Space Group R3m Research Articles

Low temperature liquid phase growth of crystalline InSe grown by the temperature difference method under controlled vapor pressure

Indium selenide (InSe), which is one of the most promising layered III-chalcogenide compounds, is an attractive material for applications in infrared detection, solar energy conversion and high mobility transfer devices etc. In this work, InSe crystals were grown from the liquid phase using the temperature difference method under controlled vapor pressure (TDM-CVP) at a growth temperature of 582 °C, which is lower than that of the melt used in the Bridgman-Stockbarger technique. X-ray diffraction (XRD) and Raman spectroscopy results indicate that the grown crystal was γ-InSe with R3m space group symmetry. Photoluminescence measurements were carried out to determine the optical properties of the grown crystal, from which it was confirmed that the sample had a direct bandgap of 1.32 eV, an indirect bandgap of 1.28 eV and an exciton binding energy of 20 meV.

Synthesis and Characterization of Zn doped Li(Li0.21Mn0.54Ni0.125Co0.125)O2 as the Layer Materials For Battery Applications

In this paper, pure and impure nanopowders of Li(Li0.021Mn0.54Ni0.125Co0.125)O2 were prepared with different percentages (x=0.02%, 0.05%, 0.075%, 0.10%) of Zn impurity by sol-gel method, and the effect of different percentages were investigated on the structural, physical and chemical properties of the samples. These properties of samples characterized by X-ray diffraction (XRD), field-scattering microscopy (FESEM), X-ray energy spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), infrared spectroscopy (FTIR), and the results of characterization were investigation. All the reflection peaks indicate that the samples have standard α-NaFeO2 layered structure with the space group R3m, except for the super lattice ordering between 22°-25°.The FESEM images have shown that these nanoparticles have Hexagonal structures for doped and undoped nanopowders. The particle size of nanopowders in the range of 30-80 nm the chemical analysis of EDS has proven the presence of Zn in the samples. TG /DTA measurements showed weight loss in pure and impure of nanopowders. In infrared spectroscopy (FTIR), the connection bonds and chemical elements used in these nanopowders have been investigated.

Structural Investigation of P3-Type Na0.67Mn0.67Ni0.33O2 Cathode Material By X-Ray Diffraction and X-Ray Absorption Spectroscopy

The interest in lithium and sodium ion batteries is rapidly increasing with the development of electrical vehicles and hybrid electrical vehicles. Not only due to the low cost of sodium but also due to its wide distribution and abundance, sodium ion batteries are more prospective for large-scale production of stationary storage devices compared with lithium ion batteries. Among the different types of Na based cathode materials, layered NaxTMO2 (TM = Mn, Ni, Co, and Fe) cathode materials are one of the top candidates, which behave similar to layered materials for Li ion batteries. However, the phase transformation of these sodium ion cathode materials during charge and discharge process is much more complicated than that of lithium ion batteries[1-4]. P3-type Na0.67Mn0.67Ni0.33O2 (NMNO) synthesized by solid-state reaction method at 700 ˚C for 12 hours is a promising cathode material for sodium ion batteries due to its low production temperature compared with P2-type NMNO. Additionally, the capacity of P3-type NMNO during the first 40 cycles is higher than that of P2-type NMNO. In order to understand the electrochemical performance of P3-type NMNO and its related practical use as cathode material, it is urgently necessary to investigate the details of the structure and redox reaction of P3-type NMNO. We, therefore, used X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) to investigate the structure and oxidation state, respectively, of Ni and Mn ions at different stages of charge/discharge. The XRD pattern of P3-type NMNO was refined with the small hexagonal cell (R3m space group, a=b=2.886 Å and c=16.780 Å). Fig. 1 shows the normalized Mn (a) and Ni (b) K-edge X-ray absorption near edge spectra (XANES) at the first charge and discharge process. One can see an energy shift of Ni K-edge to higher energy after charge to 4.5 V and a shift back to the position of the pristine material after discharge to 1.5 V. This means the average valence of Ni increases during the charge process and then decreases to lower valence state during discharge. However, the energy shift of Mn K-edge is much smaller during the first cycle indicating Ni ions are the main part of redox reaction, while Mn ions participate only to minor extend in the redox reaction. This behavior can be also proved by the extended X-ray absorption fine spectra (EXAFS) after Fourier transform. The Ni-O bonding length decreases after charging to 4.5 V and then increases after discharge to 1.5 V indicating a change of average valence of Ni ions which affects the attraction between nickle ions and the coordinated oxygen ions. However, the Mn-O bonding length was almost immutably during the first cycle. The changes in disorder of P3-type NMNO and changes of the number of neighboring atoms surrounding Ni or Mn ions during charge and discharge process lead to the variation of peak intensities of the Ni and Mn EXAFS spectra.

