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Transport properties, namely electrical conductivity, Seebeck and Hall coefficients, and thermal conductivity, were measured from 80 to 560 K. The phase transition at about 410 K, representing the phase transition from α-Ag2Te to β-Ag2Te, influences the electrical transport properties. The temperature dependence of Hall coefficient passes through a maximum ∼200 K and has a negative sign. It is shown that these peculiarities are due to the presence of Ag2Te phase. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry studies of AgSbSe2 are conducted, and the spectra of the permittivity and optical constants in the energy range 0.07–6.5 eV are determined. To describe the experimental spectra, the Tauc–Lorentz, modified Forouhi–Bloomer, and Cody–Lorentz models are used. It is found that the Cody–Lorentz model more adequately describes the near-edge region of the spectra of optical constants. It is shown that the optical properties, the shape of the absorption edge, and the structure of the band gap are substantially influenced by the spatial structural disorder of AgSbSe2 crystals. From analysis of the experimental spectra by different methods, the band gap of AgSbSe2, Eg, is determined: Eg = 0.32 eV. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry studies of AgSbSe2 are conducted, and the spectra of the permittivity and optical constants in the energy range 0.07–6.5 eV are determined. To describe the experimental spectra, the Tauc–Lorentz, modified Forouhi–Bloomer, and Cody–Lorentz models are used. It is found that the Cody–Lorentz model more adequately describes the near-edge region of the spectra of optical constants. It is shown that the optical properties, the shape of the absorption edge, and the structure of the band gap are substantially influenced by the spatial structural disorder of AgSbSe2 crystals. From analysis of the experimental spectra by different methods, the band gap of AgSbSe2, Eg, is determined: Eg = 0.32 eV. [ABSTRACT FROM AUTHOR]

Temperature dependences of the Hall and Seebeck coefficients in Ag0.82Sb1.18Te2.18 and AgSbTe2 are studied in the temperature range 4.2–320 K. It is found that the Hall coefficient in Ag0.82Sb1.18Te2.18 does not depend on the magnetic field, while for AgSbTe2, a weak dependence on the magnetic field is observed. The effective mass of holes (m* = 0.61m0) in Ag0.82Sb1.18Te2.18 is determined. [ABSTRACT FROM AUTHOR]

Temperature dependences of the Hall and Seebeck coefficients in Ag0.82Sb1.18Te2.18 and AgSbTe2 are studied in the temperature range 4.2–320 K. It is found that the Hall coefficient in Ag0.82Sb1.18Te2.18 does not depend on the magnetic field, while for AgSbTe2, a weak dependence on the magnetic field is observed. The effective mass of holes (m* = 0.61m0) in Ag0.82Sb1.18Te2.18 is determined. [ABSTRACT FROM AUTHOR]

AgSbSe2 and (AgSbSe2)0.9(PbTe)0.1 have been characterized by X-ray diffraction, differential scanning calorimetry, and temperature-dependent electric conductivity and thermoelectric power measurements in the range 80–330 K. The results demonstrate that charge transport in both materials is due to hopping of charge carriers between localized states. We have evaluated the temperature range of hopping conduction and the Fermi level density of localized states in these materials. [ABSTRACT FROM AUTHOR]

AgSbSe2 and (AgSbSe2)0.9(PbTe)0.1 have been characterized by X-ray diffraction, differential scanning calorimetry, and temperature-dependent electric conductivity and thermoelectric power measurements in the range 80–330 K. The results demonstrate that charge transport in both materials is due to hopping of charge carriers between localized states. We have evaluated the temperature range of hopping conduction and the Fermi level density of localized states in these materials. [ABSTRACT FROM AUTHOR]

It was investigated that the influence of Ca substitution by Zn on the specific resistivity, thermal power, and excess conductivity of Bi2Sr2CaCu2OX, Bi2Sr2Ca0.8Zn0.2Cu2OX, and Bi2Sr2Ca0.4Zn0.6Cu2OX polycrystalline samples in the 70–300 K temperature interval. The fluctuation-induced conductivity is analyzed using the Aslamasov and Larkin and Lawrence and Doniach models. The microscopic parameters such as dimensional crossover temperature (Tcr), interlayer coupling strength (J), and zero temperature coherence length along c axis (ξ0) are estimated. [ABSTRACT FROM AUTHOR]

It was investigated that the influence of Ca substitution by Zn on the specific resistivity, thermal power, and excess conductivity of Bi2Sr2CaCu2OX, Bi2Sr2Ca0.8Zn0.2Cu2OX, and Bi2Sr2Ca0.4Zn0.6Cu2OX polycrystalline samples in the 70–300 K temperature interval. The fluctuation-induced conductivity is analyzed using the Aslamasov and Larkin and Lawrence and Doniach models. The microscopic parameters such as dimensional crossover temperature (Tcr), interlayer coupling strength (J), and zero temperature coherence length along c axis (ξ0) are estimated. [ABSTRACT FROM AUTHOR]

