Date of Award

2018-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

Rosa Fitzgerald

Second Advisor

Cristian E. Botez

Abstract

Proton conductor solid acid electrolytes RbxCs1-xH2PO4 (0≤x≤1) have been investigated using second harmonic generation and powder x-ray diffraction. Second harmonic generation is an optical technique which can be used to study the structural properties of materials. Microscopes of this nature have the ability to image objects with a variable penetration depth in a non-destructive manner, allowing for great potential to be used for in situ observations of the electrolyte’s structure when in a fuel cell under operating conditions.

X-ray powder diffraction was carried out on the series of samples and found for values of 0≤x≤0.5 the structure of the material is monoclinic P21/m, for 0.6≤x≤0.8 the material exhibits peaks that follow the monoclinic structure, however are joined by new signatures which are found in the 0.9≤x≤1 samples which have a tetragonal I-42d structure. Unique structural changes are observed in the 0.6≤x≤0.7 samples which appear to be mixtures of the tetragonal and monoclinic phases of the material, as was supported by energy dispersive spectroscopy.

Second harmonic generation was carried out on the series of samples with only the 0.6≤x≤1 samples exhibiting a signal. The polarization dependence of the material yielded two distinct behaviors; dipolar behavior in the 0.6≤x≤1 (where x ≠ 0.8) samples, and quadrupolar behavior in the x = 0.8 sample. SEM/EDS were employed to investigate composition and morphology of the SHG exhibiting regions.

Language

en

Provenance

Received from ProQuest

File Size

75 pages

File Format

application/pdf

Rights Holder

Alex D. Price

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