Siudaite, Na8(Mn2+2Na)Ca6Fe3+3Zr3NbSi25O74(OH)2Cl·5H2O: a new eudialyte-group mineral from the Khibiny alkaline massif, Kola Peninsula

The new eudialyte-group mineral siudaite, ideally Na8(Mn2+2Na)Ca6Fe3+3Zr3NbSi25O74(OH)2Cl·5H2O, was discovered in a peralkaline pegmatite situated at the Eveslogchorr Mt., Khibiny alkaline massif, Kola Peninsula, Russia. The associated minerals are aegirine, albite, microcline, nepheline, astrophyllite, and loparite-(Ce). Siudaite forms yellow to brownish-yellow equant anhedral grains up to 1.5 cm across. Its lustre is vitreous, and the streak is white. Cleavage is none observed. The Mohs’ hardness is 4½. Density measured by hydrostatic weighing is 2.96(1) g/cm3. Density calculated using the empirical formula is equal to 2.973 g/cm3. Siudaite is nonpleochroic, optically uniaxial, negative, with ω = 1.635(1) and e = 1.626(1) (λ = 589 nm). The IR spectrum is given. The chemical composition of siudaite is (wt%; electron microprobe, H2O determined by HCN analysis): Na2O 8.40, K2O 0.62, CaO 9.81, La2O3 1.03, Ce2O3 1.62, Pr2O3 0.21, Nd2O3 0.29, MnO 6.45, Fe2O3 4.51. TiO2 0.54, ZrO2 11.67, HfO2 0.29, Nb2O5 2.76, SiO2 47.20, Cl 0.54, H2O 3.5, –O = Cl − 0.12, total 99.32. According to Mossbauer spectroscopy data, all iron is trivalent. The empirical formula (based on 24.5 Si atoms pfu, in accordance with structural data) is [Na7.57(H2O)1.43]Σ9(Mn1.11Na0.88Ce0.31La0.20Nd0.05Pr0.04K0.41)Σ3(H2O)1.8(Ca5.46Mn0.54)Σ6(Fe3+1.76Mn2+1.19)Σ2.95Nb0.65(Ti0.20Si0.50)Σ0.71(Zr2.95Hf0.04Ti0.01)Σ3Si24.00Cl0.47O70(OH)2Cl0.47·1.82H2O. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3m, with a = 14.1885(26) A, c = 29.831(7) A, V = 5200.8(23) A3 and Z = 3. Siudaite is chemically related to georgbarsanovite and is its analogue with Fe3+-dominant M2 site. The strongest lines of the powder X-ray diffraction pattern [d, A (I, %) (hkl)] are: 6.38 (60) (–114), 4.29 (55) (–225), 3.389 (47) (131), 3.191 (63) (–228). 2.963 (100) (4–15), 2.843 (99) (–444), 2.577 (49) (3–39). Siudaite is named after the Polish mineralogist and geochemist Rafal Siuda (b. 1975).

