Thermal Analysis of LiGaO2 and NaGaO2

The high-temperature thermal properties of the ternary oxides LiGaO₂ and NaGaO₂ are studied by simultaneous differential thermal analysis and thermogravimetry between room temperature and about 1700 °C. For the melting temperature of LiGaO₂ a value of 1595 ± 10 °C is determined. NaGaO₂ undergoes a solid state phase transition at 1280 ± 10 °C and melts at 1395 ± 10 °C.     

Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (II). Interatomic force constants

The frequencies of the wurtzite-like modes due to Li–O and Ga–O bond vibrations in LiGaO₂ and of the rocksalt-like mode due to Li–O bond vibrations in LiInO₂ are determined from the infrared reflectivity spectra of the compounds. The force constants for the Li–O and Ga–O bonds in LiGaO₂ follow the same trends as those found for the A^IB^IIIC₂^VI chalcogenides with tetrahedral cordination. The results for LiInO₂ are compared with measurements on the octahedrally coordinated modification of LiAlO₂.     

Effect of the oxygen pressure during annealing on Tc and lattice parameter c of Bi-2212 single crystals

The influence of oxygen partial pressure (p_o2 = 10⁻⁴–1.5 · 10² atm) during annealing on the T_c and lattice parameter c of Bi-2212 single crystals has been investigated. Antibate correlation between non-monotonous alteration of the c parameter and T_c with the increase in oxygen content has been revealed.     

Growth,electrical and optical behaviour of nanocrystalline Ag2Cu2O3 films produced by RF magnetron sputtering

Thin films of Ag₂Cu₂O₃ were formed on glass substrates by RF magnetron sputtering technique under different oxygen partial pressures in the range 5 × 10^‐3 – 8 × 10^‐2 Pa using mosaic target of Ag₇₀Cu₃₀. The influence of oxygen partial pressure on the core level binding energies, crystallographic structure, and electrical and optical properties of the deposited films was studied. The atomic ratio of copper to silver in the films was 0.302. The oxygen content was in correlation with the oxygen partial pressure maintained during the growth of the films. The films formed at oxygen partial pressures < 2 × 10^‐2 Pa was mixed phase of Ag₂Cu₂O₃ and Ag. The films deposited at 2 × 10^‐2 Pa were single phase of Ag₂Cu₂O₃. The crystallite size of the films formed at 2 × 10^‐2 Pa was 12 nm, while those films annealed at 473 K was 16 nm. The nanocrystalline Ag₂Cu₂O₃ films formed at oxygen partial pressure of 2 × 10^‐2 Pa showed electrical resistivity of 8.2 Ωcm and optical band gap of 1.95 eV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the crystal structure type of 2 CsCl · CoCl2 · 2 H2O

The following three-component systems have been studied: CsCl MnCl₂ H₂O at 25 °C; 2 CsCl · CuCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 10 °C and 2 CsCl · MnCl₂ · 2 H₂O—2 CsCl · CoCl₂ H₂O at 25 °C and 10 °C. It was established that Co²⁺-ions do not substitute isodimorphously the Cu²⁺-ions in the tetragonal salt 2 CsCl · CuCl₂ · 2 H₂O, whereas in the case of the triclinic salt 2 CsCl · MnCl₂ · 2 H₂O they can substitute isodimorphously the Mn²⁺-ions. The theoretical considerations supported by the results obtained allow to predict the existence of the double salt 2 CsCl · CoCl₂ · 2 H₂O as well as the type of its crystal structure — triclinic, space group P1 .     

Growth kinetics,structure and surface morphology of AlN/α-Al2O3 epitaxial layers

The gas-phase epitaxy of AlN on saphire substrates in the system Al HCl NH₃–Ar was investigated. The uniformity and structural perfection of the layers were shown to be determined by gas dynamics in the growth zone. The growth rate of AlN-layer is proportional to AlCl concentration in the growth zone and does not depend on NH₃ partial pressure. This is in accordance with the law of diffusional stoichiometry. The morphology of AlN-layers was shown to be dependent on the growth rate and the substrate orientation. Smooth mirror-like layers were prepared on the sapphire planes (0001) and (1120) at low growth rates. X-ray microanalysis showed the oxygen impurity content at the level 1 — 5 · 10²¹ cm⁻³. Other impurities were not available.     