The temperature dependencies of the thermal conductivity of AgSbTe2 and Ag0.82Sb1.18Te2.18 were studied in the temperature range of 5–320 K. The obtained results are compared with quantitative calculations based on a theoretical model of generalized conductivity of heterogeneous systems. It was shown that a rather low value of thermal conductivity of AgSbTe2 and Ag0.82Sb1.18Te2.18 is associated with the disordering of the crystal structure, as well as phonon scattering by point defects and structural components. The presence of the second phase of Ag2Te leads to an increase in the thermal conductivity of AgSbTe2. [ABSTRACT FROM AUTHOR]

The temperature dependencies of the thermal conductivity of AgSbTe2 and Ag0.82Sb1.18Te2.18 were studied in the temperature range of 5–320 K. The obtained results are compared with quantitative calculations based on a theoretical model of generalized conductivity of heterogeneous systems. It was shown that a rather low value of thermal conductivity of AgSbTe2 and Ag0.82Sb1.18Te2.18 is associated with the disordering of the crystal structure, as well as phonon scattering by point defects and structural components. The presence of the second phase of Ag2Te leads to an increase in the thermal conductivity of AgSbTe2. [ABSTRACT FROM AUTHOR]

Long-lived minima are detected at Tmin1 = 275 K and Tmin2 = 252 K in the ρ(T) curve of polycrystalline CdBa2Cu3O7-δ, which has a superconducting transition at 86.8 K. It is shown that the excess conductivity Δσ(T) near Tmin obeys the classical Aslamazov-Larkin fluctuation theory. This suggests that fluctuation Cooper pairs may develop in CdBa2Cu3O7-δ at T > Tc. The experimental data are used to calculate the coherence length ξc(0), the 2D-3D crossover temperature T0, and the interplanar pairing constants. The magnitude and temperature dependence of the pseudogap for a sample without the minima are found to be typical of cuprate HTSC materials. [ABSTRACT FROM AUTHOR]

A new superconducting ceramic material CdBa2Cu3O7-δ is obtained. It is found that the superconducting transition (at 86 K) is retained when yttrium is fully replaced by cadmium in the Y-Ba-Cu-O system. X-ray diffraction studies show that the crystalline structure is unchanged and the identified peaks coincide when Y is replaced by Cd in YBa2Cu3O7-δ. Besides a stable superconducting transition, a phase transition near 275 K was seen in the temperature dependence of the specific resistivity which shifted toward lower temperatures (252 K) and then disappeared completely over repeated measurement cycles. The thermal conductivity k of YBa2Cu3O7-δ and CdBa2Cu3O7-δ was found to vary little with temperature up to the superconducting transition. Substituting Cd for Y in the initial HTSC material led to a substantial increase in the lattice thermal conductivity. Measurements of the thermal emf showed that it is positive in YBa2Cu3O7-δ and negative in CdBa2Cu3O7-δ. [ABSTRACT FROM AUTHOR]

A study of the influence of magnetic field on the thermal conductivity of Bi2Sr2CaCu2Ox is made. It is found that the thermal conductivity increases under the influence of magnetic field because the electronic part of the thermal conductivity increases on account of breaking of the Cooper pairs and a decrease of the phonon-vortex scattering. [ABSTRACT FROM AUTHOR]

The composition of synthesized ceramic samples is investigated by x-ray phase analysis, and it is established that they are high-Tc superconducting Bi2Sr2ZnCu2Ox. It is found that the crystal structure is preserved. To investigate how the superconductivity of Bi–Sr–Ca–Cu–O is influenced by the substitution of calcium by zinc, measurements of the temperature dependence of the resistivity, thermal conductivity, and thermopower (Siebeck coefficient) are carried out. It is found that the substituted compound Bi2Sr2ZnCu2Ox retains its superconducting properties (T0=82 K). It is shown that substitution of Ca by Zn leads to an increase of the thermal conductivity. While the thermopower of Bi2Sr2CaCu2Ox shows p-type conductivity in the whole range of temperatures investigated, in Bi2Sr2ZnCu2Ox the type of the conductivity is changed to n-type. [ABSTRACT FROM AUTHOR]

A modified analytical Aslamazov-Larkin formula for the temperature dependence of the fluctuation conductivity near the critical temperature Tc is obtained for two-band superconducting compounds on the basis of linearized equations of the two-band Ginzburg-Landau theory. The results are compared to experimental data for the high- Tc superconductor compound Bi2Sr2CaCu2O8 + δ. [ABSTRACT FROM AUTHOR]

Experimental investigations of the Maggi-Righi-Leduc, Righi-Leduc, and Nernst-Ettingshausen thermomagnetic effects have been performed on three samples of the solid solution Bi[sub 0.88]Sb[sub 0.12], doped with tellurium from 0.01 to 0.2 at.%, in the temperature interval 20-230 K. The quantity L(T) is calculated from the experimental values of κ[sub e] and the thermomagnetic effects. It is found that in the interval 40-220 K L[sub exp] is less than its Sommerfeld value L[sub 0]. Comparing L (T) with the existing theory showed that the low value of L is due to inelastic electron-electron interaction. [ABSTRACT FROM AUTHOR]