ChemInform Abstract: Topotactic Solid‐State Metal Hydride Reductions of Sr₂MnO₄.

Abstract

Topotactic Solid-State Metal Hydride Reductions of Sr 2MnO4. -The reactivity and mechanism of the solid state topotactic reduction of Sr 2MnO4 using the series of metal hydrides LiH, NaH, CaH 2, MgH2, SrH2, and BaH2 are characterized by powder XRD and TGA/DTA. In terms of reactivity the metal hydrides show the trend MgH2 < SrH2 < LiH  CaH2  BaH2 < NaH. NaH and SrH2 allow for targeted synthesis of reduced Sr 2MnO4-x (0  x  0.37) phases. Sr2MnO3.63 crystallizes in the monoclinic space group P2 1/c with Z = 8, and exhibits an oxidative monoclinic to tetragonal transition at 450 C. Sr2MnO3.69 crystallizes in the tetragonal space group I4/mmm with Z = 2. -(HERNDEN, B. C.; LUSSIER, J. A.; BIERINGER*, M.; Inorg. Chem. 54 (2015) 9, 4249-4256, http://dx.

Topotactic Reduction toward a Noncentrosymmetric Deficient Perovskite Tb0.50Ca0.50Mn0.96O2.37 with Ordered Mn Vacancies and Piezoelectric Behavior

“…These Mn(1)O 5 pyramids are different from those self-connected pyramids in Ca 2 MnO 3.5 54 and Sr 2 MnO 4 . 55 The BVS calculation clearly demonstrates charge ordering for Mn(3), Mn(2), Mn(4), and Mn(5) in expended lattice, that is, ∼2+ for tetragonal Mn(3), edge-shared octagonal Mn(2), and bipyramidal Mn(4); and ∼3+ for octagonal Mn(5). However, the Mn(1) exhibits an averaged valence of ∼2.5+, and we fail to figure out its valence distribution.…”

Kinetics of the Topochemical Transformation of (PbSe)m(TiSe2)n(SnSe2)m(TiSe2)n to (Pb0.5Sn0.5Se)m(TiSe2)n

“…Understanding the kinetics of solid-state reactions is particularly important in the formation of metastable phases, but it is challenging to obtain detailed information about most solid-state reactions because reactants are typically powders and the reactions and structural changes occur at the many surfaces and interfaces. Solid-state reactions are typically monitored by tracking changes in unit cell volume, 1 by tracking the ratio of reactants and products and their structural evolution using Rietveld refinement of diffraction data, 2−4 or via in situ electron microscopy and electron diffraction studies. 5 In situ X-ray diffraction techniques have been used to probe solid-state reactions 6,7 and more complex synthesis methods such as solvothermal approaches.…”

“…These reactions are of vital importance for battery applications, where the commercial technology depends on the reversibility of the topotactic reactions. 12,13 Other topotactic reactions of interest include intercalation of large organic molecules into layered clay structures for sensing applications, 14 transition metal oxide reductions, 1 and the redox synthesis of metastable magnetic phases. 4 Layered compounds, because of the obvious diffusion pathways parallel to the layers and preferred orientation that enhances reflection intensities in diffraction experiments, are particularly attractive for in situ studies of topotactic reactions.…”