Crystal structures of new indium phosphate materials

Abstract

The title compound is tetragonal, P-421c, a = 13.275(3) Å, c = 5.500(2) Å, Z = 4. The structure refinement converged to R1 = 0.0442. On the basis of the Xray diffraction refinement the formula is Bi2PbMnP2O12. The crystal is an inverse twin. Electron diffraction revealed that the X-ray diffraction lattice parameters are from a subcell. The true unit cell is 2a, 2b, 3c. Single-crystal electron diffraction data lead to an apparent wave vector q = 1/2a + 1/2b + 1/3c, compatible with the Bravais lattice 4/mmmP(½ ½ γ ). However, this choice leads to forbidden reflections due to the presence of a 21 axis. An assumption that the crystal consists of a modulated, twinned orthorhombic structure with space group Ccc2 based on the cell (2a) 2 , (2b) 2 , c leads to a modulation vector q = a + γ (c). The (3+1) dimensional Bravais lattice becomes mmmC(10γ) and the super space group is Ccc2(10γ). The refinement of the single crystal x-diffraction data based on Ccc2 consisting of two 90° twin domains led, as expected, to the identical result as the refinement in P-421c. The crystal structure was determined from the X-ray diffraction intensities based on the subcell and represents an averaged structure. The PO4 radical can be present in two orientations. Pb occupies only ½ of the crystallographic 8e positions. The Pb atoms bond through oxygen atoms from PO4 to form a ring, creating channels parallel to c. Manganese and oxygen are present within the channels but the average structure prevents the determination of their location with certainty. Four samples Se, SSe40, SSe30 and SSe20 were prepared as bulk in the amorphous phase and then to the polycrystalline phase by annealing at 373 K for 5, 20, and 120 minutes. The trend of the amorphous and polycrystalline diffraction patterns was similar, which indicates that the basic structural units in both states are also similar. The results showed that the changes in the structural parameters for samples SSe40 and SSe30 are different from that of sample SSe20 these discrepancies are being discussed in terms of: the peak shifts in both the amorphous and crystalline state, the percentage of sulfur compositional variations, stress and crystallite size and finally in terms of the probable site occupancy of the sulfur atoms in the selenium structure. 1) From the results, we noticed that for the four samples the crystallite size is increased by the annealing time and the microstrain is decreased. 2) The crystallite size for SSe40 and SSe30 is always less than that of pure selenium. 3) In case of SSe20 the situation is different. 4) The discrepancies in these findings were due to the site occupancy of sulfur atom in the structural units of selenium. A novel layered tin(IV) phosphate, Sn(HPO4)·(NH3).(H2O)0.6, is synthesized under mild hydrothermal conditions. The crystal structure is solved for powder X-ray diffraction data. The unit cell is trigonal, a = 4.9751(2) Å, c = 22.5983(8) Å, space group R-3, Z = 3. The interlayer water and ammonia molecules are located in a disordered way in the same...