Sublimation and condensed phase thermodynamics of tetrakis (2,2,6,6-tetramethyl-3,5-heptanedionato)cerium(IV) as a volatile precursor for ceria-based materials

The actively developing gas-phase deposition (MOCVD, ALD etc.) of ceria-containing multicomponent coatings has been demanding precursors with properly defined thermal properties since their volatilization thermodynamics as well as condensed phase behavior is highly answerable for the chemical composition of a target material. Herein, we present a thermal study of tetrakis (2,2,6,6-tetramethyl-3,5-heptandionato)cerium(IV) which is a convenient precursor for materials based on cerium oxide. The complex has been synthesized, purified and identified for thermodynamic study. Saturated vapor pressure over the solid compound was measured by a flow method in the temperature range from 430 to 468 K. Thermodynamic characteristics of enthalpy and entropy of sublimation process at average temperature has been calculated from the experimental data. Differential scanning calorimetry has been applied to measure the melting temperature and enthalpy as well as heat capacity in the temperature range from 306 to 459 K. Combining calorimetric and vapor pressure data with empirical approach, enthalpy and entropy of sublimation have been referred to 298.15 K and vapor pressure temperature dependence operating over a wide temperature range has been derived. This benefit of extrapolation of vapor pressure values to required temperatures could be used to define precisely the temperature regimes of film deposition by gas-phase processes involving tetrakis (2,2,6,6-tetramethyl-3,5-heptandionato)cerium(IV) as precursor.