Electrical conduction and thermal properties of Bi-doped Pr0·7Sr0·3MnO3 manganite

Electrical and thermal properties of Bi-doped Pr _0·7 Sr _0·3 MnO ₃ (PSMO) compounds are reported here. It is observed that Bi-doped PSMO compounds follow variable range conduction mechanism. Specific heat, thermal conductivity and thermo-power measurements show that larger Bi-ion, in place of smaller Pr ion, enhances their transition temperatures (T _MI, T _C, T _CP). Thermo-power measurements further strengthen our conclusion for the presence of magnetic polaron, generated due to hybridization of Bi ³⁺ –6s ² and O ^2? –2p orbital and polaronic conduction mechanism.     

Synthesis and characterization of a new solution-processable star-shaped small molecule based on 5,6-bis(n-octyloxy)-2,1,3-benzoselenadiazole for organic solar cells

A new star-shaped small molecule (M1) with triphenylamine as electron donor (D) unit and 4,7-dithienyl-5,6-bis(n-octyloxy)[2,1,3]benzoselenadiazole as electron acceptor (A) unit was designed and synthesized. The relationship between the structure and properties was well investigated. M1 shows excellent solubility in common organic solvents, broad absorption (300–650 nm), good optical band gap (E _g) (1.96 eV), and proper energy level. Meanwhile, we also investigated the performance of the organic solar cells (OSCs) based on M1 and PC ₆₁ BM or PC ₇₁ BM with different weight ratios, under the illumination of AM 1.5G, 100 mW/cm². The OSCs based on the blend of M1 and PC ₇₁ BM (1:2, w/w) exhibited the best device performance with a power conversion efficiency of 1.54 %, an open-circuit voltage of 0.91 V, a short-circuit current density of 4.54 mA/cm², and a fill factor of 37.2 %.     

Study of the law of corresponding states of viscous properties of classical liquids

The law of corresponding states is studied for the coefficients of shear η* _S and volume η* _V viscosities of classical liquids (Ar, Kr, Xe, O₂, N₂, CH₄); the analytical expressions are derived on the basis of kinetic equations for one- and two-particle distribution functions. The reduced iso-frequency coefficients Φ(|r|) and g(|r|) for liquid Ar, Kr, Xe, O₂, N₂, and CH₄ are numerically calculated in a wide range of variations at the reduced temperatures T* and densities ρ*, which satisfy the law of corresponding states, at a definite choice of the intermolecular interaction potential η _S * and radial distribution function η _V *.     

Dispersion-Induced Splitting of the Collective Mode Spectrum in Axial and Planar Phases of Superfluid 3He

The whole collective mode spectrum in axial and planar phases of superfluid ³He with dispersion corrections is calculated for the first time. In axial A-phase the degeneracy of clapping modes depends on the direction of the collective mode momentum k with respect to the vector l (mutual orbital moment of Cooper pairs), namely: the mode degeneracy remains the same as in case of zero momentum k for k‖l only. For any other directions there is a threefold splitting of these modes, which reaches maximum for k ⊥ l. In planar 2D-phase, which exists in the magnetic field (at H>H _C ) we find that for clapping modes the degeneracy depends on the direction of the collective mode momentum k with respect to the external magnetic field H, namely: the mode degeneracy remains the same as in case of zero momentum k for k‖H only. For any other directions different from this one (for example, for k ⊥ H) there is twofold splitting of these modes. The obtained results imply that new interesting features can be observed in ultrasound experiments in axial and planar phases: the change of the number of peaks in ultrasound absorption into clapping mode. One peak, observed for these modes by Ling et al. (J. Low Temp. Phys. 78:187, 1990), will split into two peaks in a planar phase and into three peaks in an axial phase under the change of ultrasound direction with respect to the external magnetic field H in a planar phase and with respect to the vector l in an axial phase. In planar phase, some Goldstone modes in the magnetic field become massive (quasi-Goldstone) and have a similar twofold splitting under the change of ultrasound direction with respect to the external magnetic field H. The obtained results as well will be useful under interpretation of the ultrasound experiments in axial and planar phases of superfluid ³He.     

Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO ₂ /Al ₂ O₃ membrane. α-Al ₂ O ₃ substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO₂ and diamond-like carbon (DLC) thin film were used. SiO ₂ and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO ₂ /Al ₂ O ₃ membrane were observed by FESEM. The phases of DLC and SiO ₂ thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO ₂ /Al ₂ O ₃ were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 μm-thick SiO₂ and 2 μm-thick DLC thin film annealed at 200 °C was ～18 ccm at 1018 mb back pressure.     

A new crystal structure for (BEDT-TTF)2SbF6 and some of its physical properties

A new crystal structure forbis (ethylenedithio)tetrathiafulvalene [(BEDT-TTF) ₂ SbF₆] was determined by single crystal X-ray diffraction. The crystal structure was refined in theP - 1 space group at room temperature. Crystal data for new structure are as follows: triclinic, a = 8.670 (2) Å,b = 8 664 (2) Å,c = 16.842 (5) Å,α = 89°.29 (2),β = 90°.71 (3),γ = 92°.67 (1),V = 1263.64 Å ³,Z = 2,D _x = 2.136 g cm ^-3, (Mo-Kα),λ = 0.7107 Å,R = 0.057 for a total of 5517 independent reflections. The donors form a trimerized column, and the band structure calculated by the tightbinding approximation shows band insulator properties. The temperature dependent of the d.c. resistivity shows a semiconducting behaviour with room temperature resistivity along the c-axis; ρ ₂₉₀ K = 5.6 ohm cm.     

Abnormal Behavior of the Angular Dependence of Resistivity in?YBCO?Thin Films

Careful investigation of the angular dependence of resistivity ??(??) (?? is the angle between the magnetic field and the ab-planes) as a function of the temperature within the superconducting transition in an applied magnetic field B up to 1 T for a series of YBa₂Cu₃O_7??? (YBCO) thin films revealed a large variation in the shape and width of the minimum displayed in the vicinity of ??=0??, from a flat to a very sharp behavior. The series of films studied included both optimally doped and underdoped samples of different T _c , critical current density?J _c , film thickness, and preparation techniques. ??(??) measured for B close to ??=0?? (B parallel to ab-planes) for both B??J and B??J (J is the applied current density) showed two classes of samples; class of samples where ??(??) is independent of the direction of B relative to J and the other class where ??(??) depends on the orientation B relative to?J. This unusual unique behavior motivated us to investigate its origin by looking at the scaling of ??(??) as a function of the reduced field. Scaling of ??(??)) with the reduced field B(?? ^?2cos?² ??+sin?²)^1/2 allowed a quantitative determination of the value of ?? (intrinsic anisotropy) which varies between 7 and 400, and is independent of film thickness and J _c . Analysis of the microstructure though XRD of the films studied showed that the anisotropy is related to microstrain of the films.     

Influence of Quenched Disorder on the Structural Properties and Spin-Wave Excitations in Ferromagnetic Metallic Manganites (La1−x Nd x )2/3(Ca1−y Sr y )1/3MnO3

The influence of quenched disorder on the structural properties and on low-temperature field-dependent magnetization, in terms of the spin-wave theory, of (La_1?x Nd _x )_2/3(Ca_1?y Sr _y )_1/3MnO₃ with J 1 (x=0,y=0); J 2 (x=0.05,y=0.04); J 3 (x=0.25,y=0.20); J 4 (x=0.3,y=0.24); J 5 (x=0.98,y=0.8) is investigated by characterizing a series of samples with the same A-site cational mean radius and the same average valence of the Mn ion but different A-site ionic radii variance. Our results demonstrate that moderate-small chemical disorder does not affect the crystallographic structure, but enhance the random local distortion of MnO₆ octhaedra. Magnetization measurements show that the Curie temperature (T _C ) decreases with disorder. The evolution of the saturation magnetization with the disorder cannot be deduced due to the possible contribution of the Nd spins to the total magnetic moment. The thermal evolution of magnetization in the ferromagnetic phase at low temperature varies as T ^3/2, in accordance with Bloch’s law. The spin wave stiffness constant D obtained from the Bloch constant is found to decrease with the increase of disorder. We found that for the range of the study disorder, the magnetic behavior corresponds to a conventional ferromagnet, where T _C should be proportional to D.     