Bond Ionicities and Structural Trends in Some LiBIIIC Compounds

The individual and average bond ionicities of LiAlO₂, LiGaO₂, LiInS₂, LiInSe₂ and LiInTe₂ are evaluated from spectroscopic data. It is found that in these compounds the Li C^VI bond is essentially ionic in nature. It is shown that the structural properties of the compounds can be understood in terms of the average bond parameters.     

The solubility and activity determination of NiO in the SiO2-NiO-FeO system

A structural model for the liquid phase of silicate systems was used to obtain the SiO₂-NiO-FeO phase diagram and the NiO activities at 1573 and 1673 K. The NiO activities were determined experimentally by equilibrating a pure nickel crucible with an iron-silicate slag and CO-CO₂ gas mixture to produce pO₂ = 10⁻⁶ and 10⁻¹⁰ atm. The NiO activities obtained by the structural model are in good agreement with those obtained experimentally for strongly reduction conditions (10⁻¹⁰ atm), due to the structural model consider only the iron in the divalent state. The Fe³⁺/Fe²⁺ ratio and the nickel oxide solubility were increased when the oxygen partial pressure and the temperature were increased.     

Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (I) experimental results

Infrared reflectivity spectra of LiGaO₂ and LiInO₂ samples pressed from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. The optical mode frequencies found for LiGaO₂ agree with measurements on single crystals. In LiInO₂ four vibrational modes are found. Comparing the results for LiGaO₂ some conclusions are made with regard to the Li O bond related vibrational modes.     

First-principles calculations of the V3+ absorption spectra in LiAlO2 and LiGaO2

The systematic first-principles analysis of the energy level schemes and ground state absorption (GSA) of the V³⁺ ion in two oxide crystals LiAlO₂ and LiGaO₂ was performed. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron method (DV-ME) [K. Ogasawara, T. Iwata, Y. Koyama, T. Ishii, I. Tanaka, H. Adachi, Phys. Rev. B 64 (2001) 115413] was used in the calculations. The method is based on the numerical solution of the Dirac equation; no phenomenological parameters are used in the calculations. As a result, complete energy level schemes of V³⁺ ion and its absorption spectra in both crystals were calculated, assigned and compared with experimental data.     

The effect of oxygen partial pressure on physical properties of nano‐crystalline silver oxide thin films deposited by RF magnetron sputtering

Nano‐crystalline silver oxide films were deposited on glass and silicon substrates held at room temperature by RF magnetron sputtering of silver target under different oxygen partial pressures. The influence of oxygen partial pressure on the structural, morphological, electrical and optical properties of deposited films was investigated. Varying oxygen partial pressure during the sputter deposition leads to changes of mixed phase of Ag₂O and Ag to a single phase of Ag₂O and to AgO. The X‐ray diffraction and X‐ray photoelectron spectroscopy results showed the formation of single phase Ag₂O with cubic structure at oxygen partial pressures of 2x10^‐2 Pa while the films deposited at higher oxygen partial pressure of 9x10^‐2 Pa showed the formation of single phase of AgO with monoclinic structure. Raman spectroscopic studies on the single phase Ag₂O showed the stretching vibration of Ag‐O bonds. Single‐phase Ag₂O films obtained at oxygen partial pressure of 2x10^‐2 Pa were nano‐crystalline with crystallite size of 20 nm and possessed an electrical resistivity of 5.2x10^‐3 Ωcm and optical band gap of 2.05 eV. The films deposited at higher oxygen partial pressure of 9x10^‐2 Pa were of AgO with electrical resistivity of 1.8x10^‐2 Ωcm and optical band gap of 2.13 eV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,etching morphology and spectra of LiAlO2 crystal

γ‐LiAlO₂ single crystal was successfully grown by Czochralski method. The crystal quality was characterized by X‐ray rocking curve and chemical etching. The effects of air‐annealing and vapor transport equilibration (VTE) on the crystal quality, etch pits and absorption spectra of LiAlO₂ were also investigated in detail. The results show that the as‐grown crystal has very high quality with the full width at half maximum (FWHM) of 17.7‐22.6 arcsec. Dislocation density in the middle part of the crystal is as low as about 3.0×10³ cm^–2. The VTE‐treated slice has larger FWHM value, etch pits density and absorption coefficient as compared with those of untreated and air‐annealed slices, which indicates that the crystal quality became inferior after VTE treatment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Room temperature epitaxial growth of (001) CeO2 on (001) LaAlO3 by pulsed laser deposition

