Complex Distribution of Diphosphate Groups in the Structure of V(IV) Phosphates A(VO)₃(P₂O₇)₂ (A = Sr, Pb, and Ba)

Abstract

New V(IV) diphosphates A(VO) 3 (P 2 O 7 ) 2 have been synthesized for A ) Ba, Sr, and Pb. Their X-ray diffraction and electron microscopy studies show their complex crystal chemistry. The polycrystalline samples of the Ba, Sr, and Pb phases and the single crystals of Sr and Pb phases exhibit a P2 1 2 1 2 1 -type structure (called R form) similar to that observed for K(VO) 3 -(P 2 O 7 ) 2 . For a single crystal of Ba(VO) 3 (P 2 O 7 ) 2 , a new structural form, called , has been stabilized. It crystallizes in the P11b space group, with cell parameters similar to those of the R form. This structure, closely related to that of the R form, differs from the latter by the distribution of the barium cations and the surrounding P 2 O 7 groups. The HREM study of polycrystalline -Ba(VO) 3 (P 2 O 7 ) 2 shows the great flexibility of this structure. It demonstrates the coexistence of the two structures, P2 1 2 1 2 1 and P11b, in many crystallites, in the form of P11b intergrowth defects in the P2 1 2 1 2 1 matrix.

A Vanadium(IV) Diphosphate with an Intersecting Tunnel Structure, PbVOP2O7

“…This is the case with the monophosphate hydrates Pb(VOPO ) )4H O which exhibit di!erent forms of layered structures (1,2), with the hydroxide monophosphate Pb(OH)V(HPO ) (3), and with several anhydrous monophosphates Pb (VO \V P V )O (4), PVO PO (5), Pb(VO) (PO ) (6), and Pb V VO(PO ) (7). In contrast, only two lead vanadodiphosphates are actually known, PbV (P O ) (8) and Pb(VO) (P O ) (9). This study is devoted to the crystal growth and the structure determination of a novel vanadium(IV) diphosphate, PbVOP O , built up of octahedral [VO ] chains interconnected through P O group, forming intersecting tunnels.…”

21 New compounds and structures in the solid state

“…A careful study by X-ray diffraction and electron microscopy elucidated the structures of the A(VO) 3 (P 2 O 7 ) 2 vanadium(IV) pyrophosphates (A Sr, Pb, Ba). 67 These phases exhibit two closely-related polymorphic forms (a and b) which may exist as intergrowths in one crystallite. Effenberger 68 The crystal structure 69 of Pb 4 BiO 4 PO 4 demonstrates the stereochemical activity of both the nominal Bi 3 and Pb 2 6s 2 lone pairs.…”