Monoclinic Β-phase Research Articles

Effects of substrate temperature on copper(II) phthalocyanine thin films

We report the crystal and band gap structures of copper(II) phthalocyanine (Cu–Pc) thin films depending on the substrate heating conditions and temperatures. The phase changes of the two α- and β-phases of Cu–Pc thin films due to different heating conditions were observed by using X-ray diffractions and electronic absorption spectra. As the temperatures increased from room temperature to 300°C, the energy gap was changed from 1.8052 to 1.7844eV and the crystal structure of Cu–Pc thin films was transformed from orthorhombic α-phase to monoclinic β-phase. The orientation of grains depended on the heat-treatment conditions and the temperatures of the substrate during film deposition. The transport properties of Cu–Pc thin films with different grain orientations were studied.

Structural Investigation of Copper Phthalocyanine Thin Films Using X-Ray Diffraction, Raman Scattering and Optical Absorption Measurements

Structural properties of copper phthalocyanine (CuPc) powder and its thin films coated on glass plate are investigated using X-ray diffraction, Raman scattering and optical absorption techniques. These experiments are carried out at room temperature on CuPc powder and as-coated, 320 °C and 520 °C annealed, CuPc thin films. From the X-ray diffraction (XRD), we find that the CuPc powder exists in monoclinic phase, as-coated film is in orthorhombic α-phase and the film annealed at 320 °C exists in monoclinic β-phase with different lattice parameters as compared to those of the powder phase. The XRD peaks in 520 °C annealed film do not show the presence of CuPc but indicate the presence of copper oxide (CuO) nanoclusters of approximately 15 nm size. The optical Raman phonon frequencies of CuPc powder, as-coated and 320 °C annealed CuPc films show a slight shift in the intramolecular high frequency modes. Whereas, their low frequency Raman spectra from intermolecular modes are characteristically different indicating different phases. The different characteristic behavior of the optical absorption spectra of the as-coated and 320 °C annealed CuPc films corroborate the structural changes in the annealed film.

Ionic conductivity of Bi 3BaO 5.5 and Bi 3 − xM xBaO 5.5 − [formula omitted]( M = Pb, Cd) solid solutions

The cubic γ-Bi 3BaO 5.5 shows about half an order of magnitude higher ionic conductivity than that of the structurally distorted monoclinic β-phase. Solid solutions of the monoclinic isomorph Bi 3 − x M xBaO 5.5 − x 2 ( M = Pb, Cd) have been prepared by solid state reactions. The increase of ionic conductivity in these substituted phases is ascribed to the combined effect of decreasing activation energy and increasing preexponential factor.

Structural variants in the low-temperature β phase of stoichiometric cuprous selenide

Symmetry lowering from T 2 d(F 43m) to C 3 s ( Cm) at α → β first-order phase transition of the superionic conductor Cu 2Se is described by two nonequivalent wave vectors: k R = 2π a c ( 111 222 ) and k m= 2π a c ( 11 33 0) Four orientation variants of the rhombohedrally deformed cage sublattice are equally probable equilibrium structures which correspond to four rays in the star of k R. Such twinning was observed using a microfurnace built for the Weissenberg goniometer. Three monoclinic β-phase structure variants displaying together pseudorhombohedral symmetry can couple to each body cube diagonal as a cage distortion direction, giving a total of 12—the number of rays in the star of k m .

ChemInform Abstract: A High Pressure Phase of Strontium Orthogermanate.

AbstractIt is demonstrated that orthorhombic α'‐Sr2GeO4 can be completely transformed to the monoclinic β‐phase by exposure to pressures > 5 kbar at room temp., whereas the transformation predicted to occur at ‐45 °C (based on DTA results) is largely incomplete.

The crystal structure of α-1,2,4,5-tetrachlorobenzene based on spectroscopic evidence and packing and lattice frequency calculations

The crystal structure of α-l,2,4,5-tetrachlorobenzene has been investigated by spectroscopic methods and packing calculations. With the existing unit-cell parameters, the crystal has been found to belong to space group P{\bar 1} with two unrelated molecules located at (0,0,0) and (1/2, 1/2, 0). Atomic positions are given. The structure is closely related to that of the monoclinic βphase. Calculated lattice vibration frequencies are in good agreement with experiment.

Investigations on cesium urantes—III: Crystal structures of Cs 2U 4O 12

The crystal structures of three Cs 2U 4O 12 phases have been investigated by X-ray diffraction methods. The positions of the uranium and cesium atoms of the rhombohedral α-phase were obtained from single crystal X-ray analysis. The positions of the uranium and cesium atoms in the monoclinic β-phase and the cubic γ-phase could be obtained from X-ray powder analysis. Furthermore the oxygen atoms in the γ-phase could be located. The structures of Cs 2U 4O 12 are closely related to the crystal structure of UO 2.