Neutron powder diffraction (NPD) was carried out on the D2B diffractometer (λ=1.594 Å) at the Institute Laue Langevin (ILL). The data were analyzed with the Rietveld method using the FullProf software package Patterns were collected first at room temperature and then at successively higher temperatures in two different atmospheres, vacuum and air. For the vacuum experiment, about 2 g of powder was loaded into a vanadium can and heated using a high temperature vacuum furnace (ILL-type vacuum furnace). The furnace was pumped throughout the experiment, maintaining a vacuum of about 10 -4 bar. In air experiments, the sample was placed in a glass container and heated in an ILL furnace. Further details on the crystal structure of the stabilized phases were deposited to the ICSD database via with the following reference numbers CSD-2340066-2340075 as gathered in Table .