Transport Properties Of Crystals Research Articles

Structural and electronic inhomogeneity of superconducting Nb-doped Bi2Se3

The crystal structure, electronic structure, and transport properties of crystals with the nominal composition ${\mathrm{Nb}}_{0.25}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ are investigated. X-ray diffraction reveals that the as-grown crystals display phase segregation and contain major contributions of BiSe and the superconducting misfit layer compound ${(\mathrm{Bi}\mathrm{Se})}_{1.1}\mathrm{Nb}{\mathrm{Se}}_{2}$. The inhomogeneous character of the samples is also reflected in the electronic structure and transport properties of different single crystals. Angle-resolved photoemission spectroscopy (ARPES) reveals an electronic structure that resembles poor-quality ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ with an ill-defined topological surface state. High-quality topological surface states are instead observed when using a highly focused beam size, i.e., nanoARPES. While the superconducting transition temperature is found to vary between 2.5 and 3.5 K, the majority of the bulk single crystals does not exhibit a zero-resistance state suggesting filamentary superconductivity in the materials. Susceptibility measurements of the system together with the temperature dependence of the coherence length extracted from the upper critical field are consistent with conventional BCS superconductivity of a type II superconductor.

Structure and transport properties of zirconia crystals co-doped by scandia, ceria and yttria

This work is a study of the effect of co-doping (ZrO2)0.9(Sc2O3)0.1 solid solution with yttria and/or ceria on the phase composition, local structure and transport properties of the crystals. The solid solution crystals were grown using directional melt crystallization in cold crucible. We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk, unlike yttria co-doping. Ceria co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals increases their conductivity, whereas the addition of 1 mol.% yttria tangibly reduces the conductivity. Equimolar co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals with ceria and yttria changes the conductivity but slightly. Optical spectroscopy of the local structure of the crystals identified different types of optical centers. We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals.

Effects of temperature and rare-earth doping on the transport properties of GaSe crystals

Transport properties (electrical conductivity and Hall coefficient) of pure (nominally undoped) and rare-earth-doped (up to 10−1 at % holmium, gadolinium, and dysprosium) gallium monoselenide crystals have been studied in the temperature range 77–600 K. The results demonstrate that, at low temperatures, the Hall coefficient of both the undoped and doped crystals is temperature-independent, whereas their dark conductivity and carrier mobility exhibit Arrhenius behavior. The undoped and rare-earth-doped crystals differ markedly in dark conductivity and carrier mobility. The chemical nature of the dopants has no effect on the transport properties of the crystals, which depend only on the doping level. The observed anomalies can be accounted for by the presence of random drift barriers in the empty energy bands of the gallium selenide crystals.

Gamma Ray Detection with Cd0.9Zn0.1Te Based Detectors Grown Using a Te Solvent Method

ABSTRACTCd0.9Zn0.1Te (CZT) single crystal has been grown using a tellurium solvent method. Two CZT crystals have been chosen from two different locations of the grown ingot. The two crystals were characterized using infrared transmission (IR) imaging and radiation detectors in planar geometry were fabricated on them. Current-voltage characteristics (I-V) revealed a resistivity of ∼8.6×1010 Ω−cm for detector A (6.9×6.9×4.8 mm3) and 6.7×1010 Ω−cm for detector B (11.5×11.7×2.6 mm3). IR imaging showed a lesser concentration of Te inclusions/precipitates in detector A. The transport properties viz., electron drift-mobility and electron mobility-lifetime product were measured using alpha spectroscopy in these detectors in a planar configuration. Detector A showed better charge transport properties compared to detector B. The superior transport properties of crystal A were reflected in the spectroscopic properties of the detectors. Gamma pulse height measurements using a 241Am isotope revealed an energy resolution of ∼5 % for detector A and ∼7 % for detector B. A digital spectrometer and a biparametric correction scheme was incorporated to recover the pulse height spectrum of high energy gamma rays (137Cs source) from the effect of poor hole movement.

