LaMg11 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 LaMg12−x intermetallic at 500 °C. During a vacuum thermal desorption from the LaH3–MgH2 nanocomposite prepared by reactive ball milling in H2, hydrogen desorption from the La dihydride occurred via a mechanism of cooperative phase transformation at temperatures being 400° lower than the desorption from pure LaH2. The crystal structure of the intermetallic was determined by synchrotron X-ray diffraction (SR XRD). The orthorhombic LaMg12−x has a giant unit cell, the volume of which exceeds 8000 A3. In situ SR XRD studies showed the fine details of the hydrogen desorption process with several parallel and consecutive transformation steps.