Date of Award
5-2024
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Materials Science and Engineering
Committee Chair/Advisor
Dr. Kyle Brinkman
Committee Member
Dr. Jianhua Tong
Committee Member
Dr. Mark Johnson
Committee Member
Dr. Pedro Groszewicz
Abstract
In this work, the hexagonal perovskite of targeted composition Ba5In2+xAl2Zr1-xO13 (x=0, 0.1, 0.2) was synthesized via a solid-state synthesis route to study the impact of oxygen vacancy concentration in layered hexagonal perovskites. Precursor oxides were mixed in stoichiometric proportions, calcined between 800-1200℃ and sintered at 1475℃. The sintered pellets were crushed into fine powders to investigate the chemistry and structure through X-ray diffraction, neutron diffraction, inductively coupled plasma mass spectrometry, and nuclear magnetic resonance. Dense pellets were used to study conductivity properties using electrochemical impedance spectroscopy.
The synthesis approach produced 100% phase pure material across a range of increasing indium content from 2.0 to 2.8, although not of the projected stoichiometries. Neutron diffraction and x-ray diffraction indicated fractional occupancy and site swapping of the indium and aluminum positions, which was not dependent on indium content and resulted in the newly detected O5 position.
From nuclear magnetic resonance, aluminum was proven to retain a strictly tetrahedral coordination. Additionally, the existence of four bulk protons was observed. Eight distinct oxygen signals were detected, likely the result of protonated and unprotonated forms of the various oxygen sites.
Impedance spectroscopy indicated a reduction of total conductivity at 600℃ from 10-4 to 10-5 S cm-1 from wet to dry air, with proton conduction consistent across the temperature range.
Recommended Citation
Cretegny, Nathan, "Layered Structure Protonic Ceramic Conductors of the Form Ba5In2+xAl2Zr1-xO13-δ" (2024). All Theses. 4273.
https://tigerprints.clemson.edu/all_theses/4273