Production of Thin PbxSn1–xTe Films by “Hot Wall” Method for Creating IR-Photodetectors

Alloys of lead and tin telluride (PbxSn1–xTe) are materials with good thermoelectric properties, as well as semiconductors that can be used as long-wave infrared detectors. Polycrystalline telluride of PbxSn1–xTe (0.05 £ x £ 0.80) alloys has been synthesized by direct fusion technique. Thin films of these materials have been obtained by the hot wall method depositing Сorning 7059 on glass substrates at Tsub = (200–350) oC and vacuum of about 10–5 Torr. The microstructure of the films has been investigated by XRD, SEM and EDX methods. The X-ray spectra of thin films have been in satisfactorily agreement with the spectra of the powder target and indicated the absence of binary phases. The films have shown a natural cubic crystalline structure. While increasing the lead content, the unit cell parameter of the crystal also increases. The established linear relationship between the unit cell parameter and the elemental composition corresponds to Vegard's law. The SEM analysis has shown that the films are polycrystalline, have a columnar structure, are tightly packed and have good mechanical adhesion. The grain size depends on the chemical composition and temperature of the substrate. The electrical measurements have shown that the grown films are non-degenerate semiconductors of p-type conductivity. The conductivity of the films was in the range of σ = (3 × 101)–(1 × 104) Ω–1×cm–1. An increase of lead concentration leads to a decrease in electrical conductivity. Hall mobility in the grown thin films increases in the range of changes in the lead content from ~10 to ~23 at. %, and decreases with a further increase to ~33 at. %. At the same time, the strongest dependence of the decrease in mobility on an increase in temperature increase is observed for films with a high lead content and is explained by the predominant scattering of charge carriers by vibrations of the crystal lattice. For a sample with an average lead concentration, an alternative effect of two scattering mechanisms is observed in the temperature dependence of the mobility: by impurity ions and by phonons.

Crystal Structure of an Anisotropic Pyrope Garnet That Contains Two Cubic Phases

The crystal structure of two different samples of pyrope garnet, ideally Mg3Al2Si3O12, from South Africa was refined using the Rietveld method, space group Ia3¯d, and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Sample 1 from Wesselton Mine is a single cubic phase and is optically isotropic. Electron-probe microanalysis (EPMA) provided an average composition {Mg2.30Fe2+0.26Ca0.42Mn2+0.02}∑3[Al1.53Fe3+0.06Cr3+0.40Ti4+0.01Fe2+0.01]∑2Si3O12, which contains a significant amount of Cr cations. The unit-cell parameter (Å) and bond distances (Å) are a = 11.56197(1) Å, average <Mg-O> = 2.2985, Al-O = 1.9101(4), and Si-O = 1.6343(3) Å. Sample 2 from De Beers Diamond Mine has an average composition {Mg2.33Fe2+0.33Ca0.33Mn2+0.01}∑3[Al1.73Fe3+0.12Cr3+0.06Ti4+0.05Fe2+0.05]∑2Si3O12 and is a fine-scale intergrowth of two cubic phases. The weight percentage, unit-cell parameter (Å), and bond distances (Å) for phase 2a are 62.2(1)%, a = 11.56185(1) Å, average <Mg-O> = 2.3006, Al-O = 1.9080(4), Si-O = 1.6334(4) Å. The corresponding values for phase 2b are 37.8(1)%, a = 11.53896(1) Å, average <Mg-O> = 2.2954, Al-O = 1.9020(6), Si-O = 1.6334(6) Å. The two cubic phases in sample 2 cause the crystal to be optically anisotropic because of strain induce birefringence. The unit-cell parameter and bond distances for sample 1 are similar to those in phase 2a.

Coarse-crystalline pyrite of the Central Timan

The results of mineralogical, geochemical, X-ray, isotopic and spectroscopic studies of coarse-crystalline pyrite (Kyvvozh Formation, Dimtem’el Creek, Central Timan) are presented. Pyrite is characterized by cubic habit and zonal Co distribution. It contains galena, thorite, zircon, monazite, rutile, chlorite, muscovite, quartz, albite, apatite and calcite inclusions. The unit cell parameter of pyrite vary from 5.4137 ± 0.0002 to 5.4187 ± 0.0010 A and correspond to an ideal pyrite. The sulfur isotopic composition of coarse-crystalline pyrite of 15.8‰ indicates its formation as a result of sulfate reduction during epigenesis.

The Formation of Cr-Al Spinel under a Reductive Atmosphere

In the present work, for the first time, the possibility of formation of CrAl2O4 was shown from the equimolar mixture of co-precipitated Al2O3 and Cr2O3 oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl2O4 is not stable under ambient conditions and easily undergoes oxidation to α-Al2O3 and α-Cr2O3. The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed.

