Synthesis and Applications of Lanthanide Sulfides and Oxides

This dissertation focuses on two of the key fields where lanthanides find ready application: as optically active materials with a focus on the lanthanide sulfides, and as catalytic materials with a focus on cerium oxide. The lanthanide sulfides have attracted considerable interest for their potential as solar energy conversion materials, pigments, infrared window materials, and phosphor host media. However, applications of these materials remain limited due to their synthetic difficulty along with their not well understood properties compounded by both their difficulty in manufacturing as well as in simulating largely due to the need to take into account f-shell electrons. This dissertation presents the fundamental band properties of lanthanum, gadolinium, and samarium sulfides as well as a rapid chemical vapor deposition method for the synthesis of highly textured samarium sulfide thin films. Even more than the sulfides, the lanthanide oxides have attracted tremendous interest from industry and academia for their use as phosphors and catalytic applications, most notably cerium oxide in automotive three-way catalysts and in the petroleum industry as a cracking catalyst. In contrast to the lanthanide sulfides, the syntheses of the oxides are rapid and inexpensive causing many of the oxides to find ready applications even though the complexities of their chemistries are not yet well understood. This dissertation presents the fundamental kinetics and mechanism investigations for cerium oxide (ceria) as it is used for catalyzing the direct synthesis of organic carbonates from CO2 and methanol. Advisor: Chin Li “Barry” Cheun