The highly anisotropic material CsBi(4)Te(6) was prepared by the reaction of Cs/Bi(2)Te(3) around 600 degrees C. The compound crystallizes in the monoclinic space group C2/m with a = 51.9205(8) A, b = 4.4025(1) A, c = 14.5118(3) A, beta = 101.480(1) degrees, V = 3250.75(11) A(3), and Z = 8. The final R values are R(1) = 0.0585 and wR(2) = 0.1127 for all data. The compound has a 2-D structure composed of NaCl-type [Bi(4)Te(6)] anionic layers and Cs(+) ions residing between the layers. The [Bi(4)Te(6)] layers are interconnected by Bi-Bi bonds at a distance of 3.2383(10) A. This material is a narrow gap semiconductor. Optimization studies on the thermoelectric properties with a variety of doping agents show that the electrical properties of CsBi(4)Te(6) can be tuned to yield an optimized thermoelectric material which is promising for low-temperature applications. SbI(3) doping resulted in p-type behavior and a maximum power factor of 51.5 microW/cm.K(2) at 184 K and the corresponding ZT of 0.82 at 225 K. The highest power factor of 59.8 microW/cm.K(2) at 151 K was obtained from 0.06% Sb-doped material. We report here the synthesis, physicochemical properties, doping characteristics, charge-transport properties, and thermal conductivity. Also presented are studies on n-type CsBi(4)Te(6) and comparisons to those of p-type.

Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)(2).(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these new complexes are considerably greater than those of conventional solid zinc metal-organic chemical vapor deposition (MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N'-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent conducting oxide Zn-In-Sn-O (ZITO) because of its superior volatility and low melting point of 64 degrees C. ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the nominal composition of ZnIn(2.0)Sn(1.5)O(z)() were used in fabrication of polymer light-emitting diodes. These devices exhibit light outputs and current efficiencies almost 70% greater than those of ITO-based control devices.

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A series of yttrium-doped CdO (CYO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates at 410 degrees C by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties have been investigated. XRD data reveal that all as-deposited CYO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CYO thin films exhibit excellent optical transparency, with an average transmittance of >80% in the visible range. Y doping widens the optical band gap from 2.86 to 3.27 eV via a Burstein-Moss shift. Room temperature thin film conductivities of 8,540 and 17,800 S/cm on glass and MgO(100), respectively, are obtained at an optimum Y doping level of 1.2-1.3%. Finally, electronic band structure calculations are carried out to systematically compare the structural, electronic, and optical properties of the In-, Sc-, and Y-doped CdO systems. Both experimental and theoretical results reveal that dopant ionic radius and electronic structure have a significant influence on the CdO-based TCO crystal and band structure: (1) lattice parameters contract as a function of dopant ionic radii in the order Y (1.09 A) < In (0.94 A) < Sc (0.89 A); (2) the carrier mobilities and doping efficiencies decrease in the order In > Y > Sc; (3) the dopant d state has substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.

A New Thermoelectric Material: CsBi 4 Te 6 . -The title compound is obtained in quantitative yield by reaction of Cs 2 Te and Bi 2 Te 3 at 700°C (60 h). CsBi 4 Te 6 crystallizes in the monoclinic space group C2/m with Z = 8 (single crystal XRD). The structure consists of NaCl-type [Bi4 ] layers and Cs + ions residing between the layers. The anionic layers are interconnected by Bi-Bi bonds with a distance of 3.2383 Å. CsBi 4 Te 6 is a narrow gap semiconductor. The electrical properties can be tuned by doping to yield an optimized thermoelectric material which is promising for low-temperature applications. SbI3 doping results in p-type behavior and a maximum power factor of 51.5 µW/cm·K 2 at 184 K and the corresponding thermoelectric figure of merit ZT of 0.82 at 225 K. The highest power factor of 59.8 µW/cm·K 2 at 151 K is observed for the 0.06% Sb-doped material. -(CHUNG, D.-Y.; HOGAN, T. P.; ROCCI-LANE, M.; BRAZIS, P.; IRELAND, J. R.; KANNEWURF, C. R.; BASTEA, M.; UHER, C.; KANATZIDIS*, M. G.; J. Am. Chem. Soc. 126 (2004) 20, 6414-6428; Dep. Chem., Mich. State Univ., East Lansing, MI 48824, USA; Eng.) -Schramke 33-018 Te -6

