Thermodynamics of the production of condensed phases in the chemical vapor deposition process of zirconium diboride with ZrCl ₄-BCl ₃-H ₂ precursors

Production conditions of ZrB ₂, Zr and B condensed phases in the chemical vapor deposition process of ZrCl ₄-BCl ₃-H ₂ precursors have been investigated in details based on the thermodynamic analyses using the FactSage code and 41 species being involved from its embedded database. The production of the condensed phases has been examined as a function of the injected reactant ratios of ZrCl ₄/(ZrCl ₄ + BCl ₃) and H ₂/(ZrCl ₄ + BCl ₃), temperature and pressure. The results show that the condensed phase composition is quite sensitive to the reactant ratios and to the temperature whereas it is insensitive to the pressure. The ideal conditions for the deposition of ZrB ₂ are as follows: temperature ranging from 1050 to 1550 K, ratios of ZrCl ₄/BCl ₃ of 1/2 and of H ₂/(ZrCl ₄ + BCl ₃) in the range of 10-10 ¹⁰, and pressures lower than 10.1 kPa. The production of zirconium form in the region of H ₂/(ZrCl ₄ + BCl ₃) from 10 ³ to 10 ¹⁴ with ZrCl ₄/BCl ₃ ratio higher than 1/2 and free boron appears in the ratios of H ₂/(ZrCl ₄ + BCl ₃) from 10 ^{- 2} to 10 ⁵ with ZrCl ₄/BCl ₃ ratio lower than 1/2. The deposition of single-phase ZrB ₂ and the co-deposition of ZrB ₂ with Zr or ZrB ₂ with B would be easily controlled by changing the ratios of ZrCl ₄/BCl ₃ and H ₂/(ZrCl ₄ + BCl ₃). In addition, the concentration distribution of precursors and gaseous species in the system was investigated. The results in this work are consistent with the available experimental and theoretical ones, and will be helpful for further experimental investigation of different deposition conditions with respect to the ratio of the injected reactants, pressure and temperature.