Effect of Nd Doping on Dielectric and Impedance Properties of PZT Nanoceramics

Neodymium-doped lead zirconate tianate, i.e. Pb1−xNd x Zr0.52Ti0.48O3 (PNZT) ceramics, with x = 0–10 mol.% has been prepared by the sol–gel process. X-ray diffraction pattern at room temperature shows the pyrochlore free phase for all samples. The structural analysis suggests the coexistence of both rhombohedral (R3m space group) and tetragonal (P4 mm space group) crystal symmetries. Scanning electron micrographs of the samples show uniform distribution of grain and grain boundaries. Dielectric constant increases with the increase in neodymium concentration in the crystal lattice. Degree of diffuse phase transition increases with the increase in Nd3+ concentration in the sample. Nd3+ incorporation into the lead zirconatetitanate (PZT) lattice enhances the spreading factor. Interaction between neighbouring dipoles decreases with the increase of Nd3+ in PZT lattice. The conduction mechanism of the sample can be attributed to the overlapping large polar tunnelling. Second-order dielectric phase transition has been observed at the Curie temperature. The electrical properties of the sample can be explained by considering grain and grain boundaries contributions. All the samples show the poly-dispersive non-Debye type relaxation.

Structural, Morphological and Temperature Dependent Dielectric Studies of Sr-Cu Nano Sized Hexa Ferrites

A series of polycrystalline SrCu nano ferrites substituted with Sn-Co having generic formula Sr2Cu2Fe12-X(SnCo)X/2O22 (where x changes from 0 to 2.5 in equal steps of 0.5) have been synthesized by novel microwave assisted sol gel process using urea as fuel. Structural characterization of the prepared compounds have been performed using X-ray powder diffraction pattern, which shows formation of single Y-type hexagonal phase and belonging to space group R3-m(no.166). The lattice parameters, X-ray density (Dx), measured density (Dm), and porosity (P) of samples are calculeted from XRD data. We observed that the lattice parameters “a” and “c” increasewith content of SnCo. The crystallite size is in the range 13- 47nm, shows nanometer size of prepared compounds. The microstructure is studied by transmission electron microscopy (TEM).The ac electrical conductivity (σac) dielectric constant (∊’), and dielectric loss (tan δ) are studied a function of temperature. The plot of conductivity verses 1/T shows semiconducting nature of the compounds. The results of dielectric constant and dielectric loss are explained on the basis of the assumption that the mechanism of dielectric polarization is similar to that of conduction process.

Li(Ni,Co,Al)O2 Cathode Delithiation: A Combination of Topological Analysis, Density Functional Theory, Neutron Diffraction, and Machine Learning Techniques

Here we have combined topological analysis, density functional theory (DFT) modeling, operando neutron diffraction, and machine learning algorithms within the comparative analysis of the known widely LiNiO2 (LNO) and LiNi0.8Co0.15Al0.05O2 (NCA) cathode materials. Full configurational spaces of the mentioned materials during delithiation were set using the topological approach starting from the 2 × 2 × 1 supercell (12 formula units in total) of the LNO structure (space group R3m). Several types of the DFT models were applied for the structural relaxation of entries of the LNO configurational space (87 configurations) demonstrating a strong dependence of the results of optimization on the initial structure guess (at the latter delithiation stages) and on the Hubbard correction application (for the whole range of delithiation). Within the computationally easiest model considered for LNO, subsequent modeling of the NCA configurational space (20760 configurations) results in structural changes of the model ce...

Effects of Fluorine and Chromium Doping on the Performance of Lithium-Rich Li1+xMO2(M = Ni, Mn, Co) Positive Electrodes

Lithium-rich metal oxides Li1+zMO2 (M = Ni, Co Mn, etc.) are promising positive electrode materials for high-energy lithium-ion batteries, with capacities of 250–300 mAh·g–1 that closely approach theoretical intercalation limits. Unfortunately, these materials suffer severe capacity fade on cycling, among other performance issues. While ion substitution can improve the performance of many of these materials, the underlying mechanisms of property modification are not completely understood. In this work we show enhanced performance of the Li1+zMO2 electrode, consisting of Li2MnO3 (with C2/m space group) and LiMO2 (with R3m space group) phases, and establish the effects of cationic and anionic substitution on the phase and structure evolution underpinning performance changes. While the undoped material has a high capacity of ∼270 mAh·g–1, only 79% of this remains after 200 cycles. Including ∼2% Cr in the material, likely at the R3m metal (3a) site, improved cycle performance by ∼13%, and including ∼5% F in...

