Conductivity Of Solid Solutions Research Articles

Thermal conductivity in solid solutions of lithium niobate tantalate single crystals from 300 K up to 1300 K

Lithium niobate tantalate (LiNb1−xTaxO3, LNT) solid solutions offer exciting new possibilities for applications ranging from optics, piezotronics, and electronics beyond the capabilities of the widely used singular compounds of lithium niobate (LiNbO3, LN) or lithium tantalate (LiTaO3, LT). Crystal growth of homogeneous LNT single crystals by the Czochralski method is still challenging. One key aspect of homogeneous growth is the accurate knowledge of thermal conductivity through the crystal boule during the growth, which is central to control the crystal growth. Therefore, the temperature dependent thermal conductivity of pure LN, LT, and LNT solid solutions, as well as of selected doped LN and LT crystals (Mg, Zn) was investigated across the temperature range from 300 to 1300 K. The results that span across the whole composition range can directly be applied for optimizing growth conditions of both LNT solid solutions as well as doped and undoped LN and LT crystals.

Effect of Synthetic Approaches and Sintering Additives upon Physicochemical and Electrophysical Properties of Solid Solutions in the System (CeO2)1−x(Nd2O3)x for Fuel Cell Electrolytes

Finely dispersed (CeO2)1−x(Nd2O3)x (x = 0.05, 0.10, 0.15, 0.20, 0.25) powders are synthesized via liquid-phase techniques based on the co-precipitation of hydroxides and co-crystallization of nitrates. The prepared powders are used to obtain ceramic materials comprising fluorite-like solid solutions with the coherent scattering region (CSR) of about 88 nm (upon annealing at 1300 °C) and open porosity in the range of 1–15%. The effect of the synthesis procedure and sintering additives (SiO2, ZnO) on physicochemical and electrophysical properties of the resulting ceramics is studied. The prepared materials are found to possess a predominantly ionic type of electric conductivity with ion transfer numbers ti = 0.96–0.71 in the temperature range of 300–700 °C. The conductivity in solid solutions follows a vacancy mechanism with σ700 °C = 0.48 × 10−2 S/cm. Physicochemical properties (density, open porosity, type and mechanism of electrical conductivity) of the obtained ceramic materials make them promising as solid oxide electrolytes for medium temperature fuel cells.

Synthesis and Characterization of Ceria- and Samaria-Based Powders and Solid Electrolytes as Promising Components of Solid Oxide Fuel Cells

Finely dispersed (CeO2)0.95(Sm2O3)0.05, (CeO2)0.90(Sm2O3)0.10 and (CeO2)0.80(Sm2O3)0.20 mesoporous powders with a specific pore volume of 0.080–0.092 cm3/g and a specific surface of 50–83 m2/g are synthesized by the co-precipitation of cerium and samarium hydroxides from the corresponding nitrate solutions. The prepared powders are used to obtain ceramic nanomaterials with a fluorite-like cubic crystal lattice with a coherent scattering region (CSR) of about 65–69 nm (1300 °C). The study of physicochemical and electrophysical properties of the prepared ceramics revealed the obtained materials featuring an open porosity of 2–6% and a predominantly ionic type of electric conductivity (ion transport numbers ti = 0.85–0.73 in the temperature range 300–700 °C). The conductivity in solid solutions proceeds via a vacancy mechanism with σ700 °C= 3.3·10−2 S/cm. The synthesized ceramic materials are shown to be promising as solid oxide electrolytes in medium temperature fuel cells.

Peculiarities of fluoride ion mobility and conductivity in solid solutions containing bismuth trifluoride, as studied by 19F NMR and impedance spectroscopies

Peculiarities of fluoride ion mobility and conductivity in solid solutions containing bismuth trifluoride, as studied by 19F NMR and impedance spectroscopies

Phase Equilibria in the Quasibinary Li2O⋅2B2O3–Yb2O3⋅B2O3 System, Assessment of Stability, and Conductivity of Solid Solutions Based on Li2O⋅2B2O3

Phase Equilibria in the Quasibinary Li2O⋅2B2O3–Yb2O3⋅B2O3 System, Assessment of Stability, and Conductivity of Solid Solutions Based on Li2O⋅2B2O3

Surface Morphology and Differential Tunneling Conductivity in Multicomponent Solid Solutions (Bi, Sb, Sn, Ge)2(Te, Se)3

The morphology of the interlayer surface and the spectra of differential tunneling conductivity in solid solutions (Bi, Sb, Sn, Ge)2(Te, Se)3 has been studied by scanning tunneling microscopy and scanning tunneling spectroscopy. Surface defects associated with distortions of surface electronic states as a result of atomic substitution and with the formation of intrinsic defects formed during the growth of solid solutions are systematized. The position of the Dirac point and its fluctuations relative to the mean value are determined, the levels of impurity surface defects are found, and their energy depending on the composition of the solid solution, the value of the Seebeck coefficient, and the power parameter are calculated. The surface concentration of Dirac fermions is calculated and the compositions are established in which the contribution of surface states increases due to an increase in the concentration of fermions and due to an increase in the Fermi velocity and mobility of fermions in the surface layer.

