Phase Relations in the Al2O3-V2O5-MoO3 System in the Solid State. The Crystal Structure of AlVO4

Abstract

Phase relations in the ternary oxide system Al 2 O 3 -V 2 O 5 -MoO 3 in the solid state in air have been investigated by using the x-ray diffraction (XRD) and differential thermal analysis/thermogravimetric (DTA/TG) methods. It was confirmed that in the subsolidus area of the Al 2 O 3 -V 2 O 5 -MoO 3 system, there exist seven phases, that is Al 2 O 3 , V 2 O 5(s.s.) , MoO 3 , AlVO 4 , Al 2 (MoO 4 ) 3 , AlVMoO 7 , and V 9 Mo 6 O 40 . Seven fields, in which particular phases coexist at equilibrium, were isolated. The crystal structure of AlVO 4 has been refined from x-ray powder diffraction data. Its space group is triclinic, P " 1, Z = 6, with a = 0.65323 (1) nm, b = 0.77498(2) nm, c = 0.91233(3) nm, a = 96.175(2)°, b = 107.234(3)°, c = 101.404(3)°, V = 0.42555 nm 3 . The crystal structure of the compound is isotypic with FeVO 4 . Infrared (IR) spectra of AlVO 4 and FeVO 4 are compared.

Phases in the subsolidus area of the system CuO–V2O5–Fe2O3

“…IR spectrum of H-type phase (curve a) is very similar to IR spectra of the other phases with such structure [21,22]. According to the literature data relating to the H-type phase structure [10], the absorption bands recorded in the wave-number range 1,070-540 cm -1 can be most likely ascribed to stretching vibrations of the V-O bonds in the VO 4 tetrahedra [23][24][25]. The absorption bands located in the remaining wavenumber range can be due to the stretching vibrations of M-O bonds in the FeO 6 [27].…”

Synthesis and selected properties of a new solid solution in the Zn2FeV3O11–Mg2FeV3O11 system

“…At this wave number range one can expect the occurrence of absorption bands related with stretching vibrations of V-O bonds in highly distorted VO 4 and VO 5 polyhedra [5,9,[21][22][23]. A shoulder at 1,010 cm -1 most probably can be ascribed to stretching vibration of the shortest V-O bond in VO 5 trigonal bipyramids characteristic for crystal structure of both Zn 2 FeV 3 O 11 and Mg 2 FeV 3 O 11 [9,21].…”

“…It has two maxima at 744 and 650 cm -1 and two shoulders at 822 and 570 cm -1 . Band lying within the wave number range of 920-600 cm -1 may be related with the stretching vibrations in moderately distorted VO 4 tetrahedra [5,[21][22][23]. On the other hand, absorption bands below 600 cm can be ascribed to stretching vibrations in ZnO x , MgO x , and FeO x polyhedra and to bending vibrations in VO x polyhedra [5,9,20,[22][23][24].…”

Oxidation behaviour of Mo–Si–B–(Al, Ce) ultrafine-eutectic dendrite composites in the temperature range of 500–700 °C

“…Therefore, the kinetics of MoO 3 formation and its permeation through the scale becomes sluggish resulting in a lower rate of mass loss of 5.58/6.19 mg cm À2 h À1 in MSBA/MSBACe. According to the Al 2 O 3 eMoO 3 phase diagram [47], only w10 mol% Al 2 O 3 is required to form Al 2 (MoO 4 ) 3 through a eutectic reaction at temperatures close to 700 C. Examination of the microscopic features on the top of the outer most layer of the Al containing alloys has shown the evidence of melting (inset in Fig. 4 (d)).…”