Crystal Structure Analysis and Phase Transition in Lead Orthovanadate Pb₃(VO₄)₂

High-temperature breakdown of the synthetic iodine analogue of vanadinite, Pb5(VO4)3I: an apatite-related compound for iodine radioisotope immobilization?

“…The starting model for the iodovanadinite was taken from Audubert et al (1999) with space group P6 3 /m and a shifted Chebyshev function was used to fit the background. The b-lead-orthovanadate, space group P2 1 /c (Kasatani et al, 1992) was fitted to the data below 360 K and g-lead-orthovanadate, space group R3m (Kiat et al, 1991) above 360 K as lead orthovanadate undergoes a phase transition to the g-form at~357 K (Kuok et al, 1989).…”

Monoclinic sphere packings. III. Trivariant lattice complexes of P2/c and P21/c

“…(iii) It is noticeable that in many cases the centres of complex anions are arranged according to a diamond-like (4/6/c1, dia) configuration. This holds, for instance, for the SO 4 tetrahedra in Fe(OH)SO 4 (P2 1 /c, Ventruti et al, 2005), in SnSO 4 at 0.2 GPa (P2 1 /c, Hinrichsen et al, 2008) and in Cd(SO 4 ) 2 (HgO) 2 H 2 O (P2/c, Weil, 2004), the VO 4 tetrahedra in Pb 3 (VO 4 ) 2 (P2 1 /c, Kasatani et al, 1992), the BF 3 (H 2 O) tetrahedra in BF 3 (H 2 O) 2 (P2 1 /c, Bang & Carpenter, 1964), the AlCl 4 tetrahedra in GaAlCl 4 (P2 1 /c, Staffel & Meyer, 1987), the ReO 4 tetrahedra in LiReO 4 (H 2 O) (P2 1 /c, Abakumov et al, 2001), the SO 3 groups in Cu 2 Zn(SO 3 ) 2 (H 2 O) 2 (P2 1 /c, Sghyar et al, 1984) and the SeO 3 groups in Cu 2 O(SeO 3 ) (P2 1 /c, Effenberger & Pertlik, 1986). Such an arrangement provides large cavities for the rest of the structure and can be easily adapted to the required space.…”

High-Temperature Transformations in Calcium Orthovanadate Studied with Raman Scattering

“…The results of this study should be compared with what is known about phase transitions in other compounds with the palmierite-type structure. ,,− Such a comparison should serve as an indirect source of information on the nature and mechanism of the phasetransitions in Ca 3 (VO 4 ) 2 . It is especially important for the case of Raman spectroscopy, which is quite sensitive to probe the transformations of the internal modes of molecular ions but does not provide sufficient information on the lattice oscillations.…”

“…It is especially important for the case of Raman spectroscopy, which is quite sensitive to probe the transformations of the internal modes of molecular ions but does not provide sufficient information on the lattice oscillations. For that instance, the high temperature γ form of Pb 3 (VO 4 ) 2 ( R 3̄ m ) transforms into two monoclinic ferroelastic β ( P 2 1 / c space group) and ferroelectric α ( A 2 space group) phases at 373 and 273 K, respectively. , Through these transitions, associated with strong volumetric discontinuities, the VO 4 3- tetrahedra remain rigid and the interlayer Pb (2) atoms are shifted from their ideal positions ( C 3 v ) to accommodate the steric effects due to a changing delocalization of their electronic lone pairs .…”

“…For that instance, the high temperature γ form of Pb 3 (VO 4 ) 2 (R3 hm) transforms into two monoclinic ferroelastic β (P2 1 /c space group) and ferroelectric R (A 2 space group) phases at 373 and 273 K, respectively. 36,37 Through these transitions, associated with strong volumetric discontinuities, the VO 4 3tetrahedra remain rigid and the interlayer Pb (2) atoms are shifted from their ideal positions (C 3v ) to accommodate the steric effects due to a changing delocalization of their electronic lone pairs. 36 However, no soft mode, associated with these structural changes, was detected in a Raman study.…”