Preparation of Zr50Al15−x Ni10Cu25Y x amorphous powders by mechanical alloying and thermodynamic calculation

Amorphous Zr ₅₀ Al _15?x Ni ₁₀ Cu ₂₅ Y _x powders were fabricated by mechanical alloying at a low rotation speed from commercial pure element powders. The beneficial effect of Al partially substituted by Y in Zr ₅₀ Al ₁₅ Ni ₁₀ Cu ₂₅ on glass-forming ability was investigated. The as-milled powders were characterized by X-ray diffraction and transmission electron microscopy. The results show that partial substitution of Al by Y can improve the glass-forming ability of Zr ₅₀ Al ₁₅ Ni ₁₀ Cu ₂₅ alloy. Thermodynamic calculation of equivalent free energy shows that Zr ₅₀ Al _13·8 Ni ₁₀ Cu ₂₅ Y _1·2 alloy has the highest glass-forming ability, which is in good agreement with the report of orthogonal experiments.     

Effects of thickness on electronic structure of titanium thin films

Effects of thickness on the electronic structure of e-beam evaporated thin titanium films were studied using near-edge X-ray absorption fine structure (NEXAFS) technique at titanium L _2,3 edge in total electron yield (TEY) mode and transmission yield mode. Thickness dependence of L _2,3 branching ratio (BR) of titanium was investigated and it was found that BR below 3·5 nm shows a strong dependence on film thickness. Mean electron escape depth (λ) in titanium, an important parameter for surface applications, was determined to be λ = 2·6 ± 0·1 nm using L _2,3 resonance intensity variation as a function of film thickness. The average L ₃ /L ₂ white line intensity ratio of titanium was obtained as 0·89 from the ratio of amplitudes of each L ₃ and L ₂ peaks and 0·66 from the integrated area under each L ₃ and L ₂ peaks. In addition, a theoretical calculation for pure titanium was presented for comparison with experimental data.     

Conductivity study of solid polyelectrolytes based on hydroiodide salt of poly(4-vinyl pyridine-co-butylmethacrylate), poly(4-vinyl pyridine-co-butylacrylate)

The chain flexibility of poly(4-vinylpyridine) was tried to increase by lowering its glass transition temperature ( T _g ) and by increasing its amorphous region by copolymerizing with butyl methacrylate and butylacrylate which act as internal plasticizer. The copolymers were prepared in five different feed molar ratios to optimize the required properties such as higher room temperature conductivity and better film-forming capacity. The conductivity and conduction behaviour of the copolymers, as well as their hydroiodide salts have been reported. There was about 10³–10⁴-fold increase in room temperature conductivity of these plasticized polyelectrolytes.     

Electrochemical copolymerization of N-methylpyrrole and 2,2′-bithitiophene; characterization,micro-capacitor study,and equivalent circuit model evaluation

N-methylpyrrole (N-MPy) and 2,2′-bithiophene (BTh) were electrocopolymerized in 0·2 M acetonitrile–sodium perchlorate solvent–electrolyte couple on a glassy carbon electrode (GCE) by cyclic voltammetry (CV). The resulting homopolymers and copolymers in different initial feed ratios of [N-MPy]₀/[BTh]₀ = 1/1, 1/2, 1/5 and 1/10 were characterized by CV, Fourier-transform infrared reflectance attenuated transmittance (FTIR–ATR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The capacitive behaviours of the modified electrodes were defined via Nyquist, Bode-magnitude, Bode-phase and admittance plots. The equivalent circuit model of R(C(R)(QR)(CR)) was performed to fit theoretical and experimental data. The highest low-frequency capacitance (C _LF) were obtained as C _LF = ～ 1·23 × 10 ^?4 mF cm ^?2 for P(N-MPy), C _LF = ～ 2·09 × 10 ^?4 mF cm^?2 for P(BTh) and C _LF = ～ 5·54 × 10 ^?4 mF cm^?2 for copolymer in the inital feed ratio of [N-MPy]₀/[BTh] ₀ = 1/2.

