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A series of d10 coinage metal thiosalicylate coordination polymers (CPs) is reported. The 1D structures of the three CPs are formed by M3S3 fused hexagons for Cu and Ag compounds and interpenetrated helical chains for Au CP. Depending on the metal, solid‐state red and NIR emissive CPs are obtained with quantum yields up to 50 %, providing a great opportunity to replace the actual emissive critical raw materials. [ABSTRACT FROM AUTHOR]

The effects of Zn vacancies on the physical properties of antiperovskite compounds Mn3Zn x N (x =0.96 and 0.93) were investigated. For Mn3Zn0.96N, lowering the temperature produced two anomalies in the magnetization and heat capacity curves: the first at ∼185K is related to magnetic ordering and was accompanied by a lattice expansion; the second at ∼115K is due to a magnetic order change and showed a lattice contraction. However, for Mn3Zn0.93N only a single transition is observed around 185K. [ABSTRACT FROM AUTHOR]

The effect of the substitution of yttrium for bismuth in BiCrO3 distorted perovskite has been investigated by means of magnetic measurements and symmetry mode analysis of neutron and x-ray powder diffraction data. Bi1-xYxCrO3 compounds were synthesized under high pressure and high temperature. Magnetic and structural phase diagrams were established by means of magnetization measurements and x-ray and neutron powder diffraction. We found that the monoclinic distorted structure is replaced by an orthoferrite-type orthorhombic structure at x ⩾0.05. Symmetry adapted analysis was performed, indicating the importance of the LD3 distortion mode for the stabilization of the monoclinic structure and its antiferroelectric arrangement. The interplay between crystal distortion modes and magnetic properties is discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Single phase PbVO3 samples were prepared by using a two stage synthesis method. [•] The shape of the Bragg peaks was analyzed with an anisotropic peak broadening model. [•] The magnetic susceptility of PbVO3 was fitted using the FSL model. [•] EPR spectra revealed the presence of a hyperfine structure due to the V4+ cations. [•] Raman spectra confirmed the P4mm space group of PbVO3. [Copyright &y& Elsevier]

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa. We show that BiMnO3 displays under pressure a rich sequence of five phases with a great variety of structures and properties, including a metallic phase above 53 GPa and, between 37 and 53 GPa, a strongly elongated monoclinic phase that allows ferroelectricity, which contradicts the traditional expectation that ferroelectricity vanishes under pressure. Between 7 and 37 GPa, the Pnma structure remains remarkably stable but shows a reduction of the Jahn-Teller distortion in a way that differs from the behavior observed in the archetypal orthorhombic Jahn-Teller distorted perovskite LaMnO3. [ABSTRACT FROM AUTHOR]

Abstract: α-[C6H4(NH3)2]2Bi2I10, which is a new material containing low-dimensional iodobismuthate anions, was synthesized and through its single crystal X-ray diffraction measurements, was proven to crystallize at room temperature in the centrosymmetric space group P21 /c. It consists of a p-phenylenediammonium dication and a discrete (0-D) anion built up of edge-sharing bioctahedron. Due to the hydrogen bonds and the interatomic distances (Bi–I, I⋯I and π–π) changes, α-phase was transformed into the corresponding centrosymmetric β-phase, β-[C6H4(NH3)2]2Bi2I10, through a single-crystal to single-crystal transformation occurring upon cooling to −28/−26°C. Below the transition temperature, β-[C6H4(NH3)2]2Bi2I10 crystallizes in the monoclinic system, centrosymmetric space group P21 /n. Besides, the optical transmission measurements on α-[C6H4(NH3)2]2Bi2I10 thin films have revealed two absorption bands at 2.47 and 3.01eV. Finally, two room temperature photoluminescence emissions attributed to excitons radiative recombinations confined within the bioctahedra Bi2I10 4−, were observed in the red spectral range at 1.9 and 2.05eV energy. [Copyright &y& Elsevier]

