New equilibrium phase in the Fe–Ge system obtained by mechanical alloying

Crystal Growth of the Nowotny Chimney Ladder Phase Fe2Ge3: Exploring New Fe-Based Narrow-Gap Semiconductor with Promising Thermoelectric Performance

“…However, neither the Rietveld refinement nor the proper indexing of the diffraction pattern was performed. 20 Later, Li et al 21 performed transmission electron microscopy study on a sample prepared under the same conditions and found indications of an incommensurately modulated Nowotny chimney ladder structure with the composition FeGe γ deviating from the stoichiometric one with γ = 1.5. This incommensurability of the crystal structure presumably leads to a glass-like behavior characterized by the low thermal conductivity at high temperatures as proposed in a recent study by Sato et al, who established FeGe γ as a promising thermoelectric material with the large power factor of 1.9 mW m -1 K -2 and the dimensionless figureof-merit of 0.57 near 600 K. 22 Herein, we put forward a synthetic approach based on chemical transport reactions that enables us to overcome the kinetic passivity of Fe and Ge at low temperatures and to obtain high-quality polycrystalline samples as well as single crystals of the Nowotny chimney ladder phase Fe 2 Ge 3 .…”

“…Recently, a new NCL compound was discovered in the binary system Fe-Ge. 20 This compound is thermodynamically stable only at relatively low temperatures below ca. 600 °C and remains hidden due to the kinetic inertness of iron and germanium at such temperatures.…”

Synthesis and Thermal Stability of B20-Type TMGe (TM = Mn, Fe and Co) Intermetallic Compounds Prepared by Mechanical Milling

“…Such increases are not observed clearly for the MnGe and CoGe powders under our heat-treatment conditions. The difference may result from their thermal stability; according to the TMGe binary phase diagrams, 22,23) only the FeGe B20-phase is thermodynamically stable up to 903 K, i.e., stable MnGe and CoGe B20-phases are not reported at ambient pressure. Therefore, our method can produce metastable B20-phases at ambient pressure without a HPHT synthesis.…”

Growth of epitaxial FeGeγ nanocrystals with incommensurate Nowotny chimney-ladder phase on Si substrate

“…This lattice parameter was slightly smaller than the reported parameter (8.92 Å). 24) This value cannot be explained by the other Fe-Ge compounds. In the another report, 26) the lattice parameter of c-axis of Fe subcell, which can be lattice parameter of crystal structure along c-axis, was reported to be 8.2 Å, which was consistent with our study.…”