Kondo effect in superconducting diluteMoCo,MoFe, andMoMn alloys

The superconducting critical fieldsH _c and the critical temperaturesT _c have been measured down to 0.05 K in a series of dilute alloys ofMo Co,Mo Fe, andMo Mn. These systems haveT _K /T _c0 of 50, 0.3, and 15, respectively, whereT _K is the Kondo temperature of the alloy andT _c0 is the critical temperature of pure Mo. The critical fields atT=0 and the specific heat jump atT _c have been estimated from the observedH _c and compared with the theories of the magnetic impurity effect in superconductors. The behavior of these quantities and the density of states are found to depend strongly uponT _K /T _c0 in agreement with theory. From the results it is inferred that in the limit of largeT _K the superconducting properties of a Kondo alloy would tend to those of the Abrikosov-Gor'kov theory.     

Electronic Theory for the Magnetic Anisotropy in Sr2RuO4

Using a three-band Hubbard Hamiltonian we calculated within the random-phase-approximation the spin susceptibility, χ(q, ω), and NMR spin-lattice relaxation rate 1/T ₁, in the normal state of the triplet superconductor Sr₂RuO₄, and obtained quantitative agreement with experimental data. Most importantly, we found that because of spin–orbit coupling the out-of-plane component of the spin susceptibility χ ^zz (q, ω) becomes two times larger than the in-plane one at low temperatures. We analyze in particular the role of the xy-band in the magnetic anisotropy.     

Model verification of Lode’s test results and yield function of isotropic FCC polycrystal

Lode (Z Tech Phys 36:11–12, 1926) introduced what we now call the Lode stress parameter μ _S and the Lode plastic stretching or “strain-rate” parameter μ _D to verify the Lévy–Mises equation. If the Lévy–Mises equation is valid, the relation μ _D  = μ _S should hold. But Lode’s test results, as confirmed by Taylor and Quinney (Phil Trans R Soc Lond Ser A 230:323–362, 1931) and others, show systematic deviation from the equality μ _D  =  μ _S . Herein, for isotropic FCC polycrystals under triaxial loading, the Taylor–Bishop–Hill (TBH) theory is used to determine the Taylor factor ${\overline{M}(q)}$ , the yield deviatoric stress S, and the functional dependence of the plastic stretching ratio q(p) on the yield deviatoric stress ratio p. The function q(p) leads to a μ _D versus μ _S plot that manifests qualitatively the same deviation from the line μ _D  =  μ _S as the experimental results of Lode and others. We introduce a yield function with which we can reproduce all the macroscopic predictions we derived from the TBH theory, including the function q(p) and the relation between μ _D and μ _S . The yield function introduced is even in the yield deviatoric stress S and is a sixth degree polynomial in the components of S.     

Properties of polyethylene-propylene blends

High density polyethylene-isotactic polypropylene blends have been analysed using mechanical tensile tests at temperatures (T) ranging from25 up to 150° C and at crosshead speeds ranging from 0.01 to500 mm min^?1. The data have been tentatively interpreted in terms of cold and hot drawing mechanisms, depending on the values ofT andv. Such interpretation is quite different from that previously suggested in the literature. Using the results of this analysis it has been possible, by a suitable choice of the operating variablesT andv to yield ultradrawn blend fibres. Their mechanical properties, obtained at room temperature and at a cross-head speed of10 mm min^?1 have been analysed and discussed.     

Synthesis and characterization of tetraethylammonium tetrachlorocobaltate crystals

Single crystals of tetraethylammonium tetrachlorocobaltate were grown by solution method and characterized through single crystal X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetric studies (DSC) and infrared spectroscopic technique (IR). The crystals were bright, transparent and blue coloured. The unit cell parameters were found to bea =b = 90363 Å andc = 14.9879 Å and α = β = γ = 90°, showing tetragonal lattice from the XRD data. Thermogravimetric analysis showed a loss of weight at 683 K from which the decomposition reaction was formulated. Thermal anomalies were found for this crystal at temperatures 200 K, 220 K in the cooling cycle and at temperatures 200 K, 240 K in the heating cycle, respectively which showed that this crystal was associated with first order phase transition. All the vibrational frequencies corresponding to (TEA)⁺ ions and CoCl ₄ ^2? ions were assigned from the IR spectral data of this crystal.     