Synthesis and conductivity of solid solutions МxPb1–xSnF4–x (М=Li, Na, K, Rb)

Synthesis and conductivity of solid solutions МxPb1–xSnF4–x (М=Li, Na, K, Rb)

Conductivity of aliovalent substitution solid solutions Pb1-xRxSnF4+x (R = Y, La, Ce, Nd, Sm, Gd) with β-PbSnF4 structure

The electrical conductivity of Pb1-xRxSnF4+x solid solutions (R = Y, La, Ce, Nd, Sm, Gd), whose lattice is tetragonal and isostructural with β-PbSnF4, has been studied by 19F NMR and impedance spectroscopy. The ultimate percentage of cerium group RE fluorides in such solutions is not over 20.0 mol%, and that of gadolinium trifluoride reaches 12.0 mol%. The fluoride anions in the synthesized samples of Pb1-xRxSnF4+x solid solutions occupy, as in β-PbSnF4, three structurally nonequivalent positions. The charge transfer in complex fluorides of this type at temperatures above 350 K is done by interstitial fluoride ions. At a low substituent concentration (x ≤ 0.07), the electrical conductivity is almost an order of magnitude lower than that of β-PbSnF4. The conductivity of the synthesized solid solutions increases with increasing substituent content. The samples containing 10.0–15.0 mol% RF3 have the maximum conductivity. At the same RF3 content, the conductivity of solid solutions, except those containing gadolinium trifluoride, increases with decreasing R3+ radius (from La to Sm).

Ion mobility and transport properties of bismuth fluoride-containing solid solutions with tysonite-type structure

The ion mobility and conductivity of solid solutions with tysonite-type structure obtained by doping bismuth trifluoride with lead (II) fluoride, and zirconium and bismuth oxides have been studied using 19F NMR, X-ray diffraction analysis, and impedance spectroscopy. The types of ionic motions in the fluoride sublattice of the synthesized solid solutions in the temperature range 150–450 K have been determined and the energy of their activation has been estimated. Due to high ionic conductivity, above 10–2 S/cm at 570 K, these solid solutions can be considered as superionic conductors.

Ionic mobility and electrophysical properties of solid solutions in PbF2–SbF3 and PbF2–SnF2–SbF3 systems

Ionic mobility and electrical conductivity of solid solutions with fluorite structure, obtained with solid-state approach in PbF2–SbF3 and PbF2–SnF2–SbF3 systems, are studied by 19F NMR and electrochemical impedance spectroscopy methods. The 19F NMR spectra parameters, types of ion motions in the fluoride sublattice, and the ionic conductivity magnitude are shown to be determined by the temperature and fluoride concentration in the solid solutions. The solid solution specific conductivity in the PbF2–SbF3 and PbF2–SnF2–SbF3 systems at 420–450 K is as high as ~10–2 S/cm, which allows accounting the solid solutions as a base for preparation of functional materials.

Electrical conductivity in single crystals of GaSe x Te1 – x solid solutions in strong electrical fields

This paper presents some results of studying the Poole–Frenkel effect with allowance for shielding in layered GaSe and GaTe single crystals and their solid solutions in strong electrical fields of up to 105 V/cm at temperatures of 103–250 K. According to the relationship \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)} = E\sqrt{\frac{\varepsilon}{4\pi n(0)kT}}\), there exists a linear dependence between \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)}\) and the electrical field E (σ is the electrical conductivity in strong electrical fields, and σ(0) is the electrical conductivity in the ohmic region). The slopes of these lines have been determined at different temperatures (103–250 K) by estimating the concentration of current carriers n(0) = 3 × 1013–5 × 1015 cm–3 in the ohmic region of the electrical conductivity of solid solutions of layered GaSe x Te1–x single crystals (x = 1.00, 0.95, 0.90, 0.80, 0.70, 0.30, 0.20, 0.10, 0).

