Measurements of Vapor Pressures of Sc,La, and Ce by Multi-Knudsen Cell Mass Spectrometry

The vapor pressures of Sc, La, and Ce were determined by multi-Knudsen cell mass spectrometry with ionized cross sections as described in the literature. The vapor pressure of Sc at temperatures from 1373 K to 1573 K was measured using Cu as a reference material, and those of La and Ce from 1473 K to 1573 K were measured using Y as a reference material. From the measured vapor pressures, the Gibbs energy of formation of each gaseous element was derived.