Sr3(Al3+xSi13−x)(N21−xO2+x):Eu2+ (x ∼ 0): a monoclinic modification of Sr-sialon

The structure of the title compound, Sr-bearing oxonitrido­aluminosilicate (Sr-sialon), contains two types of channels running along the a axis, with the three unique Sr atoms (coordinatioon number seven) residing in the larger one. The channels cross a three-dimensional Si–Al–O–N network, in which the Si and Al atoms are in a tetra­hedral coordination with N and O atoms. The chemical composition of the crystal is close to Sr3Al3Si13N21O2 (tris­trontium trialuminium trideca­silicon henicosa­nitride dioxide), which can be expressed as a mixture of SrSiN2, Si3N4, AlN, and SiO2 components in the molar ratio 3:3:3:1. The crystal studied was metrically orthorhombic, consisting of four twin components related by metric merohedry

Apatite-type SrPr4(SiO4)3O

Single crystals of the title compound, strontium tetra­praseo­dymium tris­(silicate) oxide, SrPr4(SiO4)3O, have been grown by the self-flux method using SrCl2. The structure is isotypic with the apatite supergroup family having the generic formula IX M12 VII M23(IV TO4)3 X, where M = alkaline earth and rare earth metals, T = Si and X = O. The M1 site (3.. symmetry) is occupied by Pr and Sr atoms with almost even proportions and is surrounded by nine O atoms forming a tricapped trigonal prism. The M2 site (m.. symmetry) is almost exclusively occupied by Pr and surrounded by seven O atoms, forming a distorted penta­gonal bipyramid. The Si atom (m.. symmetry) is surrounded by two O (m.. symmetry) and two O atoms in general positions, forming an isolated SiO4 tetra­hedron. Another O atom at the inversion centre (.. symmetry) is surrounded by three M2 sites, forming an equilateral triangle perpendicular to the c axis

(CaxNd11-x)Ru4O24 (x = 4.175)

Single crystals of the title compound, calcium neodymium ruthenate, (CaxNd11-x)Ru4O24 (x = 4.175), have been grown by the flux method. The structure consists of two crystallographically independent RuO6 octa­hedra, which are isolated from each other and embedded in a matrix composed of the Ca and Nd atoms. There are seven M sites which accommodate the Ca and Nd atoms with different populations. Four M sites at general positions are enriched with Nd, whereas the remaining three M sites on twofold rotation axes are enriched with Ca. The coordination numbers of O atoms to the M sites range from 6 to 9. The mean oxidation state of Ru was estimated at +4.79 from the composition analysis. The title compound is non-centrosymmetric and potentially multiferroic

新刊紹介

[新刊紹介] Book Reviewp.44, p.58, p.66, pp.73-74, pp.85-86, p.102, pp.109-110, p.117, p.123, pp.127-12

K-site splitting in KTiOPO4 at room temperature

The room-temperature structure of potassium titanyl phosphate (KTiOPO4, KTP) with Pna2(1) symmetry has been studied by means of synchrotron radiation. Each of the two crystallographically unique K1 and K2 cations is split over two sites that are shifted along the c direction by 0.287 (13) and 0.255 (13) angstrom for the K1a/b and K2a/b pairs, respectively. The refined populations of the minor K1b and K2b sites are 0.102 (12) and 0.132 (17), respectively. It is shown that accurate high-resolution synchrotron data (R-merged=0.015 for 25010 reflections, 9456 unique, sin theta/lambda limit>1.0) are required for the determination of a reliable structure model

K-site splitting in KTiOPO4 at room temperature

The room-temperature structure of potassium titanyl phosphate (KTiOPO4, KTP) with Pna2(1) symmetry has been studied by means of synchrotron radiation. Each of the two crystallographically unique K1 and K2 cations is split over two sites that are shifted along the c direction by 0.287 (13) and 0.255 (13) angstrom for the K1a/b and K2a/b pairs, respectively. The refined populations of the minor K1b and K2b sites are 0.102 (12) and 0.132 (17), respectively. It is shown that accurate high-resolution synchrotron data (R-merged=0.015 for 25010 reflections, 9456 unique, sin theta/lambda limit>1.0) are required for the determination of a reliable structure model