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Title: Radiation damage and helium bubble formation in Ca(1-x)La(2x/3)TiO3 perovskite ceramics
Author: Lawson, S. M.
ISNI:       0000 0004 7655 3613
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Phase transitions within the Ca1-xLa2x/3TiO3 A-site deficient perovskite system using XRD and electron diffraction have been identified as Pbnm for 0 ≤ x ≤ 0.5, Ibmm for x = 0.6, I4/mcm for x = 0.7, Cmmm for x = 0.9, while a single-phase product for the x = 0.8 sample could not be confirmed. A-site cation/vacancy ordering was observed in the x = 0.7 and 0.9 samples through electron diffraction. Nanocrystallite formation within A-site deficient samples was observed due to low energy Ar+ ion milling. Bulk 1 MeV Kr+ and 5 MeV Au+ ion implantation of the A-site deficient perovskite system Ca1-xLa2x/3TiO3 was undertaken to fluences of 1 x 1015 ions cm-2 and 5 x 1014 ions cm-2 , respectively. A-site deficiency enhanced resistance to amorphisation has been observed for the 0.2 ≤ x ≤ 0.4 region, followed by a reduced resistance to amorphisation region for x ≥ 0.5. A saturation of radiation damage induced volume swelling was observed for the x = 0 and 0.5 samples, while volume swelling was not observed for x ≥ 0.6 samples. The enhanced resistance to amorphisation observed was not related to structure and is likely directly related to the induction of A-site vacancies. Helium bubble formation was investigated within the Ca1-xLa2x/3TiO3 system, investigated using 6 keV He+ ion implantation in-situ in a TEM. The fluence for observable bubble formation remained within error for the x = 0, 0.2 and 0.4 samples, suggesting enhanced resistance to amorphisation supresses helium bubble formation in the x = 0.2 and 0.4 samples. Preferential bubble formation was observed within grain boundaries, increasing the required fluence for helium bubble formation in the bulk. The fluence required for helium bubble formation was reduced in the x = 0.2 sample when ion implanted at 823 K.
Supervisor: Hyatt, Neil ; Gandy, Amy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available