Iron-promoted phases in the tungsten-oxygen system

Investigations of Nonstoichiometric Tungsten Oxide Nanoparticles

“…No evidence for the existence of this phase in the encapsulated nanowhiskers was found in the previous study (5). Furthermore, a W O phase, which consists of PC and HC is known as well (11) and is schematically represented in Fig. 2d ([010] projection) .…”

High‐Throughput Screening of Thin‐Film Semiconductor Material Libraries II: Characterization of FeWO Libraries

“…From about 11 at %F eo nwards, these peaks disappear and the main phase changes to W 5 O 14 ,w hich has ad istinct (001) reflection.T his MagnØli phase was reported by McColm et al to be at etragonal( tp152)s tructure with an oxygen-to-metal ratio of 2.8, which is stabilized by the existence of small amountso fF ea toms. [21] Although the amount of Fe is much lower for the reported bulk diffusion samples than for the sputter-deposited samples, the XRD data clearly point to the existence of the W 5 O 14 phase, especially for sam- www.chemsuschem.org ples from ML3 (Figure 2c). Nevertheless the WO 3 and the W 5 O 14 phases are likely to co-exist over al arge compositional range, where the more pronounced XRD signals are covering the less pronounced signals of the other phase, especially in the range between 11 and 15 at %F e. Starting at about 20 at % Fe, the W 5 O 14 peak intensity is decreasing again and disappears at around 27 -29at% Fe.…”

Spark Plasma Sintering of Tungsten Oxides WOx (2.50 ≤ x ≤ 3): Phase Analysis and Thermoelectric Properties

“…The reflection positions of "WO 2.82 " in the synchrotron pattern of a two-phase W 18 O 49 /"WO 2.82 " sample somewhat fit the PC phase W 12 O 34 (x = 2.83) with slightly changed lattice parameters. The synthesis as single-phase material and structure refinement still failed, which indicates that the phase is metastable and its structure needs to be further analyzed.…”

“…According to powder X-ray diffraction (PXRD), a new phase termed as "WO 2.82 " is observed in the composition range 2.72 ≤ x ≤ 2.90 in addition to the expected pentagonal column (PC) phase W 18 O 49 (x = 2.72) and crystallographic shear (CS) plane phase W 20 O 58 (x = 2.90). The reflection positions of "WO 2.82 " in the synchrotron pattern of a two-phase W 18 O 49 /"WO 2.82 " sample somewhat fit the PC phase W 12 O 34 (x = 2.83) with slightly changed lattice parameters.…”

“…CS plane structures occur when a transition metal is partially reduced and oxygen layers are removed from the structure, e.g., of TiO 2 , VO 2 , MoO 3 and WO 3 . In the tungsten-oxygen system ( Figure 1a) with decreasing O/W-ratio x the observed phases are the insulating ReO 3 -type WO 3 , the semiconducting phase W 20 O 58 with CS planes, the metallic phase W 18 O 49 with pentagonal columns (PC) and the The vapor-transport preparation route to obtain these phases comprises a high-temperature heating of WOx powder mixtures over several days and weeks [14,15,[21][22][23]. Recently WO2.72 (W18O49) and WO2.90 (W20O58) were successfully prepared by spark plasma sintering (SPS) being promising bulk TE materials [11,12,24].…”