Mn- and Yb-Doped BaTiO-(NaBi)TiO Ferroelectric Relaxor with Low Dielectric Loss.

In this work, a Mn-and Yb-doped BaTiO-(NaBi)TiO ferroelectric relaxor was designed and prepared. The effects of Mn on the microstructures, dielectric and electrical properties of the ceramics were investigated. The X-ray structural analysis shows a perovskite structure.

AgMoO: an oxide solid-state Ag electrolyte.

AgMoO powders and micro-crystals were prepared at 400 °C for 24 h and 500 °C for 6 h using solid-state reactions. The AgMoO samples crystalized in a triclinic 1̄ space group with the cell parameters = 6.0972(1) Å, = 7.

Structure Evolution of NaO from Room Temperature to 500 °C.

NaO is one of the possible discharge products from sodium-air batteries. Here, we report the evolution of the structure of NaO from room temperature to 500 °C using variable-temperature neutron and synchrotron X-ray powder diffraction. A phase transition from α-NaO to β-NaO is observed in the neutron diffraction measurements above 400 °C, and the crystal structure of β-NaO is determined from neutron diffraction data at 500 °C.

Structural and Magnetic Studies of O-Type Ruthenium and Osmium Oxides.

Oxides of the form O with = K, Rb, Cs and = Ru and Os have been synthesized and characterized by diffraction and magnetic techniques. For = K the oxides adopted the tetragonal (4/) scheelite structure. RbOsO, which crystallizes as a scheelite at room temperature, underwent a continuous phase transition to 4/ near 550 K.

Visible photocatalysis of novel oxime phosphonates: synthesis of β-aminophosphonates.

A novel type of oxime phosphonate was synthesized and used in the intermolecular cascade radical addition reaction of alkenes to access β-aminophosphonates via visible-light-driven N-centered iminyl radical-mediated and redox-neutral selective C-P single-bond cleavage in an active phosphorus radical route. The procedure is characterized by its ability to achieve the construction of Csp3-P and Csp3-N bonds without the requirement for oxidants and bases.

Controlling Oxygen Defect Formation and Its Effect on Reversible Symmetry Lowering and Disorder-to-Order Phase Transformations in Nonstoichiometric Ternary Uranium Oxides.

In situ synchrotron powder X-ray diffraction measurements have demonstrated that the isostructural AUO ( A = alkaline earth metal cation) oxides CaUO and α-SrCaUO undergo a reversible phase transformation under reducing conditions at high temperatures associated with the ordering of in-plane oxygen vacancies resulting in the lowering of symmetry. When rhombohedral (space group R3̅ m) CaUO and α-SrCaUO are heated to 450 and 400 °C, respectively, in a hydrogen atmosphere, they undergo a first-order phase transformation to a single phase structure which can be refined against a triclinic model in space group P1̅, δ-CaUO and δ-SrCaUO, where the oxygen vacancies are disordered initially. Continued heating results in the appearance of superlattice reflections, indicating the ordering of in-plane oxygen vacancies.

Squeezing electrons out of 6s lone-pairs in perovskite-type oxides.

Having identified a set of conditions that predispose a solid-state ionic compound to a pressure-induced valence transition, we investigated a series of Bi(iii) perovskite oxides. We found such a transition below 10 GPa in every case, including one that we synthesised for the first time (double perovskite-type Ba2BiOsO6).

Rh(III)-Catalyzed Phosphine Oxide Migration Reactions: Selective Synthesis of 3-Phosphinoylindoles.

3-Phosphinoylindoles are important components of biological active natural products and materials in pharmaceuticals. Herein, a new approach for the synthesis of 3-phosphinoylindoles has been established by a Rh(III)-catalyzed cyclization from readily accessible (2-azidostyryl)diphenylphosphine oxides. This intramolecular transformation occurs through a unique phosphine oxide group migration and offers a straightforward route to rebuild sp C-P bond and construct the indole ring in single step.

Unexpected Crystallographic Phase Transformation in Nonstoichiometric SrUO: Reversible Oxygen Defect Ordering and Symmetry Lowering with Increasing Temperature.

In situ synchrotron powder X-ray diffraction measurements have demonstrated that SrUO undergoes a reversible phase transformation under reducing conditions at high temperatures, associated with the ordering of oxygen defects resulting in a lowering of crystallographic symmetry. When substoichiometric rhombohedral α-SrUO, in space group R3̅ m with disordered in-plane oxygen defects, is heated above 200 °C in a hydrogen atmosphere it undergoes a first order phase transformation to a (disordered) triclinic polymorph, δ-SrUO, in space group P1̅. Continued heating to above 450 °C results in the appearance of superlattice reflections, due to oxygen-vacancy ordering forming an ordered structure δ-SrUO.

