A. M. Antipin

Structure of compound Pr5Mo3O16+δ exhibiting mixed electronic—ionic conductivity

The structure of Pr5Mo3O16 + δ single crystals is studied by X-ray diffraction, EDXS microanalysis, transmission microscopy, and XANES spectroscopy. It is found that in the structure Pr and Mo cations mutually replace each other, atomic positions of oxygen are split into several additional positions, and structural voids accommodate interstitial oxygen atoms (which make the main contribution to the conductivity). The disorder of the oxygen sublattice is responsible for the continuity of the framework of the ways of migration of oxygen ions.

Structure of fluorite-like compound based on Nd5Mo3O16 with lead partly substituting for neodymium

A single crystal of Nd5Mo3O16 with lead partly substituting for neodymium, which has a fluorite-like structure, was studied by precision X-ray diffraction, high-resolution transmission microscopy and EDX microanalysis. The crystal structure is determined in the space group Pn3¯n. It was found that the Pb atoms substitute in part for Nd atoms in the structure and are located in the vicinity of Nd2 positions. Partial substitutions of Mo cations for Nd positions and of Nd for Mo positions in crystals of the Ln5Mo3O16 oxide family are corroborated by X-ray diffraction for the first time. The first experimental verification of the location of an additional oxygen ion in the voids abutting MoO4 tetrahedra was obtained.

Single-crystal structure of Nd{sub 5}Mo{sub 3}O{sub 16} at T = 30 K

A precision X-ray diffraction study of Nd5Mo3O16 single crystals is performed for the first time at 30 K. Measurements in the range from room temperature to 30K showed that the unit-cell parameters and volume change smoothly. The crystal structure at T = 30 K is similar to that at room temperature. The model of splitting of the atomic positions is confirmed.

Single-crystal structure of Nd5Mo3O16 at T = 30 K

A precision X-ray diffraction study of Nd5Mo3O16 single crystals is performed for the first time at 30 K. Measurements in the range from room temperature to 30K showed that the unit-cell parameters and volume change smoothly. The crystal structure at T = 30 K is similar to that at room temperature. The model of splitting of the atomic positions is confirmed.

Single-crystal structure of vanadium-doped La2Mo2O9

A high-precision X-ray diffraction study of single crystals of two compositions—La2Mo1.78V0.22O8.89 and La2Mo1.64V0.36O8.82—was performed. In the vanadium-doped compounds, as in the structure of the metastable βms phase of pure La2Mo2O9, the La and Mo atoms and one of the three oxygen atoms are displaced from the threefold axis, on which they are located in the high-temperature β phase. The structure contains two partially occupied oxygen sites. It was shown that molybdenum atoms are partially replaced by vanadium atoms, which are not involved in the disordering, are located on the threefold axis, and are shifted toward one of the oxygen atoms. This is consistent with the temperature-induced changes in the structure of La2Mo2O9 and the changes in the properties of these crystals caused by the introduction of vanadium atoms into the structure.

Growth and structure of K{sub 2}Ni{sub x}Co{sub (1–x)}(SO{sub 4}){sub 2} · 6H{sub 2}O single crystals

Single crystals of the K2NixCo(1–x)(SO4)2 · 6H2O composition are grown by spontaneous flux crystallization. More exact chemical formulas of the single crystals are determined based on the diffraction data as K2Co(SO4)2 · 6H2O (I), K2(Co0.657Ni0.343)(SO4)2 · 6H2O (II), K2(Co0.226Ni0.774)(SO4)2 · 6H2O (III), K2(Co0.216Ni0.784)(SO4)2 · 6H2O (IV), and K2Ni(SO4)2 · 6H2O (V). The substitution of nickel atoms for cobalt atoms in structure I results in a shortening of all (Co,Ni)–O interatomic distances. With increasing Ni concentration, the (Co,Ni)–O2 distance shortens to a lesser degree than the (Co,Ni)–O1 and (Co,Ni)–O3 distances and, as a consequence, the distortion of (Co,Ni)O6 octahedra decreases. NiO6 polyhedra are less distorted than CoO6 octahedra. The analysis of difference syntheses of electron density shows that the number of uninterpretable peaks on the maps of mixed crystals II, III, and IV, as well as on the map of K2Co(SO4)2 · 6H2O, is larger with respect to those of structure K2Ni(SO4)2 · 6H2O.Single crystals of the K{sub 2}Ni{sub x}Co{sub (1–x)}(SO{sub 4}){sub 2} · 6H{sub 2}O composition are grown by spontaneous flux crystallization. More exact chemical formulas of the single crystals are determined based on the diffraction data as K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O (I), K{sub 2}(Co{sub 0.657}Ni{sub 0.343})(SO{sub 4}){sub 2} · 6H{sub 2}O (II), K{sub 2}(Co{sub 0.226}Ni{sub 0.774})(SO{sub 4}){sub 2} · 6H{sub 2}O (III), K{sub 2}(Co{sub 0.216}Ni{sub 0.784})(SO{sub 4}){sub 2} · 6H{sub 2}O (IV), and K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O (V). The substitution of nickel atoms for cobalt atoms in structure I results in a shortening of all (Co,Ni)–O interatomic distances. With increasing Ni concentration, the (Co,Ni)–O2 distance shortens to a lesser degree than the (Co,Ni)–O1 and (Co,Ni)–O3 distances and, as a consequence, the distortion of (Co,Ni)O{sub 6} octahedra decreases. NiO{sub 6} polyhedra are less distorted than CoO{sub 6} octahedra. The analysis of difference syntheses of electron density shows that the number of uninterpretable peaks on the maps of mixed crystals II, III, and IV, as well as on the map of K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O, is larger with respect to those of structure K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O.