Crystal Chemistry of Pyroaurite from the Kovdor Pluton, Kola Peninsula, Russia, and the Långban Fe–Mn deposit, Värmland, Sweden

Pyroaurite [Mg6Fe23+ (OH)16][(CO3)(H2O)] from the Kovdor Pluton on the Kola Peninsula, Russia, and the Langban deposit in Filipstad, Varmland, Sweden were studied with single crystal and powder X-ray diffraction, an electron microprobe, and Raman spectroscopy. Both samples are rhombohedral, space group R3m, a = 3.126(3), c = 23.52(2) A (Kovdor), and a = 3.1007(9), c = 23.34(1) (Langban). The powder XRD revealed only the 3R polytype. The ratio of di- and trivalent cations M2+: M3+ was determined as ~3.1–3.2 (Kovdor) and ~3.0 (Langban). The Raman spectroscopy of the Kovdor sample verified hydroxyl groups and/or water molecules in the mineral (absorption bands in the region of 3600–3500 cm–1) and carbonate groups (absorption bands in the region of 1346–1058 cm–1). Based on the data obtained, the studied samples should be identified as pyroaurite-3R (hydrotalcite group).

KBaR(BO3)2 orthoborates (R = REE): Synthesis and study

The search for compounds with the formula composition KBaR(BO3)2 has been performed by solid-phase synthesis and differential thermal analysis. The compounds synthesized in this series are KBaPr(BO3)2 and KBaNd(BO3)2, which are isostructural to KBaY(BO3)2, are isotypical to butschliite K2Ca(CO3)2, and crystallize in a trigonal system with space group R3m. The structural characteristics of compounds calculated for the entire series of REEs are given.

The Influence of the Valence Electron Concentration on the Structural Variation of the Laves Phases MgNi2–xGex

The influence of the partial substitution of Ni atoms by the similarly sized but electron‐richer Ge atoms with a similar electronegativity in the binary Laves phase MgNi2 is investigated. A small degree of substitution in MgNi2–xGex (x = 0.1) leads to the change of the hexagonal MgNi2‐type structure (C36) to the cubic C15 type, whereas higher amounts of Ge lead to the formation of the two new Laves phases Mg2Ni3Ge and MgNi1.30(5)Ge0.70, which were synthesized by the direct reaction of the elements in alumina and niobium crucibles using an induction furnace. The crystal structures of the two phases were determined by single‐crystal X‐ray diffraction. Mg2Ni3Ge (hR18‐MgNi2–xGex, x = 0.5) crystallizes in the Y2Rh3Ge‐type structure, which is an ordered variant of the cubic Laves phase MgCu2: space group R3m, a = 5.0300(7), c = 11.330(2) Å. hP36‐MgNi2–xGex with x = 0.70(6) crystallizes as a superstructure of the hexagonal Laves phase MgZn2: space group P63/mcm, a = 8.6946(2), c = 7.8127(3) Å. MgNi1.3Ge0.7 represents a new structure type. Gradual substitution of Ni by Ge in the Laves phase MgNi2 corresponds to an increase in the valence electron concentration (VEC) in the ternary phase system and leads to the series MgCu2 (C15 type), hR18‐Mg2Ni3Ge (superstructure of MgCu2 type), and hP36‐MgNi1.3Ge0.7 (superstructure of MgZn2 type). The electronic structures are discussed based on band structure calculations, and the results are compared to the pristine Laves phase MgNi2, MgCu2, and MgZn2 with VEC = 2/3, 4/3 and 2, respectively.

