LaMg 11 with a giant unit cell synthesized by hydrogen metallurgy: Crystal structure and hydrogenation behavior

Abstract

We have successfully applied a hydrogen metallurgy synthesis to yield LaMg 12− x intermetallic at 500 °C. During a vacuum thermal desorption from the LaH 3–MgH 2 nanocomposite prepared by reactive ball milling in H 2, hydrogen desorption from the La dihydride occurred via a mechanism of cooperative phase transformation at temperatures being 400° lower than the desorption from pure LaH 2. The crystal structure of the intermetallic was determined by synchrotron X-ray diffraction (SR XRD). The orthorhombic LaMg 12− x has a giant unit cell, the volume of which exceeds 8000 Å 3. In situ SR XRD studies showed the fine details of the hydrogen desorption process with several parallel and consecutive transformation steps.