Bi3+/M2+ Oxyphosphate: A Continuous Series of Polycationic Species from the 1D Single Chain to the 2D Planes. Part 2: Crystal Structure of Three Original Structural Types Showing a Combination of New Ribbonlike Polycations

Modification strategies for enhancing the visible light responsive photocatalytic activity of the BiPO4nano-based composite photocatalysts

The present issues related to environmental purification have led to a great need for the development of a superior oxidation process to solve the life-threatening problem. The use of the BiPO₄nanomaterial in photocatalysis is one of the best methods for the treatment of wastewater due to its less harmful nature.

Bi3(PO4)O3, the Simplest Bismuth(III) Oxophosphate: Synthesis, IR Spectroscopy, Crystal Structure, and Structural Complexity

The bismuth(III) oxophosphate Bi₃(PO₄)O₃ was obtained by hydrothermal synthesis. The unit cell has a = 5.6840(6) Å, b = 7.0334(7) Å, c = 9.1578(9) Å, α = 78.958(2)°, β = 77.858(2)°, γ = 68.992(2)°, V = 331.41(6) ų, space group P1̅, and Z = 2. The crystal chemical formula that reflects the presence of oxo-centered tetrahedra and triangles is ^2D[O^IIIO^IV₂Bi₃](PO₄). The crystal structure contains [O₃Bi₃]³⁺_∞∞-heteropolyhedral corrugated layers parallel to (001), which alternate along [001] with isolated (PO₄) tetrahedra. The structural complexity parameters are v = 22 atoms, I_G = 3.459 bits/atoms, and I_G,total = 76.107 bits/unit cell, and thus Bi₃(PO₄)O₃ is the simplest pure bismuth(III) oxophosphate.

Long-range antiferromagnetic order and possible field induced spin-flop transition in BiMnVO5

We report the bulk magnetic characterization of a dimeric chain material, BiMnVO₅, by means of magnetic susceptibility, magnetization and heat capacity measurements. Our results provide compelling evidence of an antiferromagnetic (AFM) transition at (T _N) ~ 11.5 K. Moreover, the magnetic entropy change in zero field saturates to 14.6 J mol^-1 K^-1 which is close to the total spin entropy of Mn²⁺. The development of long-range magnetic order in this chain material demonstrates the interplay of strong intra-chain and inter-chain interactions between the dimers, in addition to the intra-dimer interaction. Low-temperature (T  <  T _N) heat capacity data indicate the presence of a gap (Δ/k _B  ≈  5 K) in the spin excitations. Furthermore, the isothermal magnetization below T _N shows an anomaly in the slope between 30 and 40 kOe which is suggestive of a spin-flop transition. Such a low-field spin-flop transition and gapped spin wave excitations may be attributed to the presence of (weak) magnetic anisotropy in this material. We attempt to construct a phase diagram in the magnetic field-temperature plane by extracting data from in-field heat capacity and isothermal magnetization measurements.

Minerals with antiperovskite structure: a review

Antiperovskites or inverse perovskites are inorganic compounds with a perovskite structure but with cations replaced by anions and vice versa. It is shown that there exists a number of minerals whose structures can be regarded as based upon antiperovskite units composed of face-and corner-sharing octahedra. The structures of sulphohalite, galeite, schairerite, kogarkoite, nacaphite, arctite, polyphite, hatrurite and related compounds are considered. The 3C, 2H, 5H, 7H, 9Rand 15Rantiperovskite polytypes are described. In some cases, antiperovskite modules are intercalated with intermediate ions and complexes.

Lead Rare-Earth Oxyhalides: Syntheses and Characterization of Pb6LaO7X (X = Cl, Br)

Yellowish elongated crystals of the two new compounds Pb6LaO7Br (1) and Pb6LaO7Cl (2) have been obtained by the method of solid-state reactions. Both structures can be described in the terms of oxo-centered tetrahedra. The structures of 1 and 2 consist of [O7Pb6La]+ chains that are built from oxocentered OA4 (A = Pb, La) tetrahedra. The halogen ions connect the chains through weak Pb-X bonds. An arrangement of eight OA4 tetrahedra that all share the same central La atom forms a [O8Pb10La3]13+ cluster. The clusters are linked into chains, and additional OPb4 tetrahedra are attached to the chains. Incorporation of Cl atoms instead of Br atoms into the structure causes a lowering of the symmetry from Cmcm to C2/m.

Bi3+/M2+ Oxyphosphate: A Continuous Series of Polycationic Species from the 1D Single Chain to the 2D Planes. Part 1: From HREM Images to Crystal-Structure Deduction

This work deals with the crystal-structure deduction of new structural types of Bi3+-M2+ oxyphosphates (M is a transition element) from HREM images. Previous studies showed the unequivocal attribution of particular HREM contrasts to the corresponding Bi/M/O-based polycationic species in similar materials. On this basis, the examination of isolated crystallites of polyphased samples led to new HREM contrasts assigned to new polycationic species in three new structural types. This helped us to solve one crystal structure, and the two other forms have been deduced through HREM image decoding. It helped to model the investigated materials from the structural point of view as well as the chemical one. The three assumed crystal structures are formed by polycationic ribbons, n tetrahedra wide, surrounded by PO4 groups, as already encountered in these series of oxyphosphates. However, here we deal with the original n= 4-6 cases, whereas, up to this work, only the n= 1-3 ribbons have been reported. The greater size of ribbons is associated with particular structural modifications responsible for complex HREM contrasts. The validity of the proposed models is verified in Part 2 of this work.