Crystal Structure and Magnetic and Magnetocaloric Properties of Cobalt Hydroxychlorides Co2(OH)4–xClx

A series of isostructural cobalt hydroxychloride salts with the formula Co2(OH)4–xClx were fabricated by using a precipitation method from aqueous solutions of CoCl2 and NaOH with different mixing ratios. The crystal structure was resolved from neutron powder diffraction data, including the location of H atoms of the hydroxide groups. The structure (space group R3m) consists of an open network of edge‐sharing CoO6 and CoO6–2xCl2x octahedra, forming intercrossed 1D channels where the hydrogen atoms reside. Unusually high values of the magnetic entropy change were observed for all samples, probably due to the geometrically frustrated magnetic structure; for example, the magnetic entropy change was 8.3 J/kg K for the sample with Co/Cl > 2.5 at 10 K in a magnetic field change of 20 kOe.

Crystal structure, homogeneity range and electronic structure of rhombohedral γ-Mn5Al8

Abstract The γ-region of the Mn–Al phase diagram between 45 and 70 at.% Al was re-investigated by a combination of powder and single crystal X-ray diffraction as well as EDS analysis to establish the distribution of Mn and Al atoms. Single crystals of γ-Mn5–x Al8+x were grown using Sn-flux at 650 °C. The crystal structure, atomic coordinates and site occupancy parameters of γ-Mn5−x Al8+x phases were refined from single crystal X-ray data. The γ-Mn5-x Al8+x phase adopts the rhombohedral Cr5Al8-type structure rather than a cubic γ-brass structure. The refined compositions from two crystals extracted from the Al-rich and Mn-rich sides are, respectively, Mn4.76Al8.24(2) (I) and Mn6.32Al6.68(2) (II). The structure was refined in the acentric R3m space group (No.160, Z=6), in order to compare with other reported rhombohedral γ-brasses. In addition, according to X-ray powder diffraction analysis, at the Al-rich side the γ-phase coexists with LT–Mn4Al11 and, at the Mn-rich side, with a hitherto unknown phase. The refined lattice parameters from powder patterns fall in the range a=12.6814(7)−12.6012(5) Å and c=7.9444(2)−7.9311(2) Å from Al-rich to Mn-rich loadings, and the corresponding rhombohedral angles distorted from a pseudo-cubic cell were found to be 89.1(1)°−88.9(1)°. Magnetic susceptibility and magnetization studies of Mn4.92Al8.08(2) are consistent with moment bearing Mn and suggest a spin glass state below 27 K. Tight-binding electronic structure calculations (LMTO-ASA with LSDA) showed that the calculated Fermi level for γ-“Mn5Al8” falls within a pseudogap of the density of states, a result which is in accordance with a Hume-Rothery stabilization mechanism γ-brass type phases.

Eventual Chemical Transformation of Metals and Chalcogens into Metal Chalcogenide Nanoplates through a Surface Nucleation-Detachment-Reorganization Mechanism

Many studies have reported the synthesis of two-dimensional (2D) nanoplates and nanosheets of the layer-structured metal chalcogenides but also have reported various structures far from the 2D shape. In multicomponent compounds, the elemental concentrations keep changing during the reaction; hence, the reactions are considered to be nonstoichiometric from the nucleation and may include continuous changes in the structure and composition. The different shapes of the metal chalcogenides with the layered structure are attributed to the nonstoichiometric reactions. However, it has not been studied if such nonstoichiometric reactions eventually produce 2D nanoplates, and the mechanism involved in the transformation has not been understood. This study investigates a two-step chemical reaction as an extreme nonstoichiometric nucleation and growth. It reveals that the layer-structured metal chalcogenides (M2X3, M = Sb and Bi, X = Se and Te) with the R3m space group can be obtained by transforming premade pure ch...

