopy. Additional analysis using Makishima and Mackenzie model ,The results show a good agreement between experimental and calculated values of the elastic moduli E, K, S and σ.