Supersaturation and optical properties of metal-rich ZrO and ZrN liquids

The effects of oxygen and nitrogen additions on the optical properties of pure liquid zirconium were investigated under containerless conditions using rotating analyzer ellipsometry. Liquid zirconium was electromagnetically levitated and melted, and metered flows of oxygen and nitrogen were added to the melt in separate experiments. The optical constants (n and k) and the normal spectral emissivity (ελ) of the liquid at λ = 633 nm were measured over the duration of the experiments. The measured values of n and k decreased and ελ increased with the O and N concentrations for the single-phase liquids. Metastable ZrO solutions with 135% of the liquidus O-atom concentration were achieved at a temperature of 2260 K. Precipitation of a solid phase from the ZrN liquid at 2290 K occurred at a concentration of 7.6 at.% N. Based on these results, a new method using in situ ellipsometric measurements is described for the accurate determination of liquidus concentrations and temperatures. Dissolved oxygen and nitrogen were found to influence the optical properties of liquid zirconium in a manner proportional to their respective valences.