We report the preparation and structural analysis of the LaCuO2.66 compound. The synthesis is carried out by low temperature (280 °C) oxidation of the LaCuO2 delafossite. The structure is solved and refined by combined use of electron microscopy, X-ray and neutron powder diffraction. On introduction of oxygen in the copper planes, the 3R rhombohedral stacking of the parent delafossite is reorganized to yield an hexagonal type of stacking. The original copper planes forming a simple triangular lattice are rearranged into a kagome lattice of corner sharing copper cation triangles centered by oxygen anions. This is accompanied by a shortening by ≈√ of 3/2 of the Cu&z.sbnd;Cu distances from ≈3.85 A˚ to ≈3.35 A˚. These major structural modifications bring about the existence of stacking faults, visible on electron, X-ray and neutron diffraction data, and difficult to take into account in the refinements. Pair distribution function analysis of synchrotron powder diffraction data is used to obtain a direct confirmation of the structure. [Copyright &y& Elsevier]

Polycrystalline samples of 6H-B Ba3NiSb2O9 are obtained from the ambient pressure 6H-A modification by hot-press sintering (anvil cell, 2-4 GPa, 400-680 °C). [ABSTRACT FROM AUTHOR]

The discovery of a universal memory that exhibits fast access speed, high-density storage, and non-volatility has fuelled research into phase-change materials over the past decades. In spite of the efficiency of the inorganic chalcogenides for phase-change random access memory (PCRAM), they still have some inherent drawbacks, such as high temperature required for phase change and difficulty to control the domain size of the phase change, because of their brittleness. Here we present a Au I -thiolate coordination polymer which undergoes two successive phase changes on application of mild heating (<200 °C) from amorphous-to-crystalline1-to-crystalline2 phases. These transitions are reversible upon soft hand grinding. More importantly, each phase exhibits different photoluminescent properties for an efficient optical read-out. We believe that the ability of the Au I -thiolate coordination polymer to have reversible phase changes under soft conditions and at the same time to display distinct optical signals, can pave the way for the next generation of PCRAM., (© 2022 Wiley-VCH GmbH.)

In the framework of expanding the range of copper-based compounds in the pyroxene family, we have synthesized at high pressure and high temperature a powder containing a mixture of a new phase with stoichiometry Sr 5 CuGe 9 O 24 having two identified impurity phases. Electron crystallography showed that the new phase crystallizes in the monoclinic space group P2/c, with unit-cell parameters a = 11.8 Å, b = 8.1 Å, c = 10.3 Å and β = 101.3°. We applied the recently developed low-dose electron diffraction tomography method to solve the structure by direct methods. The obtained structure model contains all 9 independent cation positions and all 13 oxygen positions. A subsequent refinement against powder X-ray diffraction data ascertained the high quality of the structure solution, in particular, the unusual structural arrangement that there are three different environments for Ge in this phase.

In the search for frustrated spin interactions, a YCuO 2.66 phase has been synthesized by a treatment under oxygen pressure of YCuO 2.5 . X-ray powder diffraction and electron diffraction studies have been conducted. Electron diffraction shows that the sample is twinned on a 10 nm scale. Precession electron diffraction data obtained from a twinned crystal was treated in order to obtain intensities corresponding to only one of the orientations of the twins. From this data a structure solution was obtained where, as in YCuO 2.5 , the Cu atoms form triangular planes. The Cu atoms are linked in two dimensions by oxygen atoms in the present structure whereas in YCuO 2.5 they are only linked in one-dimensional chains.