The room temperature epitaxial growth of CeO₂ on lattice matched (001) LaAlO₃ substrates by using pulsed laser deposition (PLD) method under various oxygen partial pressure (Po₂) is demonstrated. X‐ray diffraction analysis with 2‐Theta/rocking curve/Phi‐scan, cross‐sectional transmission electron microscopy with selected‐area diffractions are used to characterize structural of grown films. The epitaxial (001) CeO₂ can be achieved at room temperature under Po₂ less than 2 × 10⁻³ Torr. The best quality of grown film is obtained under Po₂ = 2 × 10⁻⁵ Torr and degraded under Po₂ = 2 × 10⁻⁶ Torr due to oxygen deficiency in structure. The epitaxial relationship between CeO₂ and LAO is confirmed to be (001)CeO₂ //(001)LAO, [100]_CeO2//[110]_LAO and [010]_CeO2//[10]_LAO. No obvious reduction reaction occurred, from Ce⁺⁴ turned into Ce⁺³ states, as reducing oxygen partial pressure during growth by PLD.     

Structural and Electrical Characterization of Ag3Ga5Te9 and Ag3In5Se9 Crystals

X-ray powder diffraction studies revealed that Ag₃Ga₅Te₉ and Ag₃In₅Se₉ crystallize in orthorhombic and tetragonal systems, respectively. The temperature dependent conductivity and Hall effect measurements have been carried out between 65—480 K. Ag₃Ga₅Te₉ exhibits p-type conduction with a room temperature conductivity of 4.3 × 10^—4 (Ω · cm)^—1 and mobility less than 1 cm²/V · s. Ag₃In₅Se₉ was identified to be n-type with room temperature conductivity 7.2 × 10^—5 (Ω · cm)^—1 and mobility 20 cm²/V · s. From temperature dependence of the conductivity three different impurity ionization energies were obtained for both compounds. The anomalous behavior observed in the temperature dependence of mobility was attributed to the different features of the microstructure.     

Spectroscopy,oxidation-reduction behaviour and DC conductivity of a vanadium-containing barium aluminoborate glass

The vanadium(IV)-vanadium(V) equilibrium in a 37.5BaO, 5.0Al₂O₃, 57.5B₂O3 mol% + X mol% V₂O₅ (where X = 0.25?32.5) glass system has been studied as functions of temperature, partial pressure of oxygen and total vanadium concentration of the melt. The vanadium(V)/vanadium(IV) ratio in the melt increased with increasing partial pressure of oxygen, lowering temperature of melting, and with increasing total vanadium content of the melt. With X ? 10, the vanadium(V)/vanadium(IV) ratio became almost independent of the total vanadium content of the melt.With this knowledge of oxidation-reduction behaviour, a series of glasses containing 2.8?32.5 mol% V₂O₅ (at about 4 mol% intervals) and having a constant vanadium(IV)/vanadium(V) ratio (0.17) were prepared. Density, electronic absorption spectrum (both d-d and charge transfer transitions), and ESR of these glasses were measured. Optical and ESR spectra of these glasses indicated the vanadium(IV) to be present as vanadyl ion, VO²⁺; g| decreased monotonically with increasing vanadium content of these glasses, whereas gβ remained unchanged. The charge transfer transition energy due to vanadium(V) decreased, and the extinction coefficient increased by orders of magnitude with increasing vanadium content of the glass; the most striking changes occurred at X ≈ 10 mol%. DC conductivity of these glasses was measured at different temperatures; a plot of log (?/T) versus 1/T produced straight lines. The slope of these lines remained almost constant (39 ± 1 kcal/mol) for the glasses containing up to about 10 mol% V₂O₅; with further increase of V₂O₅ the slope decreased sharply.It has been concluded that the abrupt changes in properties like partial molar volume of V₂O₅, charge transfer spectrum of vanadium(V), activation energy of polaron hopping — all of which occurred around X ≈ 10 mol% — is due to a major change in the nature of vanadate groups rather than vanadium(IV) in these glasses.     

