Complex Carbides, Nitrides and Hydrides Grown from Highly Reducing AE/Li Flux Mixtures (AE = Ca, Yb)

Flux synthesis of new complex compounds uses an excess of molten metals or salts as a reaction medium. This solution-based method is a valuable tool in materials synthesis, enabling the solid-state chemist to achieve reactivity at relatively low temperatures compared to traditional solid-state reactions. A growing effort in the field of flux synthetic chemistry is to enable the directed synthesis of materials. This entails being able to predict products that will form, or at least the building blocks that will be incorporated into the products. It is therefore necessary to explore various flux systems in order to develop trends that will better help chemists understand the mechanisms by which compounds and their building blocks form. To this end, two flux mixtures, Ca/Li and Yb/Li, were explored and several new complex compounds were discovered which feature a range of structural and electronic properties. Calcium and ytterbium commonly form solid solutions in compounds due to similarities in their ionic radii and valence. Calcium melts above 800°C, but the addition of lithium lowers this melting point drastically to around 300°C. Unfortunately, there is no phase diagram for mixtures of ytterbium and lithium, so attempts to grow new crystals in this melt was largely speculative on the basis that ytterbium may behave similarly to calcium and produce a low-temperature solution when mixed with sufficient lithium. This is supported by the fact that ytterbium has a similar melting point to calcium, and binary phase diagrams incorporating ytterbium or calcium mixed with other metals feature similar trends. Ca/Li flux is able to dissolve refractory elements such as carbon, as well as salts such as Ca3N2 and CaH2. New carbide and hydride compounds formed from Yb/Li flux suggest similar capabilities, however reactivity with nitride salts is still undetermined. Electropositive fluxes in general are useful solvents for the growth of new complex carbides, nitrides and hydrides. Compounds containing these light elements are extremely important for many industrial applications. Therefore, further exploration into making new complex compounds incorporating them is merited. Several new compounds including Ca12InC13-x, Ca6Te3N2, Ca6(LixFe1-x)Te2N3, Ca8In2SiN4, Ca3SiN3H, and Yb~51In13H27 were synthesized from either Ca/Li or Yb/Li flux mixtures. Their synthesis, structural and electronic properties, as well as potential applications are discussed herein.