A Combined Experimental and Theoretical Study on the Formation of Crystalline Vanadium Nitride (VIM) in Low Temperature through a Fully Solid-State Synthesis Route

摘要

An efficient method of synthesis of the vanadium nitride (VN) at low temperature is evaluated, and a mechanism for the crystallization process is proposed in this paper. From the mixture of ammonium m-vanadate with guanidinium carbonate an intermediate, guanidinium m-vanadate (GmV), is produced. GmV decomposed and underwent interesting structural transformations with increasing temperatures. This process is studied by theoretical (periodic DFT calculations) and experimental (~(51)V MAS NMR, XRD, FTIR, and elemental analysis) methods. It is proposed that GmV is first decomposed into reactive species, then through solid-state transformations it is converted into vanadium oxynitride (VO_xN_(1-x)) with varying stoichiometry, and, last, GmV transforms itself into crystalline NaCl-type structure vanadium nitride. The DFT calculations show that this transformation is energetically favorable, and the formation of a VO_xN_(1-x) solid solution is feasible.