“Determination of structure and microstructure of materials of technological interest (nanocrystalline TiO2, High Temperature Superconductor) using XRPD”

Postgraduate Thesis uoadl:1321499 600 Read counter

Unit:
Κατεύθυνση Φυσική των Υλικών (ΒΑΣΙΚΗ ΦΥΣΙΚΗ)
Library of the School of Science
Deposit date:
2015-06-08
Year:
2015
Author:
Χρύση Αντιγόνη
Supervisors info:
Μαρία Καλαμιώτου Aναπληρώτρια Καθηγήτρια
Original Title:
«Προσδιορισμός δομής και μικροδομής υλικών τεχνολογικού ενδιαφέροντος (νανοκρυσταλλικό TiO2, υπεραγωγός υψηλών θερμοκρασιών) με XRPD»
Languages:
Greek
Translated title:
“Determination of structure and microstructure of materials of technological interest (nanocrystalline TiO2, High Temperature Superconductor) using XRPD”
Summary:
The determination of the structure of different materials is essential for the
understanding of their physical properties. Furthermore, for materials of
technological interest, it is particularly important to understand the
characteristics of their microstructure, i.e., the average crystallite size /
coherently diffracting domains and crystallite microstrains. The X-ray powder
diffraction (XRPD) is one of the principal methods for determining the
structure and microstructure parameters of polycrystalline materials. In this
work two different materials of technological interest, nanocrystalline TiO2
and the high temperature superconductor (Y-Pr) 123, are studied by XRPD, using
Rietveld analysis which incorporates the microstructural parameters.
Titanium dioxide (TiO2) has been the most widely used photocatalyst in the
degradation of liquid and air pollutants. The photocatalytic efficiency of TiO2
greatly depends on the optimal combination of structural-microstructural
characteristics such as the crystalline phase and the small nanocrystallite
size (high surface area) and the low density of crystal defects. To this aim,
we have studied the effect of calcination temperature on the structure and
microstructure of nanocrystalline TiO2 and the relationship between
microstrains / crystalline quality and structural characteristics / size of
crystallites.
The compound Y1-xPrxBa2Cu3Oy ((Y-Pr) 123) is a high temperature superconductor.
In the (Y-Pr) 123 compounds the superconducting critical temperature (Tc)
decreases monotonically with increasing amount of Pr. We have studied the
effect of substitution of Y for Pr in the structure and microstructure of the
Y1-xPrxBa2Cu3Oy (x = 0.0-0.5) samples, which have been synthesized by the
solid-state reaction method. Increasing Pr content leads to changes in the
structural characteristics (lattice parameters, bond length) as well as
increased microstrains, i.e. a distribution of lattice parameters, which
indicates the increase of crystalline defects and / or inhomogeneities of
chemical composition in crystallites.
Keywords:
XRPD, Structure, Microstructure
Index:
Yes
Number of index pages:
2
Contains images:
Yes
Number of references:
19
Number of pages:
71
File:
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