인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

Colossal magnetoresistance (CMR) phenomena are observed in the perovskite-type hole-doped manganites in which the double-exchange ferromagnetic metal phase and the charge–orbital ordered antiferromagnetic phase compete with each other. The quenched disorder arising from the inherent chemical randomness or the intentional impurity doping may cause major modifications in the electronic phase diagram as well as in the magnetoelectronic properties near the bicritical point that is formed by such a competition of the two phases. One is the phase separation phenomenon on various time-scales (from static to dynamic) and on various length-scales (from glass-like nano to grain-like micron). The other is the enhanced phase fluctuation with anomalous reduction in the transition temperatures of the competing phases (and hence in the bicritical-point temperature). The highly effective suppression of such a phase fluctuation by an external magnetic field is assigned here to the most essential ingredient of the CMR physics. Such profound and dramatic features as appearing in the bicritical region are extensively discussed in this paper with ample examples of the material systems specially designed for this purpose. The unconventional phase-controls over the competing phases in terms of magnetic/electric fields and photo-excitations are also exemplified.

https://iopscience.iop.org/article/10.1088/0034-4885/69/3/R06/pdf

Critical features of colossal magnetoresistive manganites

Manganese-activated fluoride phosphors for high-efficacy warm white light-emitting diodes have been limited by low photoluminescence quantum yields. Here, Zhu et al. use an efficient cation exchange reaction to synthesize manganese phosphors with photoluminescence quantum yields as high as 98%.

/pdf/highly-efficient-non-rare-earth-red-emitting-phosphor-for-3wgxp231in.pdf

Highly efficient non-rare-earth red emitting phosphor for warm white light-emitting diodes

The manipulation of magnetic properties by an electric field in magnetoelectric multiferroic materials has driven significant research activity, with the goal of realizing their transformative technological potential. Here, we review progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and the exploration of devices and applications. Focusing on the translation of the many scientific breakthroughs into technological innovations, we identify the key open questions in the field where targeted research activities could have maximum impact in transitioning scientific discoveries into real applications. Magnetoelectric multiferroics, where magnetic properties are manipulated by electric field and vice versa, could lead to improved electronic devices. Here, advances in materials, characterisation and modelling, and usage in applications are reviewed.

Advances in magnetoelectric multiferroics.

Abstract Cation ordering in ABX3 perovskites is important to structural, physical and chemical properties. Here we report discovery of CaCuFeReO6 with the tetragonal AA′BB′O6 double double perovskite structure that was previously only reported for A′=Mn compositions. CaCuFeReO6 occurs in the same phase field as CaCu3Fe2Re2O12 demonstrating that different A‐cation ordered peroskites may be obtained in the same chemical system. CaCuFeReO6 has ferrimagnetic order of Fe, Re and Cu spins below T C=567 K, in contrast to Mn analogues where the Mn spins order separately at much lower temperatures. The magnetoresistance of CaCuFeReO6 displays low‐field “butterfly” hysteresis with an unusual change from negative to positive values as field increases. Many more AA′BB′O6 double double perovskites may be accessible for A′=Cu and other divalent transition metals at high pressure, so the presently known phases likely represent only the “tip of the iceberg” for this family.

/pdf/1-1-ca2-cu2-a-site-order-in-a-ferrimagnetic-double-double-1cv3n6a7.pdf

1 : 1 Ca2+:Cu2+ A‐site Order in a Ferrimagnetic Double Double Perovskite

The design and development of non-precious metal catalysts with high activity and stability for overall water splitting remains a major challenge. Herein, lamellar FeNi3N incorporated by FeNi3 is synthesized via thermal ammonolysis. The abundance of hollow sites in this FeNi3–FeNi3N heterostructure significantly enhances the intrinsic activity towards hydrogen evolution reaction, while the heterostructure also offers high electrochemical active surface area for oxygen evolution reaction. FeNi3–FeNi3N enables a lower overpotential for both hydrogen and oxygen evolution electrocatalysis in alkaline media. When FeNi3–FeNi3N is employed as a bifunctional material for overall water splitting, it shows a cell voltage of only 1.5 V at 10 mA cm−2 and offers stable performance for up to 48 h at current densities of ∼40 mA cm−2.