Pressure-induced anomalies and structural instability in compressed β-SbO.

Here, we report a high-pressure study of orthorhombic structured β-Sb2O3 (valentinite) by the combination of synchrotron in situ X-ray diffraction and first-principles theoretical calculations at pressures up to 40.5 GPa. Our results reveal that the metastable β-Sb2O3 undergoes an isostructural phase transition at high pressure, yielding a distorted β phase at 7-15 GPa through symmetry breaking and structural distortion as inferred from our XRD analyses and DFT theoretical calculations where pressure-induced elasticity softening is observed at pressures of 7-15 GPa.

Autoxidation Photoredox Catalysis for the Synthesis of 2-Phosphinoylindoles.

A new approach to the synthesis of 2-phosphinoylindoles through photoredox catalysis without external oxidants has been developed. Promoted by a ruthenium photoredox catalyst, a broad scope of 2-phosphinoylindoles can be synthesized through phosphinoylation/cyclization of diphenylphosphine oxide at room temperature under irradiation without external oxidants. The estrone skeleton isocyan is also an amenable substrate for this cyclization, yielding a molecule that has potential medicinal applications.

Pressure induced polymerization of acetylide anions in CaC and 10 fold enhancement of electrical conductivity.

Transformation between different types of carbon-carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure.

The impact of anion ordering on octahedra distortion and phase transitions in SrTaON and BaTaON.

In this work we synthesized BaTaON and SrTaON using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaON [P4/mmm (No. 123)] and SrTaON [I4/mcm (No.

YCa3(CrO)3(BO3)4: A Cr(3+) Kagomé Lattice Compound Showing No Magnetic Order down to 2 K.

We report a new gaudefroyite-type compound YCa3(CrO)3(BO3)4, in which Cr(3+) ions (3d(3), S = 3/2) form an undistorted kagomé lattice. Using a flux agent, the synthesis was significantly accelerated with the typical calcining time reduced from more than 2 weeks to 2 d. The structure of YCa3(CrO)3(BO3)4 was determined by combined Rietveld refinements against X-ray and neutron diffraction data.

Infinitely Adaptive Transition-Metal Ordering in Ln2O2MSe2-Type Oxychalcogenides.

A number of Ln2O2MSe2 (Ln = La and Ce; M = Fe, Zn, Mn, and Cd) compounds, built from alternating layers of fluorite-like [Ln2O2](2+) sheets and antifluorite-like [MSe2](2-) sheets, have recently been reported in the literatures. The available MSe4/2 tetrahedral sites are half-occupied, and different compositions display different ordering patterns: [MSe2](2-) layers contain MSe4/2 tetrahedra that are exclusively edge-sharing (stripe-like), exclusively corner-sharing (checkerboard-like), or mixtures of both. This paper reports 60 new compositions in this family.

Synthesis, structural characterization, and physical properties of the new transition metal oxyselenide Ce2O2ZnSe2.

The quaternary transition metal oxyselenide Ce2O2ZnSe2 has been shown to adopt a ZrCuSiAs-related structure with Zn(2+) cations in a new ordered arrangement within [ZnSe2](2-) layers. The color of the compound changes as a function of cell volume, which can vary by ∼0.4% under different synthetic conditions.

Synthesis, characterisation and properties of rare earth oxyselenides A4O4Se3 (A = Eu, Gd, Tb, Dy, Ho, Er, Yb and Y).

Rare earth oxyselenides A4O4Se3 (A = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Y) were synthesised using solid state reactions and three new structure types (β, γ, and δ) were observed. A4O4Se3 materials adopt either the α (A = Nd, Sm), β (A = Eu), γ (A = Gd, Tb) or δ (A = Dy, Ho, Er, Yb, Y) structure depending on the rare earth radius. Each structure type contains alternating [A2O2](2+) and Se(2-)/Se2(2-) layers.

Promising oxonitridosilicate phosphor host Sr3Si2O4N2: synthesis, structure, and luminescence properties activated by Eu2+ and Ce3+/Li+ for pc-LEDs.

A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa ̅3, Z = 24, and cell parameter a = 15.

Synthesis, structure, and characterization of the series BaBi(1-x)Ta(x)O(3) (0

The series BaBi(1-x)Ta(x)O(3) (0 View Article and Find Full Text PDF