Two high-pressure tungsten oxide structures of W₃O₈ stoichiometry deduced from high-resolution electron microscopy images

A New High-Pressure Modification of Nb2O5

“…The oxygen arrangement within these layers is very similar to that in another high-pressure phase, namely W O (I) (Fig. 6b), as may be seen from the oxygens in or near the plane containing tungsten (6). Then, as a consequence of the C-centering in Z-Nb O , the niobium atoms (at y"0 and 0.5) are coordinated by four oxygens in or near one plane above and by three oxygens in or near a parallel plane below, giving an irregular coordination of seven oxygens around niobium (Fig.…”

Structures and phase transitions of B-Ta2O5 and Z-Ta2O5: two high-pressure forms of Ta2O5

“…W 3 O 8 , for example, forms two high-pressure phases of the same stoichiometry, W 3 O 8 (I) and W 3 O 8 (II). The structure of W 3 O 8 (I), which is more dense, was observed to form domains within the W 3 O 8 (II) regions (Sundberg et al, 1993). It is interesting to note that the oxygen arrangements parallel to (010) in Z-Ta 2 O 5 and Z-Nb 2 O 5 are almost identical and very similar to a part of that in W 3 O 8 (I).…”

Structure and Thermal Stability of La0.10WO3+y; A Hexagonal Tungsten Bronze Related Phase Formed at High Pressure

“…According to the X-ray patterns, the samples prepared at 50 kbar (hp2) and 80 kbar (hp3) consisted of approximately 90 wt% of the HTB-related compound. A small amount of WO seemed also to be present in hp2, whereas hp3, prepared at the highest pressure, contained some of the high-pressure oxide, W O (II) (20). The X-ray powder pattern of La WO (ap sample) showed lines characteristic of a perovskite tungsten bronze (PTB) with cubic symmetry (a"3.840 A > ).…”