The Use of Ternary Cations to Control Nucleation: Avoiding Binary Compounds as Reaction Intermediates

In this article we compare and contrast the evolution of ternary modulated reactants of the form M−Mo−Se (M = Ni, Zn, Sn, In, and Cu) with each other and with the binary Mo−Se system. The binary elementally modulated reactants interfacially nucleate MoSe 2 over a broad composition range surrounding that of the binary compound Mo 6 Se 8 . Increasing the concentration of any of the studied ternary elements except nickel above a critical value in the initial reactant suppressed interfacial nucleation of the diselenide. The nickel-containing reactants all interfacially nucleated Ni x MoSe 2 at low temperatures. The subsequent nucleation and growth of crystalline compounds from the amorphous intermediates obtained in the other four systems was found to depend on both the identity and concentration of the ternary element. In the Sn−Mo−Se system, a layered dichalcogenide was the first compound nucleated. In the Zn−Mo−Se system, the dichalcogenide and the ternary compound Zn x Mo 6 Se 8 were observed to nucleate at approximately the same temperature. In the copper- and indium-containing systems, the cluster-containing compounds, Cu x Mo 6 Se 8 and In 3.33 ±δ Mo 15 Se 19, were observed to be the first crystalline compounds formed. Annealing all four of these systems at temperatures greater than 1100 °C resulted in the growth of Chevrel phase compounds at the expense of molybdenum diselenide.