Exploratory synthesis of quaternary rare earth transition metal aluminum tetrelides: Utilizing molten aluminum as a solvent

Metallic fluxes have recently emerged as an important synthetic tool in solid state chemistry for both crystal growth studies and exploratory studies of new chemical systems. Our research group is currently employing Al metal fluxes to study quaternary intermetallics in the RE/M/Al/Tt systems (RE = rare earth, M = transition metal, Tt = Si or Ge) in the hopes of discovering new structural relations and interesting physical properties.; We have discovered that by utilizing Al fluxes a wide variety of products with novel structures and compositions including RE2Ni(Ni xSi1-x)Al4Si6, RE2NiAl 4Ge2, RENiAl4Ge2, RE1-x M2Al5-ySiy, RE2-x M2Al4Tt2(Al1-yTt y)(Al1-zTtz)2, RE4Fe 2+xAl7-xSi8, REFe4Al9Si 6 and RE8Ru12Al49Si9(Al xSi12-x)can be produced. Along with the new structure types, several isostructural analogues of known compounds such as RENiAl 4(Si2-xNix) and RENiAl6-xGe 4-y have been synthesized for the first time.; In addition to exhibiting interesting structures, the compounds have displayed several unusual physical properties such as valence fluctuations, metamagnetic phase transitions, and orientation dependent magnetism. Of particular interest, however, is the apparent filling of the transition metal d bands in the systems. This unexpected behavior appears to be caused by electron transfer from the more electropositive RE and Al atoms to the less electropositive transition metals.; This dissertation presents the synthesis, structural relationships, characterization and properties of the newly discovered compounds. The synthetic work performed here provides the groundwork for further exploration of these and related systems.