Mass-Spectrometric Study of the Yttrium—Carbon System

A high-temperature investigation of the vapor in thermodynamic equilibrium with Y–C condensed system was carried out in the temperature range 2075°—2340°K. Y and YC2 are shown to be important species in the vapor phase. Utilizing the pressure-independent reaction Y(g)+2C(s)→YC2(g), second- and third-law methods yielded D00=155±6 kcal mole−1 and D00=156±5 kcal mole−1, respectively, for the Y–C2 bond energy. An estimated heat of formation ΔH°f298=−27±6 kcal mole−1 for solid dicarbide is also obtained. Comparison between Me—C2 and Me—O bond strengths is made for Group IIIA elements and for the first two elements of the lanthanide series.