Black single crystals of the two nonstoichiometric cerium coinage-metal oxysulfide compounds CeCu(x)OS and CeAg(x)OS (x approximately 0.8) have been prepared by the reactions of Ce2S3 and CuO or Ag2O at 1223 or 1173 K, respectively. A black powder sample of CeAgOS has been prepared by the stoichiometric reaction of Ce2S3, CeO2, Ag2S, and Ag at 1073 K. These isostructural materials crystallize in the ZrSiCuAs structure type with two formula units in the tetragonal space group P4/nmm. Refined crystal structure results and chemical analyses provide evidence that the previously known anomalously small unit-cell volume of LnCuOS for Ln = Ce (Ln = rare-earth metal) is the result of Cu vacancies and the concomitant presence of both Ce3+ and Ce4+. Both CeCu(0.8)OS and CeAgOS are paramagnetic with mu(eff) values of 2.13(6) and 2.10(1) mu(B), respectively. CeCu(0.8)OS is a p-type semiconductor with a thermal activation energy Ea = 0.22 eV, sigma(electrical) = 9.8(1) 10(-3) S/cm at 298 K, and an optical band gap Eg < 0.73 eV. CeAgOS has conductivity sigma(conductivity) = 0.16(4) S/cm and an optical band gap Eg = 0.71 eV at 298 K. Theoretical calculations with an on-site Coulomb repulsion parameter indicate that the Ce 4f states are fully spin-polarized and are not localized in CeCuOS, CeCu(0.75)OS, or CeAgOS. Calculated band gaps for CeCu(0.75)OS and CeAgOS are 0.6 and 0.8 eV, respectively.

Liquid Ga was used as a solvent to explore the phase formation between rare-earth metals (REs), Ni, and a tetrelide (Tt = Si, Ge). The reactions were performed in excess liquid Ga at 850 °C. Two new phases of general formulas RE0.67Ni2Ga5 - x Tt x and RE0.67Ni2Ga6 - x Tt x were found and structurally characterized. The Co analogues of the latter RE0.67Co2Ga6 - x Ge x (RE = Y, Gd) were also prepared. Single-crystal X-ray data:  The first group of compounds RE0.67Ni2Ga5 - x Tt x crystallizes in the hexagonal space group P63/mmc with a structure related to the RE2 - x Pt4Ga8+ y type (Sm0.53Ni2Ga5 - x Ge x , a = 4.1748(7) Å, c = 16.007(4) Å, V = 241.61(8) Å3, Z = 2; Y0.59Ni2Ga5 - x Ge x , a = 4.1344(11) Å, c = 15.887(6) Å, V = 235.18(12) Å3, Z = 2; Tb0.67Ni2Ga5 - x Si x , a = 4.1415(11) Å, c = 15.843(6) Å, V = 235.33(12) Å3, Z = 2; Ho0.67Ni2Ga5 - x Ge x , a = 4.1491(4) Å, c = 15.877(2) Å, V = 236.71(5) Å3, Z = 2). The second group RE0.67Ni2Ga6 - x Tt x crystallizes in P6̄m2 (Gd0.67Ni2Ga6 - x Ge x , a = 4.1856(10) Å, c = 9.167(3) Å, V = 139.08(7) Å3, Z = 1; Sm0.67Ni2Ga6 - x Si x , a = 4.1976(8) Å, c = 9.159(3) Å, V = 139.76(5) Å3, Z = 1) in a structure related to the ErNi3Al9 structure type with disorder in the RE−Ga plane. Dy0.67Ni2Ga6 - x Ge x crystallizes in space group P3̄1c (a = 7.2536(8) Å, c = 18.308(3) Å, V = 834.21(2) Å3, Z = 6) with partial disorder in the RE−Ga plane. The structures of these two groups of compounds are related to each other and contain similar building motifs, namely Ga n [NiGa2 - x /2Ge x /2]2 slabs and RE0.67Ga monatomic layers which alternate along the c-direction, forming a 3D structure. The parameter x and the position of the tetrelide in the structure were determined by single-crystal neutron diffraction. Complete or partial disorder of the RE and Ga atoms is observed in the RE−Ga plane. The origin of the disorder lies in the extensive and random stacking faults of ordered RE−Ga planes, which apparently slide easily in the ab plane and create an averaged disordered picture. Electrical conductivity and thermopower measurements indicate that these compounds are metallic conductors. The magnetic measurements show antiferromagnetic ordering at ∼3−4 K and Curie−Weiss behavior at higher temperatures with the values of μeff close to those of RE3+ free ions. Strong 2-fold crystal field anisotropy is observed for the heavy RE analogues. The anisotropy constants K 2 para calculated from the Weiss constant anisotropy for heavy RE analogues are reported.

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