Crystal Growth of Intermetallics from the Joint Flux: Exploratory Synthesis through the Control of Valence Electron Count

Abstract

In this study, we modify the flux-growth method for the purpose of exploratory synthesis of ternary intermetallic compounds. Our concept is based on the assumption that valence electron count plays a crucial role in the stability of polar intermetallic compounds of different structure types. Control of the valence electron count parameter is made possible through the use of an excess of two metals having a different number of valence electrons. By gradually changing the ratio between these metals in the joint flux, we scan the gross number of valence electrons and explore the crystallization of new compounds. In the ternary system Re−Ga−Zn, we detect compounds belonging to three structure types, ReGa 5 , PtHg 4 , and V 8 Ga 41 , while gradually increasing the content of Zn metal in the flux. Two new compounds, ReGa 3 Zn and Re 8 Ga 41−x Zn x with x = 21.2(5), are obtained in the form of high-quality single crystals, and the former compound shows the narrow-gap semiconducting behavior favorable for high thermoelectric performance.

Superconductivity in the Endohedral Ga Cluster Compound PdGa5

“…Relationship between the T c and valence electron count in endohedral gallide superconductors. Within the Mo 8 Ga 41 family, the VEC was changed by partial substitution in both Mo (with V) , and Ga sites (with Sn and Zn). − The Mo 4 Ga 21 family consists of five reported members with Ga partially substituted by chalcogens, Sn, or Sb. , In panel (a), the total number of valence electrons is divided by the number of transition metal atoms (VEC/TM atom, as was proposed by Xie et al .) .…”

“…Endohedral Ga cluster compounds constitute a family of superconductors that recently gained increased attention. − While crystal structures found in the TM x Ga y (TM, transition metal) compounds are diverse and rather complex, they can be conveniently described as networks of interconnected endohedral Ga clusters. Xie et al .…”

Endohedral Cluster Superconductors in the Mo–Ga–Sn System Explored by the Joint Flux Technique

“…In our recent study, we proposed a combination of aliovalent metals to control the gross valence electron count in order to perform exploratory synthesis in a ternary system containing a transition metal and two low-melting nontransition metals. Within the flux-growth method, the two aliovalent metals can be taken in excess and facilitate crystal growth of transition-metal-based intermetallic compounds.…”

“…It may also be interesting from a more fundamental viewpoint, because at least Mo 8 Ga 41 reveals several features incompatible with the standard Bardeen−Cooper−Schrieffer (BCS) model: strong electron−phonon coupling in the superconducting state 12 as well as signatures of multigap superconductivity. 13−15 In our recent study, 16 we proposed a combination of aliovalent metals to control the gross valence electron count in order to perform exploratory synthesis in a ternary system containing a transition metal and two low-melting nontransition metals. Within the flux-growth method, the two aliovalent metals can be taken in excess and facilitate crystal growth of transition-metal-based intermetallic compounds.…”

Family of Mo4Ga21-Based Superconductors

“…(2), (3), and (4) can be synthesized exactly from the stoichiometric mixtures, while in the case of E = S, the x = 0.5 and x = 0.75 starting compositions yield phase-pure samples (see Table S1 of Supporting Information). The crystal growth can be performed using the joint flux technique . For example, the Mo­(Ga 1– y Te y ) 50 sample with the joint excess of Ga and Te can be annealed at a high temperature of 1000 °C and slowly cooled down, yielding large bulky crystals of GaTe and small needle-like single crystals of (3) for y = 0.05.…”