Crystal-chemistry of sulfates from the Apuan Alps (Tuscany, Italy). VI. Tl-bearing alum-(K) and voltaite from the Fornovolasco mining complex

Thallium-bearing samples of alum-(K) and voltaite from the Fornovolasco mining complex (Apuan Alps, Tuscany, Italy) have been characterized through X-ray diffraction, chemical analyses, micro-Raman, infrared (FTIR), Mössbauer, and X-ray absorption spectroscopy (XAS). Alum-(K) occurs as anhedral colorless grains or rarely as octahedral crystals, up to 5 mm. Electron-microprobe analysis points to the chemical formula (K0.74Tl0.10)Σ0.84(Al0.84Fe0.14)Σ0.98S2.03O8·12H2O. The occurrence of minor NH4+ was detected through FTIR spectroscopy. Its unit-cell parameter is a = 12.2030(2) Å, V = 1817.19(9) Å3, space group Pa3. Its crystal structure has been refined down to R1 = 0.0351 for 648 reflections with Fo &gt; 4σ(Fo) and 61 refined parameters. The crystal structure refinement agrees with the partial substitution of K by 12 mol% Tl. This substitution is confirmed by XAS data, showing the presence of Tl+ having a first coordination shell mainly formed by 6 O atoms at 2.84(2) Å. Voltaite occurs as dark green cubic crystals, up to 1 mm in size. Voltaite is chemically zoned, with distinct domains having chemical formula (K1.94Tl0.28)Σ2.22(Fe3.572+Mg0.94Mn0.55)Σ5.06Fe3.063+Al0.98S11.92O48·18H2O and (K2.04Tl0.32)Σ2.36(Fe3.832+Mg0.91Mn0.29)Σ5.03Fe3.053+Al0.97S11.92O48·18H2O, respectively. Infrared spectroscopy confirmed the occurrence of minor NH4+ also in voltaite. Its unit-cell parameter is a = 27.2635 Å, V = 20265(4) Å3, space group Fd3c. The crystal structure was refined down to R1 = 0.0434 for 817 reflections with Fo &gt; 4σ(Fo) and 87 refined parameters. The partial replacement of K by Tl is confirmed by the structural refinement. XAS spectroscopy showed that Tl+ is bonded to six O atoms, at 2.89(2) Å. The multi-technique characterization of thallium-bearing alum-(K) and voltaite improves our understanding of the role of K-bearing sulfates in immobilizing Tl in acid mine drainage systems, temporarily avoiding its dispersion in the environment.

Minerály řady ullmannit - gersdorffit v asociaci s milleritem z haldy dolu Lill v Příbrami (Česká republika)

Minerals of the ullmannite–gersdorffite solid-solution was found at mine dump material from the Lill mine, the Černojamské ore deposit, Příbram, central Bohemia, Czech Republic. It forms grey groups of idiomorphic crystals up to 0.5 mm across with metallic luster on millerite crystals. It is strongly chemically zoned, from As-rich ullmannite to gersdorffite with variable Sb contents. Its unit-cell parameter, a 5.7728(13) Å and V 192.37(7) Å3, was refined from single-crystal X-ray data. Groups of acicular millerite crystals up to 4 mm in length and formula (Ni0.97Co0.03)Σ1.00S1.01 and very rare siegenite grains up to 80 μm and formula Co1.00(Ni1.66Co0.24Fe0.02)Σ1.92S4.09 were found in association.

Packing polymorphism in the structure oftrans-aqua[N,N′-bis(salicylidene)ethane-1,2-diamine-κ4O,N,N′,O′]chloridomanganese(III) monohydrate

The crystal structure of the title complex (systematic name:trans-aquachlorido{2,2′[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato-κ4O,N,N′,O′}manganese(III) monohydrate), [Mn(C16H14N2O2)Cl(H2O)]·H2O has been reported previously in the space groupP21/n[Panjaet al.(2003).Polyhedron,22, 1191–1198]. We obtained the same hydrated complex through an alternative synthesis, and crystallized a new polymorph, in the space groupP21. The molecular conformation of the complex is virtually unmodified, but the absence of the glide plane in the new polymorph halves the unit-cell parameterc, affording a non-centrosymmetric crystal structure withZ= 2, while the previously reported crystal is centrosymmetric withZ= 4. Both phases represent a case of packing polymorphism, similar to other dimorphic crystal structures retrieved from the Cambridge Structural Database.

Crystal structures of two thiazolidinone derivatives bearing a trichloromethyl substituent at the 2-position

The title compounds 2-trichloromethyl-3-phenyl-1,3-thiazolidin-4-one (C10H8Cl3NOS),1and 3-(4-chlorophenyl)-2-trichloromethyl-1,3-thiazolidin-4-one (C10H7Cl4NOS)2, are structurally related with one atom substitution difference in theparaposition of the benzene ring. In both structures, the thiazolidinone ring adopts an envelope conformation with the S atom as the flap. The dihedral angles between the rings [48.72 (11) in1and 48.42 (9)° in2] are very similar and the molecules are almost superimposable. In both crystal structures, C—H...O `head-to-tail' interactions between the chiral carbon atoms and the thiazolidinone oxygen atoms result in infinite monochiral chains along the direction of the shortest unit-cell parameter, namelyain1andbin2. C—H...π interactions between the thiazolidinone carbon atom at the 4-position and the phenyl ring of the neighboring enantiomer also help to stabilize the packing in each case, although the crystals are not isostructural.

Dynamics of the crystal structure of tin-based type-I clathrates with different degrees of disorder in their cationic frameworks

The temperature dependencies of heat capacity and cubic unit cell parameter for type-I clathrates were obtained to determine the influence of the concentration of vacancies and substituting atoms on the lattice dynamics.