Growth and structure of K2NixCo(1–x)(SO4)2 · 6H2O single crystals

Single crystals of the K2NixCo(1–x)(SO4)2 · 6H2O composition are grown by spontaneous flux crystallization. More exact chemical formulas of the single crystals are determined based on the diffraction data as K2Co(SO4)2 · 6H2O (I), K2(Co0.657Ni0.343)(SO4)2 · 6H2O (II), K2(Co0.226Ni0.774)(SO4)2 · 6H2O (III), K2(Co0.216Ni0.784)(SO4)2 · 6H2O (IV), and K2Ni(SO4)2 · 6H2O (V). The substitution of nickel atoms for cobalt atoms in structure I results in a shortening of all (Co,Ni)–O interatomic distances. With increasing Ni concentration, the (Co,Ni)–O2 distance shortens to a lesser degree than the (Co,Ni)–O1 and (Co,Ni)–O3 distances and, as a consequence, the distortion of (Co,Ni)O6 octahedra decreases. NiO6 polyhedra are less distorted than CoO6 octahedra. The analysis of difference syntheses of electron density shows that the number of uninterpretable peaks on the maps of mixed crystals II, III, and IV, as well as on the map of K2Co(SO4)2 · 6H2O, is larger with respect to those of structure K2Ni(SO4)2 · 6H2O.Single crystals of the K{sub 2}Ni{sub x}Co{sub (1–x)}(SO{sub 4}){sub 2} · 6H{sub 2}O composition are grown by spontaneous flux crystallization. More exact chemical formulas of the single crystals are determined based on the diffraction data as K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O (I), K{sub 2}(Co{sub 0.657}Ni{sub 0.343})(SO{sub 4}){sub 2} · 6H{sub 2}O (II), K{sub 2}(Co{sub 0.226}Ni{sub 0.774})(SO{sub 4}){sub 2} · 6H{sub 2}O (III), K{sub 2}(Co{sub 0.216}Ni{sub 0.784})(SO{sub 4}){sub 2} · 6H{sub 2}O (IV), and K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O (V). The substitution of nickel atoms for cobalt atoms in structure I results in a shortening of all (Co,Ni)–O interatomic distances. With increasing Ni concentration, the (Co,Ni)–O2 distance shortens to a lesser degree than the (Co,Ni)–O1 and (Co,Ni)–O3 distances and, as a consequence, the distortion of (Co,Ni)O{sub 6} octahedra decreases. NiO{sub 6} polyhedra are less distorted than CoO{sub 6} octahedra. The analysis of difference syntheses of electron density shows that the number of uninterpretable peaks on the maps of mixed crystals II, III, and IV, as well as on the map of K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O, is larger with respect to those of structure K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O.

Software for HUBER-5042 Diffractometer with Displex DE-202 Helium Cryostat

A software for structural studies on a Huber-5042 diffractometer with a point detector and closed-cycle Displex DE-202 helium cryostat has been developed. The software package includes programs for the preliminary stage of experiment, planning, data collection, profile analysis of reflections, etc. The measurement of reflections in the 2θ angular range from 0° to 152° is provided, which is unique for Eulerian goniometers. Tools for enhancing data collection are demonstrated. Accurate experimental data are obtained for a test CaF2 crystal (sp. gr.

X-ray diffraction study of oxygen-conducting compounds Ln₂Mo₂O₉ (Ln = La, Pr).

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