الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Amorphous solids, because of their microscopic structure, occupy a unique position among the condensed state of matter.
In an overall look, glass was recognized by early civilizations such as discovered in Egypt dated back to the year 7000 B.C. Glasses are super cooled liquids characterized by the lack of longrange order. Lithium diborate (Li2B4O7) based glasses constitute a relatively new class of vitreous materials. This class is of scientific and technical interest as a result of their low melting point, high refractive indices, high dielectric constant and good IR transmission. Their chemical durability is good. (Li2B4O7) in combination with some transition metal oxides such as MoO3 which form stable and high dielectric glasses. Furthermore, the structure of lithium borate – based glasses is of interest of its high rigidity.
Infrared spectroscopy is one of the most important analytical techniques due to its advantage of the ability of studying any sample in any state. FTIR spectroscopy is a technique based on the vibrations of the atoms of a molecule. An IR spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed, spectrum appears corresponds to the frequency of a vibration of a part of a sample molecule.
This work aims to characterize the lithium borate glasses by using IR analysis, and both the UV-VIS- NIR transmission and reflection measurements to study the structural variation in these glasses with different MoO3 contents . The structural variation will be studied in terms of the IR shift, the optical properties determined from an experimental technique (UV-VIS- NIR absorbance and reflection).
Hence, the preparation of MoO3–Al2O3–Li2O–B2O3 glasses were carried out by conventional melting and annealing technique. Al2O3was added to the suggested chemical compositions of these glasses in order to improve their chemical durability and stability. Dimensional adjustment and polishing of the glass samples were done in order to prepare them for each specific property measurement, have been followed.
Differential thermal analysis (DTA) was performed on finely powdered glass using a Shimadzu DTA-50 (Kyoto, Japan-1990) analyzer with heating rate of 10 ºC min−1 and with Al2O3 as the reference material. Crystallization temperatures were identified from the DTA traces and the glasses were subjected to heat treatment schedules corresponding to each crystallization temperature. The heating rates used were 10 ºC min−1.
X-ray diffraction analysis was used to confirm the amorphous nature of the as-quenched glasses and to investigate the phase composition of the produced glass ceramics using a Philips powder diffractometer with Ni-filtered Cu-Kα radiation (λ=1.54178 Å). The phases formed were identified by comparing the experimental diffraction patterns with the powder diffraction database.
A Jeol (JSM-T20, Tokyo, Japan) scanning electron microscope (SEM) was used to record backscattered electron images of the microstructure of the produced glass-ceramics.
The infrared absorption spectra of the glasses in the wave number range of 400 - 4000 cm-1 with a resolution of 4 cm-1 were measured at room temperature by an infrared spectrophotometer type JASCO, FT/IR – 430 (Japan), using the KBr pellet technique. The infrared spectra were corrected for the dark current noises, and normalized to eliminate the concentration effect of the powder sample in the KBr disc.