Pressure Induced Octahedral Tilting Distortion in Ba2YTaO6

Herein we communicate the first example of a pressure induced octahedral tilting distortion in a double perovskite phase, which was observed during the structural characterization of Ba2YTaO6 using high-pressure synchrotron X-ray powder diffraction

Structural Studies of Sr\u3csub\u3e2\u3c/sub\u3eGaSbO\u3csub\u3e6\u3c/sub\u3e, Sr\u3csub\u3e2\u3c/sub\u3eNiMoO\u3csub\u3e6\u3c/sub\u3e, and Sr\u3csub\u3e2\u3c/sub\u3eFeNbO\u3csub\u3e6\u3c/sub\u3e Using Pressure and Temperature

Results from high-pressure synchrotron x-ray diffraction and high-temperature x-ray diffraction measurements on polycrystalline samples of the tetragonal perovskites Sr2GaSbO6, Sr2NiMoO6, and Sr2FeNbO6 are reported. A phase transition, where the unit cell changes symmetry from tetragonal to cubic, is observed for each compound at elevated temperatures. The phase transition changes the structure from one exhibiting an octahedral tilting distortion at ambient temperature to one that is untilted above the transition temperature. At elevated pressures the lattice parameter ratio increases, indicating that the magnitude of the octahedral tilting distortion is increasing as a function of pressure. In the pressure range studied, up to ~6 GPa, no phase transitions were observed

Pressure-Induced Phase Transition and Octahedral Tilt System Change of Ba\u3csub\u3e2\u3c/sub\u3eBiSbO\u3csub\u3e6\u3c/sub\u3e

High-resolution X-ray synchrotron powder diffraction studies under high-pressure conditions are reported for the ordered double perovskite Ba2BiSbO6. Near 4 GPa, the oxide undergoes a pressure-induced phase transition. The symmetry of the material changes during the phase transition from space group R3¯ to space group I2/m, which is consistent with a change in the octahedral tilting distortion from an a−a−a− type to a0b−b− type using the Glazer notation. A fit of the volume–pressure data using the Birch–Murnagaham equation of stateyielded a bulk modulus of 144(8) GPa for the rhombohedral phase

Single-Crystal Structure of the 2H-Related Perovskites (A\u3csub\u3e3-x\u3c/sub\u3eNa\u3csub\u3ex\u3c/sub\u3e)NaBO\u3csub\u3e6\u3c/sub\u3e (A = La, Pr, Nd; B = Rh, Pt)

Single crystals of La2.47Na1.53RhO6, Pr2.45Na1.55RhO6, Nd2.45Na1.55RhO6, La2Na2PtO6, and Nd2Na2PtO6 were grown from carbonate and “wet” hydroxide fluxes. All were found to crystallize in the trigonal space group R3̄c and adopt the K4CdCl6 structure

Connecting Small Ligands to Generate Large Tubular Metal-Organic Architectures

The new metal-organic framework materials, ZnF(Am2TAZ)·solvents and ZnF(TAZ)·solvents (Am2TAZ=3,5-diamino-1,2,4-triazole, TAZ=1,2,4-triazole), have been synthesized solvothermally and structurally characterized by either Rietveld refinement from powder XRD data or by single crystal X-ray diffraction. The three-dimensional structures of the compounds display open-ended, tubular channels, which are constituted of covalently bonded hexanuclear metallamacrocycles (Zn6F6(ligand)6). The tubular channels are subsequently covalently joined into a honeycomb-like hexagonal array to generate the three-dimensional porous framework. In the case of ZnF(Am2TAZ)·solvents, hydrophilic –NH2 groups point into the channels, effectively reducing their inner diameter relative to ZnF(TAZ)·solvents. The present compounds are isostructural to one another and to the previously reported ZnF(AmTAZ)·solvents (AmTAZ=3-amino-1,2,4-triazole), illustrative of the fact that the internal size and chemical properties of the framework may be altered by modification of the small, heterocyclic ligand. In addition to demonstrating the ability to modify the basic framework, ZnF(TAZ)·solvents and ZnF(Am2TAZ)·solvents are two of the most thermally stable coordination frameworks known to date