Densities of Liquid Tm₂O₃, Yb₂O₃, and Lu₂O₃ Measured by an Electrostatic Levitation Furnace Onboard the International Space Station

Liquid densities of three lanthanoid sesquioxides (Tm2O3, Yb2O3, and Lu2O3), whose melting temperatures are above 2400 °C, were measured using an electrostatic levitation furnace onboard the International Space Station (ISS). Each sample was positively charged, and its position was controlled by Coulomb forces between the sample and the surrounding electrodes. Following heating and melting of the sample by high-power lasers, its volume was calculated from its spherical shape in its liquidus phase. After weighing the mass of the sample returned to Earth, its density was determined. The densities (ρ) of Tm2O3, Yb2O3, and Lu2O3 can be expressed as ρTm2O3 = 8304 − 0.18 × (T − Tm), ρYb2O3 = 8425 − 0.55 × (T − Tm), and ρLu2O3 = 8627 − 0.43 × (T − Tm), respectively, where Tm is their melting temperatures.