Date of Award

12-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Committee Chair/Advisor

Joseph W. Kolis

Committee Member

William T. Penington

Committee Member

Juia Brumaghim

Committee Member

Rhett Smith

Abstract

Growing high-quality single crystals of transitional metal oxides have been of interest over the last two centuries because of the many applications of these transparent materials in various industries, such as optics, magnetism, semiconductors, and batteries. During this period, a variety of crystal growth techniques have been utilized, each offering unique advantages and disadvantages to the solid-state community.

Traditionally, metal oxides such as molybdates and vanadates are produced using high-temperature techniques (700 to 1200 °C). These methods can cause oxygen to be expelled, resulting in the creation of lattice defects and lower-valence metal ions and complicate precise measurements of physical properties. In contrast, hydrothermal crystal growth techniques are known as one of the most productive crystal growth techniques, especially for exploring novel crystalline complex metal oxides, since relatively lower temperature method (< 800 °C) minimizes the risk of metal oxyanion decomposition.

Herein, in this dissertation, novel first-row transition metal molybdates and vanadates are synthesized under low-temperature (200-220 °C) hydrothermal conditions to explore and identify new compounds and ultimately determine the thermal stability zone of the transition metal states. These reactions are conducted in aqueous solutions with different alkali and alkaline earth metal chlorides and carbonates serving as mineralizers in the Teflon acid digestion vessel, facilitating the synthesis of new low-temperature products.

First-row transition metals (TM), particularly those with unpaired electrons, have the capability to exhibit a range of intriguing magnetic properties, especially when constrained into triangular configurations, resulting in spin frustration.

Also, both Mo(VI) and V(V) are considered excellent building blocks for creating notable magnetic structures due to their stability and versatility Also, they are d0 and magnetically silent. So, the magnetic measurements in TM molybdates or TM vanadates are only reflected by TM cations in the structures. In addition, they can form tetragonal units that may cause geometric frustration due to their three-fold symmetry, which is useful for creating triangular symmetry in synthetic crystals.

Another aspect of this research is to study the role of mineralizers such as alkali chlorides and carbonates in forming novel transition metal molybdates and vanadates and their crystal growth. The role of carbonate, pH, and hydroxylated species is discussed.

This investigation resulted in a couple of alkali copper molybdates with full delta chains and Kagome lattice, and a series of novel alkali iron molybdates. In addition, several novel first-row transitional metal vanadates, including synthetic ronneburgite and its cobalt isostructural (K2M(VO3)4 (M = Mn, Co)), and family of CsM(VO3)2Cl (M = Mn, Co, Fe, Ni, Cu) are presented. This dissertation will explore the detailed structural characteristics and initial magnetic properties of these new obtained materials.

Author ORCID Identifier

https://orcid.org/0000-0003-3209-3283

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