Various Methods of Synthesis and Analysis of Undiscovered Zintl Phases

• Daniel Tortorella, Chemical Engineering, University of Delaware

• Svilen Bobev, Chemistry and Biochemistry, University of Delaware

With the rise of interest in thermoelectric materials in recent years, a specific category of intermetallic phase has risen in interest over the past few decades: the Zintl phase. These compounds are the result of a ternary reaction involving an alkali metal, an alkaline earth metal, and a third metal which can vary from a post-transition metal, a semi-metal, or a nonmetal. Multiple different methods are employed to create these phases, such as a flux reaction, where an excess of a low-melting metal is employed to act as a “solvent” for the metals. Another common method is via a direct reaction where the components are sealed within a niobium vessel and then heated. The crystals produced by these reactions are then analyzed via x-ray diffraction, both analyzing a pulverized powder of the sample and a singular crystal. The diffraction allows one to determine known phases in the product and the size and shape of the unit cell, the crystal’s repeating building block, of the sample. Knowledge of these two parameters allows one to solve the structure of the crystal and determine and exact locations and arrangement of the crystal’s atoms.