A new layered pnictide oxide (Fe2P2)(Sr4Sc2O6) has been synthesized by solid-state reaction. This material has an alternating layer stacking structure of anti-fluorite Fe2P2 and perovskite-based Sr4Sc2O6 oxide layers. The space group of the material is P4/nmm and the lattice constants a and c are 4.016 and 15.543 A, respectively. The interlayer Fe–Fe distance corresponding to the c-axis length is the longest ever reported in the iron-based pnictides. In both magnetization and resistivity measurements, the present compound exhibited superconductivity below 17 K; this temperature is much higher than that for LaFePO and the highest in arsenic-free iron-based pnictide systems under ambient pressure.

https://iopscience.iop.org/article/10.1088/0953-2048/22/7/075008/pdf

Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer

The details of the ion-exchange properties of the layered sulfide material K2xMnxSn3−xS6 (x = 0.5−0.95) (KMS-1) with Cs+ and Rb+ cations are reported. X-ray photoelectron spectroscopy (XPS), elemental analyses, and powder and single-crystal diffraction studies revealed that the Cs+ and Rb+ ion exchange of KMS-1 is complete (quantitative replacement of K+ ions) and topotactic. These data also revealed that the Cs+ exchange is accompanied with a rare topotactic oxidation of Mn2+ to Mn3+ caused by atmospheric oxygen, while the Rb+ ion exchange only slightly alters the oxidation state of the layer manganese atoms. The absorption of Cs+ by KMS-1 follows the Langmuir model with a high exchange capacity of 226(4) mg/g (pH ≈ 7) and distribution coefficients as high as 2 × 104 mL/g. KMS-1 displays significant cesium uptake both under strongly acidic (pH 0.7−2.6) or basic conditions (pH 10−12). The kinetics of Cs+ capture by KMS-1 is fast (>90% removal of ∼1 ppm of Cs+ within only 5 min). KMS-1 was also found capab...

Highly Efficient and Rapid Cs+ Uptake by the Layered Metal Sulfide K2xMnxSn3−xS6 (KMS-1)

A new layered oxypnictide (Fe2P2)(Sr4Sc2O6) have been synthesized by solid-state reaction. This material has an alternating layer stacking structure of anti-fluorite Fe2P2 and perovskite-based Sr4Sc2O6 oxide layers. Space group of the material is P4/nmm and lattice constants a and c are 4.016 A and 15.543 A, respectively. The interlayer Fe-Fe distance corresponding to the c-axis length is the longest ever reported in the iron-based oxypnictide systems. In both magnetization and resistivity measurements, the present compound exhibited superconductivity below 17 K, which is much higher than that of LaFePO and the highest in arsenic-free iron-based oxypnictide systems under ambient pressure.

A series of layered oxychalcogenide and oxypnictide solids is described that contain oxide layers separated by distinct layers, which contain the softer chalcogenide (S, Se, Te) or pnictide (P, As, Sb, Bi) anions. The relationships between the crystal structures adopted by these compounds are described, and the physical and chemical properties of these materials are related to the structures and the properties of the elements. The properties exhibited by the oxychalcogenide materials include semiconductor properties, for example, in LaOCuCh (Ch = chalcogenide) and derivatives, unusual magnetic properties exhibited by the class Sr2MO2Cu2−δS2 (M = Mn, Co, Ni), and redox properties exhibited by the materials Sr2MnO2Cu2m−0.5Sm+1 (m = 1−3) and Sr4Mn3O7.5Cu2Ch2 (Ch = S, Se). Recent results in the oxychalcogenide area are reviewed, and some new results on the intriguing series of compounds Sr2MO2Cu2−δS2 (M = Mn, Co, Ni) are reported. Oxypnictides have received less recent attention, but this is changing: a new f...

Structures, physical properties, and chemistry of layered oxychalcogenides and oxypnictides.

Topochemical reaction strategies offer an important low-temperature (<500 °C) approach to the conscious manipulation of various inorganic host materials, allowing access to compounds that cannot be prepared by standard high-temperature methods. As the utility of these strategies continues to expand, researchers will be able to more effectively target materials with technologically significant properties. This Progress Report presents recent advances in topochemical reaction strategies as applied to perovskite and perovskite-related compounds. Emphasis is placed on structural modifications and corresponding variations in properties. Additionally, the future prospects of this approach to the rational design of intricate target compounds are discussed.

Topochemical manipulation of perovskites: low-temperature reaction strategies for directing structure and properties.

An homologous series of layered oxysulfides Sr2MnO2Cu2m-δSm+1 with metamagnetic properties is described. Sr2MnO2Cu2-δS2 (m = 1), Sr2MnO2Cu4-δS3 (m = 2) and Sr2MnO2Cu6-δS4 (m = 3), consist of MnO2 sheets separated from antifluorite-type copper sulfide layers of variable thickness by Sr2+ ions. All three compounds show substantial and similar copper deficiencies (δ ≈ 0.5) in the copper sulfide layers, and single-crystal X-ray and powder neutron diffraction measurements show that the copper ions in the m = 2 and m = 3 compounds are crystallographically disordered, consistent with the possibility of high two-dimensional copper ion mobility. Magnetic susceptibility measurements show high-temperature Curie−Weiss behavior with magnetic moments consistent with high spin manganese ions which have been oxidized to the (2+δ)+ state in order to maintain a full Cu-3d/S-3p valence band, and the compounds are correspondingly p-type semiconductors with resistivities around 25 Ω cm at 295 K. Positive Weiss temperatures in...

http://ematweb.cmi.ua.ac.be/emat/pdf/1374.pdf

Timothy P. Overton

Papers

Structural Chemistry and Metamagnetism of an Homologous Series of Layered Manganese Oxysulfides