Fig. 2.
Powder x-ray diffraction patterns of FeSe0.82 and FeSe0.88. The patterns show that the resulting sample with starting composition of Fe (53%)/Se (47%) composes of primarily PbO-type tetragonal FeSe1−x (P4/nmm), the α-phase, and partly of NiAs-type hexagonal FeSe (P63/mmc), the β-phase. The sample with higher initial iron content, Fe (55%)/Se (45%), shows no β-phase but trace amounts of possible impurity phases including elemental selenium, iron oxide, and iron silicide (marked with an asterisk). Question marks in the figure represent unknown phases.