Friday Synthesis Symposium
Reactive Flux Synthesis of Metal Chalcoborates and Chalcophosphates
Presented by Daniel Chica (Roy Group)
Abstract:
The ceramic method has been a popular technique for the synthesis of solid state materials due to its simplicity. However, these reactions can take weeks to months to achieve phase purity and the resulting material is typically polycrystalline. Relatively high temperatures are needed to overcome the large energy barrier of solid state diffusion which limit the products formed to thermodynamic phases. An alternative route employed by solid state chemists is the flux method, a process where the precursors are dissolved in a solution(flux) at moderate temperatures and the phase of interest crystallizes from the flux as the temperature is lowered. Because these reactions occur in the liquid phase, the orders of magnitude increase in diffusion significantly reduces reaction times while promoting large crystallite size. In addition, these lower temperature regimes enable kinetic phases to be stabilized. In the first part of the talk, I will describe the use of the flux method for the synthesis of the framework compound Sn4B12Se12. Reaction of this compound with molten sulfur or tellurium led to an anion-exchanged or tellurium intercalated phase, respectively. In the second part of the talk, I will discuss the development of the P2S5 flux method for the rapid synthesis and crystal growth of several metal thiophosphates.
