Differential thermal analysis of hydrogen-induced amorphization in C15 Laves compounds RCo 2

Abstract

Structural changes of the C15 Laves compounds RCo 2 (Rrare earth metals) during differential thermal analysis (DTA) in a hydrogen atmosphere have been investigated by X-ray diffractometry, transmission electron microscopy and differential scanning calorimetry. The results of TbCo 2 and CeCo 2 are exemplified. The DTA curves of the RCo 2 compounds exhibit three or four exothermic peaks resulting from hydrogen absorption, hydrogen-induced amorphization, crystallization and grain growth. As the atomic number of R increases, the amorphization temperature T a increases, but the ratio T a/ T m, where T m is the melting point of the original compound, is nearly constant at 0.4. The mechanisms of hydrogen-induced amorphization in the RCo 2 compounds is discussed.