AgScO2 Revisited: Synthesis, Crystal Structure Refinement and Properties of the Single-phase 3R Polymorph

2011 ◽  
Vol 66 (3) ◽  
pp. 227-229 ◽  
Author(s):  
Volker Dietrich ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Activation Energy ◽  
Stainless Steel ◽  
Single Phase ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Ordered Structure ◽  
Powder Diffraction Data ◽  
X Ray ◽  
High Oxygen Pressure

Silver scandium oxide AgScO2 has been obtained from Ag2O and Sc2O3 by solid-state reaction at elevated temperature and under high oxygen pressure in stainless-steel autoclaves. AgScO2 was obtained in the 3R Delafossite-type structure, R¯3m, with a = 3.21092(2), c = 18.5398(1) Å and Z = 3, containing virtually no admixtures of the 2H polytype. The fully ordered structure was solved by high-resolution X-ray powder diffraction data, R(F2) = 0.0436, 30 parameters. AgScO2 decomposes at around 740 ºC into Ag and Sc2O3 with the release of oxygen. The conductivity of AgScO2 increases gradually with temperature from 5.79 × 10−18 to 7.94 × 10−10 S cm−1, and is ionic in nature, the activation energy for ion conduction being 75 kJ mol−1 in the temperature range from 250 to 425 ºC.

scholarly journals Synthesis and Rietveld crystal structure refinement of mackinawite, tetragonal FeS

1995 ◽  
Vol 59 (397) ◽  
pp. 677-683 ◽  
Author(s):  
A. R. Lennie ◽  
S. A. T. Redfern ◽  
P. F. Schofield ◽  
D. J. Vaughan
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Structure Refinement ◽  
X Rays ◽  
Crystal Structure Refinement ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Data Set ◽  
X Ray ◽  
Cell Parameters

AbstractMackinawite, tetragonal FeS, has been synthesised by reacting iron with Na2S solutions. A Rietveld structure refinement of X-ray powder diffraction data, recorded using X-rays monochromated from synchrotron radiation with a wavelength of 0.6023 Å, has been performed. The structure has been refined in the tetragonal space group, P4/nmm, and has the following cell parameters: a = 3.6735(4), c = 5.0328(7) Å, V = 67.914(24) Å3. Our refinement shows that the FeS4 tetrahedron in mackinawite is almost perfectly regular, with a much smaller distortion than has been previously reported. An improved X-ray diffraction data set is provided.

Polymorphs of VO(PO3)2: synthesis and crystal structure refinement revisited

2020 ◽  
Vol 235 (8-9) ◽  
pp. 303-309
Author(s):  
Sven Umlauf ◽  
Markus Weber ◽  
Robert Glaum
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Phase ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Crystal Data ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Porcelain Crucible ◽  
Silica Ampoule

AbstractThe monoclinic α-polymorph of (VIVO)(PO3)2 is obtained reproducibly by reaction of V2O5 and H3PO4 (85%) (Au crucible, 380 °C, 4 d). Its crystal structure was refined from X-ray single-crystal data [C2/c, Z = 4, a = 15.1038(7) Å, b = 4.193(2) Å, c = 9.573(9) Å, β = 126.45(3), R1 = 0.052, wR2 = 0.189 for 976 unique reflections with Fo > 4σ(Fo), 48 variables]. A single-phase powder of the β-polymorph is obtained by the reaction of V2O5, H3PO4 (85%) and oxalic acid, evaporating the mixture, and subsequent annealing (porcelain crucible, 800 °C in air, 2 d). Single crystals of β-(VIVO)(PO3)2 were grown in a sealed silica ampoule with chlorine as mineralizer. The crystal structure of the orthorhombic (pseudo-tetragonal) β-polymorph was refined from X-ray single-crystal data [pseudo-merohedral twin, Fdd2, Z = 8, a = 15.536(2) Å, b = 15.586(2) Å, c = 4.2611(5) Å, R1 = 0.032, wR2 = 0.068 for 1072 unique reflections with Fo > 4σ(Fo), 50 variables]. Earlier reports on a tetragonal polymorph with unusual geometric structure of the [(V≡O)O5] polyhedron are corrected.

Crystal structure of potassium tetraperoxomolybdate (VI) K2[Mo(O2)4]

2005 ◽  
Vol 20 (3) ◽  
pp. 203-206 ◽  
Author(s):  
M. Grzywa ◽  
M. Różycka ◽  
W. Łasocha
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Potassium tetraperoxomolybdate (VI) K2[Mo(O2)4] was prepared, and its X-ray powder diffraction pattern was recorded at low temperature (258 K). The unit cell parameters were refined to a=10.7891(2) Å, α=64.925(3)°, space group R−3c (167), Z=6. The compound is isostructural with potassium tetraperoxotungstate (VI) K2[W(O2)4] (Stomberg, 1988). The sample of K2[Mo(O2)4] was characterized by analytical investigations, and the results of crystal structure refinement by Rietveld method are presented; final RP and RWP are 9.79% and 12.37%, respectively.

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