| In contrast to their extreme rarity, the transition metals technetium and rhenium have an extensive and rich chemistry. Technetium (Z = 43) was the first artificial element to be discovered, and rhenium ( Z = 75) the last naturally occurring element to be found. Easily the most important application of Tc is the use of its metastable isotope 99mTc in nuclear medicine diagnostics. Consequently, the coordination chemistry of Tc has been studied extensively while its solid state and occasionally fundamental chemistry have lagged behind considerably. This gap in knowledge has left the subject of solid state studies of Tc a green field in which to make new discoveries and find new materials. The work presented includes such investigations on the solid-state chemistry of Tc and Re containing oxides. In this dissertation the general methodology employed to study these materials includes preparation, structural characterization with X-ray and neutron diffraction, first-principles calculations to simulate their electronic structures, and finally magnetometry measurements to understand their magnetic behavior.;The investigations undertaken in this dissertation have been organized into three major areas: (i) The study of the structure, properties, and metal-metal interaction in the binary oxide TcO2, (ii) investigations of new and known ternary oxides containing Tc, and (iii) the study of the negative thermal expansion properties of the metallic oxide ReO3. The bulk of this work concentrates on new ternary oxide phases with Tc in various oxidation states including Bi2Tc2O7, Bi 3TcO8, Bi3Tc3O11, Cd 2Tc2O7, and CdTcO3. Related but previously known ternary oxides also presented in these studies include Pb2Tc 2O6 and SrTcO3. The structure types of all the materials are diverse and include the rutile, perovskite, pyrochlore, distorted fluorite, and the KSbO3-type structure. Overall, the goal of these studies is to establish a better understanding of the solid state chemistry of one of the least explored transition metals, technetium. |