Novel D-π-A dye sensitizers of polymeric metal complexes with phenylethyl or carbazole derivatives as donors for dye-sensitized solar cells: synthesis,characterization, and photovoltaic application

Four novel polymeric metal complexes containing D-π-A type structures were synthesized, characterized and applied as dye sensitizers in dye-sensitized solar cells (DSSCs). The alkoxy benzene or carbazole (CZ) derivative acts as an electron donor (D), C=C acts as π-bridge (π) and the 8-hydroxyquinoline derivative complex acts as electron acceptor. Bipyridine derivative was ancillary ligand as well as providing anchoring group. FT-IR, gel permeation chromatography, thermogravimetric analyses, differential scanning calorimetry, UV–Vis absorption spectroscopy, Elemental analysis, cyclic voltammetry, J-V curves and input photon to converted current efficiency plots were introduced to investigate the four dyes. These dyes exhibit good thermal stability with 5 % weight loss at temperatures (T_d) of around 300 °C. For the DSSCs devices using dyes with CZ derivatives as electron D (P2, P4) exhibited higher power conversion efficiency (PCE) than that with alkoxy benzene (P1, P3). The DSSC based on P4 exhibited the highest PCE value of 2.42 % (J _sc  = 4.93 mA/cm², V _oc  = 0.73 V, FF = 67.2 %) under AM 1.5G solar irradiation. This indicates a new way to design dye sensitizers for DSSCs.     

High-field ESR on Light-Induced Transition of Spin Multiplicity in FeCo Complex

Cyanide-bridged Fe-Co complex [Fe(Tp)(CN)₃]₂Co(bpe)?5H₂O (1?5H₂O; Tp = hydro-tris(pyrazolyl)borate; bpe = 1,2-bis(4-pyridyl)ethane) shows temperature- and light- induced metal-to-metal charge transfer (MMCT) involving spin state changes between magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ (HS = high spin, LS = low spin) state and nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ state, while the dehydrated material 1 does not show any MMCT and holds $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state. We have investigated the magnetic properties of each spin state in 1 and 1?5H₂O by means of magnetization and ESR measurement under pulsed high magnetic field. At low temperature below T _N, in both 1 and 1?5H₂O, the saturation magnetization in the induced ferromagnetic phase is well explained by S and g values derived from the magnetic susceptibility study. In the ESR of 1, we observed characteristic modes corresponding to a spin excitation in the induced ferromagnetic phase where its temperature dependence shows an evolution of spin correlation in the $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state at low temperature. We further found that the similar ESR modes grow in the light-induced state of 1?5H₂O. The results strongly suggest that the light-induced magnetization in 1?5H₂O is driven by a light-induced MMCT, which involves transition of spin multiplicity from the nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ to the magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{\mathrm{II}}}\mathrm{HS}}$ pair.     

Synthesis and characterization of electrochromic poly(amide–imide)s bearing methoxy-substituted triphenylamine units

New poly(amide–imide)s (PAIs) 3a–d and 3′a–d with methoxy-substituted triphenylamine (TPA) units were prepared by the direct polycondensation from various imide ring-preformed dicarboxylic acids 2a–d with 4,4′-diamino-2″,4″-dimethoxytriphenylamine (1) and 4,4′-diamino-4″-methoxytriphenylamine (1′), respectively, using triphenyl phosphite and pyridine as condensing agents. For the comparative study, the referenced PAIs 3″a–d without methoxy substituents on the TPA unit were also prepared from 2a–d with 4,4′-diaminotriphenylamine (1″). All the polymers were readily soluble in many organic solvents and could be solution-cast into tough and flexible polymer films. The glass-transition temperatures (T_gs) of these PAIs ranged from 196 to 298 °C and the 10% weight-loss temperatures were in excess of 445 °C in nitrogen. Cyclic voltammograms of the PAI films cast onto the indium–tin oxide (ITO)-coated glass substrate exhibit one reversible oxidation redox couples at 0.73–0.89 V vs. Ag/AgCl in an electrolyte/acetonitrile solution. The polymer films revealed good electrochemical and electrochromic stability, with coloration change from a pale yellow neutral form to a green oxidized form. After over 100 redox cycles, the polymer films still exhibited good redox and electrochromic reversibility. The 3 and 3′ series PAIs exhibited enhanced redox-stability and electrochromic performance as compared to the parent 3″ analogs without methoxy substituents on the TPA unit.