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Molecular Dynamics Modelling of Barium Silicate and Barium Fluorozirconate Glasses

Rai, Maha (2018) Molecular Dynamics Modelling of Barium Silicate and Barium Fluorozirconate Glasses. Doctor of Philosophy (PhD) thesis, University of Kent,. (Access to this publication is currently restricted. You may be able to access a copy if URLs are provided) (KAR id:66702)

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Language: English

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Abstract

Advancement in science and technology has profoundly depended on new types of glass innovation. The glasses that were studied in this project are binary barium silicate glasses, binary barium fluorozirconate glasses, ZBLAN glasses and ?Eu?^(3+) doped ZBLAN glass (the ZBLAN glasses are based on binary barium fluorozirconate glass). The high atomic number of barium in the barium silicate glasses provides high mass and high electron density providing its applications for heat and X-ray shielding. The phenomena such as phase separation in the barium silicate glass will affect its properties of durability and electrical conductivity. On the other hand, ZBLAN glasses have a broad infrared optical transmission window due to the weaker bonding/interaction of F^- ions. Due to the presence of lanthanum in the composition ZBLAN glass can be easily doped with rare-earth ions such as ?Eu?^(3+) giving it many optical applications such as optical amplifier and fibre lasers.

The structure analysis was performed at short-range order (e.g. coordination number, bond length and bond angle), medium-range order (e.g. network connectivity) and long- range order (e.g. phase separation). The related crystals were also simulated in similar conditions to the glasses to compare their atomic structure. Normally at short-range order glass

new methods such as rotational invariants and grid analysis were used to scrutinise structural units and phase separation respectively.

The structural units of fluorozirconate glasses were carefully studied as they do not follow the Zachriasen glass model. The coordination number for Zr was mixture of 7 and 8. The rotational invariant analysis shows that the structural units of ZrF_n polyhedra for coordination number 7 and 8 were similar to Augmented Triangular Prism and Biaugmented Triangular Prism respectively. However, rotational invariant values for BaF_n polyhedra tend more towards random.

The large complex model of ?Eu?^(3+) doped ZBLAN glass was made as it is studied for optical applications. The initial analysis was to observe whether Zr and Ba has similar structural roles as in binary fluorozirconate glass system which they do. Considering the extra elements in ZBLAN glass, Al behaves like a network former and has octahedra structural units whereas La and Na behave like modifiers. In the glass Eu was uniformly distributed with predominantly coordination number of 8 and does not have well defined structural units.

Item Type: Thesis (Doctor of Philosophy (PhD))
Thesis advisor: Mountjoy, Gavin
Uncontrolled keywords: Molecular Dynamics; Rotational Invariants; Grid Analysis; Glasses; Alkaline Silicate; Zirconium Fluoride; ZBLAN
Divisions: Faculties > Sciences > School of Physical Sciences
SWORD Depositor: System Moodle
Depositing User: System Moodle
Date Deposited: 12 Apr 2018 11:26 UTC
Last Modified: 27 Jan 2020 04:10 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/66702 (The current URI for this page, for reference purposes)
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