The oxygen reduction reaction (ORR) activity of Pt-alloy electrocatalysts depends on (i) the strain/ligand effects induced by the non-noble metal (3d-transition metal or a rare-earth element) alloyed to Pt, (ii) the orientation of the catalytic surfaces, and (iii) the density of structural defects (SDs) (e.g., vacancies, voids, interconnections). These SDs influence the "generalized" coordination number of Pt atoms, the Pt-alloy lattice parameter, and thus the adsorption strength of the ORR intermediates (O*, OH*, OOH*). Here, we discuss a set of parameters derived from CO ads stripping measurements and the Rietveld refinement of X-ray diffraction (XRD) patterns, aiming to show how the leaching of the non-noble metal and the density of SDs influence the ORR activity of porous hollow PtNi/C nanoparticles (PH-PtNi/C NPs). PH-PtNi/C NPs were aged at T = 353 K in an Ar-saturated 0.1 M HClO 4 electrolyte during 20 000 potential cycles between E = 0.6 and 1.0 V versus the reversible hydrogen electrode, with an intermediate characterization after 5000 cycles. The losses in the ORR specific activity were attributed to the dissolution of Ni atoms (modifying strain/ligand effects) and to the increase of the crystallite size (d XRD ), resulting in a diminution of the density of grain boundaries. In agreement with the Gibbs-Thompson equation, the electrocatalysts that presented larger crystallites (d XRD > 3 nm) were far more stable than the ones with the smallest crystallites (d XRD < 2 nm). We also observed that performing intermediate characterizations (in an O 2 -saturated electrolyte) results in activity losses for the ORR.

The compounds of the doubly ordered perovskite family NaLnCoWO 6 (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) were synthesized by solid-state reaction, nine of which (Ln = Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) are new phases prepared under high-temperature and high-pressure conditions. Their structural properties were investigated at room temperature by synchrotron X-ray powder diffraction and neutron powder diffraction. All of them crystallize in monoclinic structures, especially the nine new compounds have the polar space group P2 1 symmetry, as confirmed by second harmonic generation measurements. The P2 1 polar structures were decomposed and refined in terms of symmetry modes, demonstrating that the polar mode is induced by two nonpolar modes in a manner of Hybrid Improper Ferroelectricity. The amplitudes of these three major modes all increase with decreasing the Ln cation size. The spontaneous ferroelectric polarization is estimated from the neutron diffraction data of three samples (Ln = Y, Tb, and Ho) and can be as large as ∼20 μC/cm 2 .

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa. We show that BiMnO3 displays under pressure a rich sequence of five phases with a great variety of structures and properties, including a metallic phase above 53 GPa and, between 37 and 53 GPa, a strongly elongated monoclinic phase that allows ferroelectricity, which contradicts the traditional expectation that ferroelectricity vanishes under pressure. Between 7 and 37 GPa, the Pnma structure remains remarkably stable but shows a reduction of the Jahn-Teller distortion in a way that differs from the behavior observed in the archetypal orthorhombic Jahn-Teller distorted perovskite LaMnO3.

Layered oxides are the subject of intense studies either for their properties as electrode materials for high-energy batteries or for their original physical properties due to the strong electronic correlations resulting from their unique structure. Here we present the detailed phase diagram of the layered P2-Na(x)VO(2) system determined from electrochemical intercalation/deintercalation in sodium batteries and in situ X-ray diffraction experiments. It shows that four main single-phase domains exist within the 0.5≤x≤0.9 range. During the sodium deintercalation (intercalation), they differ from one another in the sodium/vacancy ordering between the VO(2) slabs, which leads to commensurable or incommensurable superstructures. The electrochemical curve reveals that three peculiar compositions exhibit special structures for x  =  1/2, 5/8 and 2/3. The detailed structural characterization of the P2-Na(1/2)VO(2) phase shows that the Na(+) ions are perfectly ordered to minimize Na(+)/Na(+) electrostatic repulsions. Within the VO(2) layers, the vanadium ions form pseudo-trimers with very short V-V distances (two at 2.581 Å and one at 2.687 Å). This original distribution leads to a peculiar magnetic behaviour with a low magnetic susceptibility and an unexpected low Curie constant. This phase also presents a first-order structural transition above room temperature accompanied by magnetic and electronic transitions. This work opens up a new research domain in the field of strongly electron-correlated materials. From the electrochemical point of view this system may be at the origin of an entire material family optimized by cationic substitutions.