Resume  

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          My master research entitled “Synthesis, spectroscopic and molecular dynamic simulations of Eu3+-doped alkali aluminosilicate glasses” presents the investigation of fluorescence spectroscopy and structural analysis using molecular dynamic simulations (MD) of alkali aluminosilicate (AS) glasses doped with 1 mol% of Eu2O3.

 

          In the first part, synthesis of Eu3+-doped alkali aluminosilicate glasses of the molar composition 20 M2O·20 Al2O3·60 SiO2 (M=K, Li and Na) were prepared by using the melt quenching technique.

The investigation of the luminescent properties were studied by recording the excitation/emission spectra in the visible range. The asymmetry ration was also calculated. It gives an idea about the degree of distortion of the environment. The highest ratio was found for glasses with heavy network modifying such as KAS2020.

The CIE 1931 chromaticity diagram has characterized the attributed luminescence color of the studied samples under an excitation wavelength at 465 nm, the color coordinates x and y for LiAS2020, KAS2020 and NaAS2020 are found to be 0.64 and 0.35. They are very close to the reddish orange region.

In addition, lifetime measurements were calculated. LiAS2020 was found to have the higher lifetime value.

 

           In the second part, structural analysis were carried out by means of MD simulations using a potential developed by Pedone et al. Two glass samples were studied: LiAS2020 and KAS2020 doped with Gadolinium oxide in function of the system size. The results of these MD simulations have shown that there is no system size effect in the coordination number (CN) and in the radial distribution function (RDF) for the studied pairs. A slight system size impact was observed in the relative number of bonding oxygen (BO), non-bonding oxygen (NBO) and triclusters. The found results showed that Si and Al have a coordination number of four, independently of the glass composition and the system size.

However, the incorporation of alkali cations lowers the liquidus and changes the structure. It engenders the formation of NBO and triclusters in the network. The results obtained clearly demonstrate the possibility of forming NBO atoms in AS glasses with the molar fraction ratio Al2O3/M2O=1.  The fraction percentage of Oxygen entities have shown that BO are the most present species in the structure followed by NBO and triclusters. The structures involve also the formation of Al-O-Al bonds, which are reflecting a deviation from the Lowenstein rule.

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 Publications  

 

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