High-pressure Synthesis of New layered Oxyhalide Perovskites

The development of transition metal oxides with perovskite-based structure has stimulated the search for mixed anion systems such as oxynitrides, oxyhalides and oxysulfides because incorporation of two different anions in one structure offers further opportunity to effectively induce chemical and physical properties that the pure oxides cannot possess. Such mixed anion phases, however, are difficult to be synthesized by a conventional high-temperature reaction. In this study, we have employed a high pressure technique to overcome this issue, and succeessfully synthesized a series of new layered oxhalide compounds. We present structural and magnetic properties of high-valent nickel oxyhalides Sr2NiO3X (X = F, Cl), and square-planar coordinated oxychlorides Sr2MO2Cl2 (Mn, Ni) and Ba2PdO2Cl2, isostructural with superconducting parent compund Ca2CuO2Cl2.

Self-Assembly of Block Copolymers - from Periodic to Aperiodic Structures

Block copolymers with incompatible components are known to self-assemble into regular structures with mesoscopic length scales. This paper introduces periodic and aperiodic tiling structures from two kinds of three component terpolymer systems. One includes binary blends of linear poly(isoprene-styrene-2-vinylpyridine)(ISP) triblock terpolymers with cylindrical structures. When average composition of a blend is a little off from symmetry, i.e., composition ratio of three components are 0.24/0.59/0.17 for I/S/P, the system show unusual cylindrical array, where gray P domain has 5 black I domain neighbors, however it has found this structure is a periodic one with hexagonal symmetry. The other system is star-shaped terpolymers from the same polymer species, that is polyisoprene(I), polystyrene(S) and poly(2-vinylpyridine)(P). It was clarified that if composition ratio is in the vicinity of 1/1/1 for I/S/P, terpolymers tend to exhibit cylindrical structures whose cross sections possess the feature of regular two-dimensional tilings, that is, Archimedean tilings. However, when the ratio is varied to some extent, the structure formed deviates from regular tiling, and finally the sample, I1S2.7P2.5, was confirmed to show quasicrystalline tiling with dodecagonal symmetry as also verified by X-ray diffraction experiments.[1]

Crystal Chemistry and Physics of Perovskites with Small Cations at the A Site

Synthesis, crystal chemistry, and physics of perovskites with small cations at the A site are an emerging field in perovskite science. Properties of ABO3 perovskites with small cations at the A site (A = Sc and In; B = transition metals) will be reported. ScBO3 and InBO3 perovskites extend the corresponding families of perovskites with A = Y, La-Lu, and Bi and exhibit larger structural distortions. As a result of large distortions, they show, in many cases, distinct structural and magnetic properties. It is manifested in B-site-ordered monoclinic structures of ScMnO3 [Inorg. Chem. 52 (2013) 9692] and `InMnO3' [Angew. Chem.: Inter. Ed. 49 (2010) 7723]; an unusual superstructure of ScRhO3 and InRhO3 [Inorg. Chem. 52 (2013) 12005]; two magnetic transitions in ScCrO3 and InCrO3 with very close transition temperatures [Chem. Mater. 24 (2012) 2197]; and antiferromagnetic ground states and multiferroic properties of Sc2NiMnO6 and In2NiMnO6 [Inorg. Chem. 52 (2013) 14108]. Features of such perovskites, such as, transition metal doping into the A site, (Sc1-xBx)BO3, will be discussed. Special attention will be given to new spin-driven multiferroics Sc2NiMnO6 and In2NiMnO6.