Amorphous tungsten-doped In2O3 transparent conductive films deposited at room temperature from metallic target

Amorphous tungsten-doped In₂O₃ (IWO) films were deposited from a metallic target by dc magnetron sputtering at room temperature. Both oxygen partial pressure and sputtering power have significant effects on the electrical and optical properties of the films. The as-deposited IWO films with the optimum resistivity of 5.8 × 10^?4 Ω·cm and the average optical transmittance of 92.3% from 400 to 700 nm were obtained at a W content of 1 wt%. The average transmittance in the near infrared region (700–2500 nm) is 84.6–92.8% for amorphous IWO prepared under varied oxygen partial pressure. The mobility of the IWO films reaches its highest value of 30.3 cm² V^?1 s^?1 with the carrier concentration of 1.6 × 10²⁰ cm^?3, confirming their potential application as transparent conductive oxide films in various flexible devices.     

Crystal and molecular structure of catena-μ-acetatomonobromodiamminecopper(II), C2H9BrCuN2O2

The crystal structure of catena-μ-acetatomonobromodiamminecopper([I]), C₂H₉BrCuN₂O₂, has been determined by three-dimensional Patterson and Fourier methods, and refined by least-squares procedures to R=4·7%. The orthorhombicPnma unit cell of dimensions a=9·01(1), b=7·60(1), c=10·38(1) Å contains 4 formula-entities. Two oxygen atoms from different acetate groups (Cu-O=2·001(6) and 1·995(5) Å) and two ammonia molecules (Cu-N=1·984(6) Å) coordinate to the copper atom in atrans square-planar arrangement. This is extended to square-pyramidal by a long contact with the bromine atom (Cu-Br=2·865(3) Å). One more long contact with the other oxygen atom of the carboxyl group (Cu-O(1ⁱ)=2·942(7) Å) realizes a distorted octahedral coordination. The acetate groups lie in mirror planes, and bridge the coordination polyhedra in zig-zag chains parallel to [100].     

Effect of calcination on the crystallinity of sputtered TiO2 thin films as studied by Raman scattering

Titanium dioxide films have been deposited using DC magnetron sputtering technique onto silicon substrates at an ambient temperature and at an oxygen partial pressure of 7 × 10 ^–5 mbar and sputtering pressure (Ar + O₂) of 1 × 10 ^–3 mbar. The deposited films were calcinated at 673 and 773 K. The composition of the films as analyzed using Auger Electron Spectroscopy (AES) revealed the stoichiometry with an O and Ti ratio of 2.08. The influence of post‐deposition calcination on the Raman scattering of the films was studied. The existence of Raman active modes A_1g, B_1g and E_g corresponding to the Raman shifts are reported in this paper. The improvement of crystallinity of the TiO₂ films as shown by the Raman scattering studies has also been reported. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetics of luminescence of CsI single crystals scavenged by Y3+

CsI single crystals were grown from the melt scavenged by Y³⁺ (YCl₃) addition in 6.7·10⁻⁴–6.7·10⁻³ mol·kg⁻¹ range. The addition of the scavenger amounts comparable with the total concentration of the oxygen‐containing admixtures in molten CsI results in complete destruction of the latter. Because of this, the intensity of the band with a maximum at 2.8 eV in radioluminescence spectra caused by the oxygen‐containing admixtures (anion vacancies) considerably decreases, and the fraction of the slow 2μs‐component corresponding to these admixtures becomes lower than 0.01 (0.007). The addition of larger quantities of YCl₃ leads to the appearance of a wide band with a maximum at 2.8 eV caused by cation vacancies, and the intensity of the slow 2μs‐component increases to 0.02. The maximum ratio of two faster components with the decay constants equal to 7 and 30 ns reaches 0.65:0.33 at Y³⁺ concentration in CsI melt equal to 6.7·10^‐3 mol·kg^‐1, the effective luminescence time of fastest components is ca 14 ns. The dependence of the ‘Fast/Total ratio’ on Y³⁺ concentration passes through its maximum (0.81) corresponding to the equivalence of Y³⁺ and O²⁻ concentrations in the growth CsI melt.     

Vibrational Properties of LiGaO2 (I). Experimental Results

Infrared reflectivity spectra of LiGaO₂ are measured at room temperature in the wave-number range from 200 to 4000 cm¹ for the polarization directions E ∥ a and E ∥ c. The parameters of 10 B₁ modes and 4 A₁ modes are determined by a dispersion analysis of the spectra. The results obtained are compared with previous Raman scattering measurements.