Thermodynamic Evaluation of Chemical Transport of VSe2 and ZrSe2 with Сl2 and I2 as Transporting Agents

To study chemical transport and refine synthetic routes, single crystals of vanadium and zirconium diselenides were grown by the chemical transport reaction method using I2 and Cl2 as transporting agents. The thermodynamic parameters of chemical transport have been evaluated, and the mass transfer direction in a growth ampoule has been determined. The phase composition of the samples has been examined by X‑ray powder diffraction. Analysis of X-ray powder diffraction patterns of samples from the low- and high-temperature zones of the growth ampoule has confirmed the predictions based on thermodynamic calculations. With both transporting agents, ZrSe2 transport occurs from the cold to the hot zone of the ampoule, while the direction of VSe2 transport depends on the nature of the transporting agent. With I2 as a transporting agent, transport occurs from the hot to the cold zone of the ampoule, while with Cl2, in the opposite mass transfer direction is observed. Microphotographs of the samples are consistent with thermodynamic and X‑ray diffraction data. The results can be used to optimize the technology of producing layered transition metal dichalcogenides.