Applications of impulsive stimulated scattering in the Earth and planetary sciences.

The elastic, thermodynamic, and transport properties of crystals and fluids at high temperature and pressure play a central role in the earth and planetary sciences as well as in a variety of technologies. These properties also constitute a principal experimental constraint on the description of intermolecular interactions at short distances. Aspects of "impulsive stimulated scattering," when adapted to measurements in the diamond-anvil high-pressure cell, provide an approach to the determination of a subset of equilibrium and dynamic properties at high density.

Heat transport properties of ferroelectrics and related materials

Abstract A review of experimental data on heat transport properties of crystals with ferroelectric and ferrodistortive phase transitions is presented. Special attention is paid to the temperature dependence of the thermal conductivity coefficient in order-disorder and displacive type phase transitions. An interpretation and a qualitative approach to the description of the heat transport coefficients anomalies are discussed.

Magnetic symmetry and transport properties in crystals

The number of non-vanishing independent tensor components in respect of the known transport properties for the magnetic variants of the crystallographic point groups are obtained by adopting a different procedure. This method fulfils the orthogonality conditions of group theory.

The effect of local-field correction on the transport properties of crystals

The question of local-field correction to the electrical transport is studied in more detail; namely, for the hopping limit and the band limit. In the hopping limit, if the hopping takes place between crystallographically equivalent sites, the short-range and Lorentz contributions to the dipolar potentials cancel in taking the intersite energy difference, and the electric field appearing in the hopping conductivity is just the macroscopic field. However if the hopping takes place between crystallographically inequivalent sites the short-range contributions to the dipolar potentials at the two sites do not cancel although the Lorentz contributions do. This leads to local-field-type corrections. The resulting corrections are found to be negligible at low fields but considerable at higher fields. Similar results are found for the Hall mobility of the small-polaron and AC impurity hopping conduction. In the band limit, it is shown that when the motion occurs in one band the net electric field appearing in the transport equation is just the macroscopic field unmodified by the local-field corrections.

The effect of temperature and pressure on the thermodynamic and transport properties of crystals in anharmonic approximation

The temperature and pressure dependence of the thermodynamic functions and transport coefficients of the three-dimensional face-centred cubic and body-centred cubic lattices are investigated on the basis of the dynamical theory of the anharmonic crystal. A comparison with experimental data are given for sodium and rubidium theoretically described by various potential functions.

Thermodynamic and Transport Properties of Crystals in Anharmonic Approximation

AbstractThe thermodynamic and transport properties of the three‐dimensional body‐centred cubic lattice are investigated on the basis of the dynamical theory of anharmonic crystals. It is shown that the anharmonic effects of lattice vibrations are not negligible in calculations concerning the high‐temperature region. A comparison with experimental data is given for potassium theoretically described by various potential functions.

Magnetic symmetry and transport properties of crystals

The forms of the galvanomagnetic and thermomagnetic property tensors appropriate to the 122 generalized crystal classes are discussed in the light of Kleiner's (1966-67) modified Onsager relations. The forms of the tensors of fourth rank are derived and discussed. The schemes for the grey groups are identical with those of the photoelastic tensor of the corresponding groups while the schemes for the single colour groups are similar to those of the magnetothermoelectric power tensor for the corresponding groups. 21 of the 58 two colour groups which contain the symmetry element 1 have schemes identical with those of the corresponding grey groups. The schemes for the remaining 37 groups which do not contain the symmetry element 1 are derived and presented here.

Magnetic symmetry and transport properties of crystals

The generalized Onsager relations applicable to transport property tensors for magnetic and non-magnetic crystals in the presence or absence of an external magnetic field were given by Kleiner. In this paper it is shown that the symmetry-restricted forms of the thermogalvanomagnetic property tensors conforming to Kleiner's prescription can be obtained from the forms of the polar and axial tensors appropriate to the 32 classical point groups, making use of the rules given by Birss for the equilibrium magnetic property tensors.