A combined experimental and theoretical study of enthalpy of phase transition and fusion of yttria above 2000 °C using “drop-n-catch” calorimetry and first-principles calculation

“Drop-n-catch” calorimetry was performed on Y₂O₃ spheroids of 2–3 mm in diameter, prepared by laser melting of powders. Samples were aerodynamically levitated in a splittable nozzle levitator in air or argon flow, laser heated from ∼2200 to 3000 °C and dropped into a calorimeter at 25 °C, thus measuring their enthalpy as a function of temperature. The fusion enthalpy of cubic Y₂O₃ was derived from the step in the temperature–enthalpy curve as 119 ± 10 kJ/mol. Calculations performed using density functional theory and molecular dynamics techniques produced the value 127 ± 3 kJ/mol Y₂O₃. This combined methodology enables accurate determination of the enthalpies of fusion and phase transition of refractory oxides, including those containing lanthanides and actinides.