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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemistry

Year Degree Awarded

2017

Month Degree Awarded

February

First Advisor

Kevin R. Kittilstved

Subject Categories

Inorganic Chemistry | Materials Chemistry

Abstract

Strontium titanate is a wide gap oxide perovskite that has been studied for numerous applications. Its potential use as a photocatalyst is limited due to only being able to utilize UV light. The introduction of metal dopant ions has been shown to alter the band structure to allow visible light photocatalysis, as well as alter the materials properties for other applications. This work will look to better explain the process of transition metal dopant ion incorporation and how the dopant ion can affect the defect chemistry of the material.

The use of dopant specific spectroscopies, such as electron paramagnetic resonance (EPR) spectroscopy for paramagnetic dopant ions, is critical to fully understand the incorporation dopant ions into the lattice. Through the use of systematic studies and correlating dopant valence state to formation of the materials. This also allows for the determination of the dopant location, i.e. internal, surface, clustered, which can affect the properties further.

Through the use of an adapted NaBH4 reduction method, the valence state of the dopant ion is altered as shown using quantitative EPR spectroscopy and the corresponding changes in the absorption of these reduced materials is shown. The correlation to the dopant ion control and changes in the VO defects charge state to act as charge compensation was studied in order to better understand methodologies for additional control in the photocatalysts.

The incorporation of dopant ions into the Ruddlesden-Popper phase Sr2TiO4, a layered perovskite, is also described herein, including the determination of EPR parameters and dopant specific emission spectroscopy. The changes in these materials as it relates to controlling the valence state of dopant ions and altering the defect chemistry in the lattice are also studied using the NaBH4 reduction.

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