Crystal Growth and Magneto-transport of Bi2Se3 Single Crystals

In this letter, we report on the growth and characterization of bulk Bi 2Se 3 single crystals. The studied Bi 2Se 3 crystals are grown by the self-flux method through the solid-state reaction from high-temperature (950 °C) melt of constituent elements and slow cooling (2 ℃/h). The resultant crystals are shiny and grown in the [00l] direction, as evidenced from surface XRD. Detailed Reitveld analysis of powder X-ray diffraction (PXRD) of the crystals showed that these are crystallized in the rhombohedral crystal structure with a space group of R3m (D5), and the lattice parameters are a = 4.14 (2), b = 4.14 (2), and c = 28.7010 (7) A. Temperature versus resistivity (ρ−T) plots revealed metallic conduction down to 2 K, with typical room temperature resistivity (ρ 300 K) of around 0.53 m Ω-cm and residual resistivity (ρ 0 K) of 0.12 m Ω-cm. Resistivity under magnetic field [ ρ(T)H] measurements exhibited large + ve magneto-resistance right from 2 to 200 K. Isothermal magneto-resistance [ ρH] measurements at 2, 100, and 200 K exhibited magneto-resistance (MR) of up to 240 %, 130 %, and 60 %, respectively, at 14 T. Further, the MR plots are nonsaturating and linear with the field at all temperatures. At 2 K, the MR plots showed clear quantum oscillations at above say 10 T applied field. Also, the Kohler plots, i.e., Δρ/ ρ oversus B/ ρ, were seen consolidating on one plot. Interestingly, the studied Bi 2Se 3 single crystal exhibited the Shubnikov-de Haas (SdH) oscillations at 2 K under different applied magnetic fields ranging from 4 to 14 T.

Lucchesiite, CaFe2+3Al6(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup

AbstractLucchesiite, CaFe32+Al6(Si6O18)(BO3)3(OH)3O, is a new mineral of the tourmaline supergroup. It occurs in the Ratnapura District, Sri Lanka (6°35'N, 80°35'E), most probably from pegmatites and in Mirošov near Strážek, western Moravia, Czech Republic, (49°27'49.38"N, 16°9'54.34"E) in anatectic pegmatite contaminated by host calc-silicate rock. Crystals are black with a vitreous lustre, conchoidal fracture and grey streak. Lucchesiite has a Mohs hardnessof ∼7 and a calculated density of 3.209 g/cm3(Sri Lanka) to 3.243 g/cm3(Czech Republic). In plane-polarized light, lucchesiite is pleochroic (O = very dark brown and E = light brown) and uniaxial (–). Lucchesiite is rhombohedral, space groupR3m,a≈ 16.00 Å,c≈ 7.21 Å,V≈ 1599.9 Å3,Z= 3. The crystal structure of lucchesiite was refined toR1 ≈ 1.5% using ∼2000 unique reflections collected with MoKα X-ray intensity data. Crystal-chemical analysis for the Sri Lanka (holotype) and Czech Republic (cotype) samples resulted in the empirical formulae, respectively:X(Ca0.69Na0.30K0.02)∑1.01Y(Fe1.442+Mg0.72Al0.48Ti0.334+V0.023+Mn0.013+Zn0.01)∑3.00Z(Al4.74Mg1.01Fe0.253+)∑6.00[T(Si5.85Al0.15)∑6.00O18](BO3)3V(OH)3W[O0.69F0.24(OH)0.07]∑1.00andX(Ca0.49Na0.45□0.05K0.01)∑1.00Y(Fe1.142+Fe0.953+Mg0.42Al0.37Mn0.03Ti0.084+Zn0.01)∑3.00Z(Al5.11Fe0.383+Mg0.52)∑6.00[T(Si5.88Al0.12)∑6.00O18](BO3)3V[(OH)2.66O0.34]∑3.00W(O0.94F0.06)∑1.00.Lucchesiite is an oxy-species belonging to the calcic group of the tourmaline supergroup. The closest end-member composition of a valid tourmaline species is that of feruvite, to which lucchesiite is ideally related by the heterovalent coupled substitutionZAl3++O1O2–↔ZMg2++O1(OH)1–. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA 2015-043).