FeNi3–FeNi3N – a high-performance catalyst for overall water splitting

The switch in local Jahn–Teller distortions of the MnIIIO6 octahedra caused by the topotactic ion-exchange reaction of MnAsO4·H2O to give LiMnAsO4(OH) results in a novel switch from antiferromagnetic to ferromagnetic order within infinite Mn–O–Mn chains in the framework, although in both materials the overall order is antiferromagnetic.

Chemical switching of magnetic properties through topotactic lithium exchange in manganese(III) arsenate hydrate

Phosphates contain oxyanions of phosphorus(V). The most common anion is the orthophosphate group PO4 3 −, which is found in many solid phosphates, including hydrated and acid phosphate salts. Oligomeric polyphosphate chains P n O3 n +1 ( n +2)− up to n = 6 and cyclophosphate rings P n O3 n n − up to n = 12 are also observed, and a unique cage ultraphosphate anion P8O23 6− is found in the Na3FeP8O23 structure. Polymeric phosphate anions include the infinite chain catenaphosphate anion (PO3 −)∞ and the ultraphosphate networks found in CaP4O11 and the lanthanide MP5O14 structures. Many compound anions and neutral frameworks such as silicophosphates, aluminophosphates, and molybdenum phosphates also exist. Phosphate species are characterized through P–O stretching and bending vibrations in infrared and Raman spectroscopies, and by 31P NMR. Phosphate structures are generally rigid, resistant to chemical attack, and (when anhydrous) insoluble and thermally stable. Some phosphate crystals have important physical properties such as ferroelectricity in KH2PO4 (potassium dihydrogenphosphate, KDP). Diffusion of extra-framework ions leads to potential uses of solid phosphates as ion exchangers and conductors, for example, NASICON based on NaZr2(PO4)3, and LiFePO4 as a cathode material for lithium-ion batteries. Vanadium phosphates are important selective oxidation catalysts. Large pore phosphates in which molecules can be adsorbed and undergo acid-catalyzed reactions have been intensively studied. These materials are crystalline microporous solids such as aluminophosphates, or lamellar structures, typically based on α-Zr(HPO4)2·H2O that can be pillared. This area of interest has led to the synthesis of many new organically templated metal phosphates, usually through hydrothermal reactions. Hydrated and acid orthophosphates can also be prepared in solution, and anhydrous phosphates are synthesized by direct high-temperature reactions and from phosphate-rich melts or fluxes. Slow cooling of melts is used to grow crystals, and quenching can result in many stable phosphate glasses. Phosphate anions do not absorb significantly in the UV–visible region and so solid phosphates also find use as optical materials such as phosphors, nonlinear crystals (e.g., KTiOPO4), and lasers. Solid phosphates constitute many minerals, notably apatites, which are also found in living organisms as rigid components such as bones and teeth. Synthetic calcium phosphate biomaterials are used for bone implants.


Keywords:

orthophosphate;
phosphate;
ionically conducting phosphates;
microporous phosphate materials;
mineral phosphates;
nonlinear optical phosphate materials;
condensed phosphate polyanions;
layered phosphate materials;
biomaterial phosphates

Phosphates: Solid-State Chemistry

A series of Sr2Fe1−xMgxMoO6 ( 0 ⩽ x ⩽ 1 ) double perovskite oxides have been prepared and their crystal, magnetic and transport properties studied. Rietveld refinements, in tetragonal space group I4/m, show an almost complete B-cation ordering in the doped samples. A systematic decrease in Curie temperature, TC and saturation magnetization, MS with increase of x has been observed in this solid solution series. Resistivities show a semiconducting behavior for all samples and increase with x. The x = 0 sample becomes metallic above a metal-insulator transition temperature of 45 K in applied fields of 30 and 50 kOe. Negative colossal magnetoresistances (CMR) have been observed (up to 47% for the x = 0.6 sample at 5 K) in all the samples and these MR effects show a strong dependence on the microstructural nature (grain boundaries) of the material.

J. Paul Attfield

Papers

1 : 1 Ca2+:Cu2+ A‐site Order in a Ferrimagnetic Double Double Perovskite

FeNi3–FeNi3N – a high-performance catalyst for overall water splitting

Chemical switching of magnetic properties through topotactic lithium exchange in manganese(III) arsenate hydrate

Phosphates: Solid-State Chemistry

Structural, Magnetic and Transport Properties of Sr2Fe1‐xMgxMoO6 (0 ≤ x ≤ 1) Double Perovskites.