Unusual 180 degrees P-O-P Bond Angles in ZrP(2)O(7)

Enhanced Rh-anchoring on the composite metal phosphate Y0.33Zr2(PO4)3 in three-way catalysis

Rh/Y_0.33Zr₂(PO₄)₃ formed a more thermostable bidentate interfacial linkage compared to the monodentate linkage that formed in Rh/ZrP₂O₇.

Low-Temperature Spark Plasma Sintering of ZrW2-xMoxO₈ Exhibiting Controllable Negative Thermal Expansion

Molybdenum-doped zirconium tungstate (ZrW_2−xMo_xO₈) has been widely studied because of its large isotropic coefficient of negative thermal expansion (NTE). However, low density and poor sinterability limit its production and application. In this study, relative density greater than 90% single-phase ZrW_2−xMo_xO₈ (0.0 ≤ x ≤ 1.0) sintered bodies were fabricated by spark plasma sintering (500–600 °C for 10 min) using ZrW_2−xMo_xO₇(OH)₂·2H₂O precursor powders as the starting material. High-temperature X-ray diffraction and thermomechanical analysis were used to investigate the change in the order–disorder phase transition temperature of the sintered materials; it gradually dropped from 170 °C at x = 0.0 to 78 °C at x = 0.5, and then to below room temperature at x ≥ 0.7. In addition, all sintered bodies exhibited NTE behavior. The NTE coefficient was controllable by changing the x value as follows: from −7.85 × 10⁻⁶ °C⁻¹ (x = 0) to −9.01 × 10⁻⁶ °C⁻¹ (x = 0.6) and from −3.22 × 10⁻⁶ °C⁻¹ (x = 0) to −2.50 × 10⁻⁶ °C⁻¹ (x = 1.0) before and after the phase transition, respectively. Rietveld structure refinement results indicate that the change in the NTE coefficient can be straightforwardly traced to the thermodynamic instability of the terminal oxygen atoms, which only have one coordination.

Electrochemical lithiation/delithiation of SnP2O7 observed by in situ XRD and ex situ7Li/31P NMR, and 119Sn Mössbauer spectroscopy

The lithiation of the SnP₂O₇ anode material leads to tin extrusion and formation of Li_xSn alloys with stable capacity during the subsequent cycles.

The 136-atom structure of ZrP2O7 and HfP2O7 from powder diffraction data

There has been considerable debate in the literature about the true room-temperature structure of ZrP2O7 and related materials. In this article we describe how a combination of information from solid-state 31P NMR and powder diffraction data can be used to determine the structure of this 136 unique-atom material. The structure has been solved using a combination of simulated annealing and Rietveld refinement performed simultaneously on X-ray and neutron diffraction data. Despite the close to cubic metric symmetry of the material, we show how its true orthorhombic structure (space group Pbca) can be refined to a high degree of precision.

The room-temperature superstructure of ZrP2O7 is orthorhombic: there are no unusual 180 degrees P-O-P bond angles

The structure of room-temperature ZrP2O7 is shown to be orthorhombic by a combination of high-resolution synchrotron powder diffraction and single-crystal synchrotron diffraction data. Small nontwinned single crystals were obtained by synthesizing the compound using solvothermal methods at temperatures below the cubic to orthorhombic phase transition. The average P-O-P angle is 146 degrees. DFT calculations (B3LYP/AUG-cc-pVDZ) on the isolated P2O7(4-) anion yield a P-O-P angle of 153.42 degrees and indicate that the barrier to inversion is of the order 3.6 kJ mol(-1).