Crystal structure of Al5O3N3(15R)

Having synthesised an AlON-bonded ceramic corundum material, Al5O3N3(15R) polytype coexisting withα-Al2O3was identified. The sample was prepared from an alumina-rich mixture of Al2O3and AlN substrates and fired at 1650 °C in a nitrogen atmosphere. Using the X-ray external standard quantitative method, one of the reaction products,α-Al2O3, was quantified. From the remaining substrates the stoichiometric composition of the second phase was calculated. The applied method of crystal structure determination consisted of three stages. In the first stage, the Le Bail method of X-ray pattern decomposition was used for the extraction of Al5O3N3(15R) diffraction lines from a two-phase diffractogram. The space group and unit-cell dimensions from the isostructural SiAl4O2N4SiAlON phase, producing the same X-ray pattern, were used as input data. Next, the direct structure determination in real space was applied for initial structural model derivation, which was followed by Rietveld refinement. The solved crystal structure of Al5O3N3(15R), except the stacking sequence, proved to be closely related to the structure of Al7O3N5(21R) polytype. The Al5O3N3(15R) is trigonal with space groupR-3m, unit-cell dimensionsa0= 3.0128 Å,c0= 41.8544 Å, and volumeV= 329.00 Å3. The model of Al5O3N3(15R) polytype structure has positional disordering in one of three (6c) Al sites, which leads to stacking faults in six tetrahedral layers. Every third tetrahedron from LR3and LR4, LR8and LR9, LR13andLR14layers is rotated by 180°.

Crystal structure of ilyukhinite, a new mineral of the eudialyte group

The crystal structure of ilyukhinite, a new mineral of the eudialyte group, is studied by X-ray diffraction. The mineral found in pegmatite bodies of the Kukisvumchorr Mountain (Khibiny alkaline complex) is characterized by low sodium content, high degree of hydration, and predominance of manganese over iron. The trigonal cell has the following parameters: a = 14.1695(6) and c = 31.026(1) A; space group R3m. The structure is refined to final R = 0.046 in the anisotropic approximation of atomic displacements using 1527F > 3σF. The idealized formula of ilyukhinite (Z = 3) is written as (H3O,Na)14Ca6Mn2Zr3Si26O72(OH)2 · 3H2O. The new mineral differs from other representatives of the eudialyte group by the predominance of both oxonium in the N positions of extra-framework cations and manganese in the М2 position centering the tetragonal pyramid.

The first lead cobalt phosphite, PbCo2(HPO3)3.

Single crystals of a new lead cobalt phosphite, PbCo2(HPO3)3, have been synthesized using mild hydrothermal techniques and characterized by X-ray diffraction analysis, SQUID magnetic measurements, IR spectroscopy, UV/vis spectroscopy, thermogravimetric analysis, and scanning electron microscopy. PbCo2(HPO3)3 crystallizes in the non-centrosymmetric (NCS) R3m space group, a = 5.3145(15) Å, c = 25.494(7) Å, V = 623.6(4) Å3. The crystal structure of PbCo2(HPO3)3 is based upon 2D heteropolyhedral blocks built up from Co2O9 octahedral dimers and HPO3 pseudo-tetrahedra. Lead cations reside in the interlayer space of the structure. Here, the NCS character results reasonably from the cooperative Pb2+ lone electron pair arrangements, by analogy to the centrosymmetric compound (NH4)2Co2(HPO3)3 with similar but disordered blocks. A local twisting of specific HPO3 groups arises due to unreasonably short HH contacts between two phosphite oxoanions. In terms of the magnetic behavior, the new PbCo2(HPO3)3 phase demonstrates weak antiferromagnetic interactions inside the Co2O9 dimers between cobalt ions as expected from the phosphite μ-O bridges.

Spectroscopic properties of MZnPO (M=Gd, Y) polycrystals doped with Nd3+ ions

MZnPO:Nd3+ (M=Gd, Y) phosphide oxides were synthesized by using the solid state reaction method. Crystal structures have been confirmed with the X-ray powder diffraction. The MZnPO crystals possess trigonal structure with a R3m space group. In these compounds, the phosphate ions (P3-) create ligands, like the oxygen ions. The M-O and Zn-P bonds are covalent.The absorption, FTIR and emission spectra, as well as the luminescence decay curves measurements were performed. Stark energy levels of the Nd3+ ions were obtained from the absorption and emission spectra. The spectroscopic quality parameter and the luminescence branching ratio of the neodymium(III) ions were estimated. The investigated crystals might find applications as the down-shifting materials, to enhance the yield of silicon solar cells.