Transport properties of solid solutions PbF2–SnF2–SbF3 prepared by solid state techniques

The ionic mobility and electrical conductivity in solid solutions with the fluorite structure obtained by the solid-phase method in the system PbF2–SnF2–SbF3 with composition close to PbSnF4 have been investigated using the methods of 19F NMR and impedance spectroscopy. It has been established that parameters of 19F NMR spectra, types of ionic motions in the fluoride sublattice and the value of ionic conductivity are determined by temperature and the composition of the solid solutions. Transport properties of solid solutions under study are similar to those of tetragonal phase β-PbSnF4. It suggests that fluorite phase in solid solutions under study is metastable and formed by elementary fluorite-type blocks typical of the structure of β-PbSnF4. Introduction of Sb3+ into the structure leads to decrease in the conductivity. Nevertheless, the specific conductivity of solid solutions in the system and PbF2–SnF2–SbF3 at 400K attains the values of 10−2–10−3S/cm, which enables one to consider them as promising materials for electrochemical applications.

Structure and properties of solid solutions based on bismuth niobate Bi3NbO7

Solid solutions Bi3Nb1–y W y O7 ± δ, Bi3Nb1–y V y O7 ± δ, Bi3Nb1–y Fe y O7 ± δ (y = 0.1–0.5; Δy = 0.1), and Bi3–x Y x Nb1–y W y O7 ± δ (x = 0.05, 0.1; y = 0–0.3; Δy = 0.1) have been studied. The homogeneity ranges of the solid solutions and crystal-chemical parameters have been determined by means of X-ray powder diffraction. The electrical conductivity of sintered samples has been studied by impedance spectroscopy. The joint introduction of yttrium and tungsten into the niobium sublattice does not lead to an increase in the conductivity of solid solutions, and the change of the dopant type has no noticeable effect on this conductivity.

T–x phase diagram and electrical conductivity of solid solutions in the TlInSe2–TlGaTe2 system

Using detailed physicochemical characterization results, we have mapped out the T–x phase diagram of the TlInSe2–TlGaTe2 system. The system has been shown to have eutectic phase relations, with limited solid solubilities of its constituent components. The extent of the TlInSe2-based solid solution is 30.0 mol %, and that of the TlGaTe2-based solid solution is 25.0 mol %. The eutectic is located at 55.0 mol % TlGaTe2 and melts at a temperature of 973 K. The electrical conductivity of crystalline samples of the solid solutions has been measured as a function of temperature.

Ion mobility and conductivity in solid solutions in the KBiF4–ZrF4 system

The ion mobility and conductivity in solid solutions with the fluorite structure (100–x)KBiF4 + xZrF4, where x = 2.5–15 mol %, is studied by the methods of differential scanning calorimetry (DSC), X-ray diffraction (XRD), and 19F NMR. The character and type of ion transport in the fluorite sublattice of solid solutions are studied as well as the temperature intervals in which it is observed (150–570 K). For solid solutions containing 5 and 10 mol % ZrF4, the fluorine ion diffusion coefficient is assessed. It is found that the conductivity in the solid solution systematically decreases as the content of zirconium tetrafluoride in the sample decreases, which is probably due to the formation of strongly bound complexes formed by interstitial fluoride ions with zirconium cations. The presence of the high ionic conductivity in the tested solid solutions (from ~10–3 to 10–2 S/cm) makes this material a good candidate for preparation of materials with the high ion-conducting properties.

Structure and ionic conductivity of solid solutions in the K2CO3-AgNO3-Sb2O3-MeO3 System (Me = W or Mo)

Specific features of the formation of solid solutions in the xAgNO3-(y − x)K2CO3-ySb2O3-2(2−y)MeO3 system (Me = W or Mo, 0 ≤ x ≤ y, 1.0 ≤ y ≤ 2.0) are studied. For a temperature of 1123 K, the single-phase region of complex antimony(V) oxides containing potassium and silver ions with a pyrochlore-type structure is determined in the concentration triangles KSbO3-MeO3-AgSbO3 (Me = W or Mo). A model of the ion filling of a regular system of points within the space group Fd3m is proposed and confirmed by full-profile analysis. A relationship between pyrochlore phases and ion-conducting properties is established.

Structural and transport characteristics of substituted bismuth niobates

The results of studying solid solutions with the composition of Bi3Nb1 − y Zr y O7 ± δ, Bi2.95Y0.05Nb1 − y Zr y O7 ± δ (y = 0–0.5; Δy = 0.1), and Bi6.95Y0.05Nb2 − y Zr y O15.5 (y = 0.1–1; Δy = 0.1) are presented. XRD and electron microscopy with X-ray microanalysis are used to determine the homogeneity regions of solid solutions; crystallochemical parameters are calculated. It is shown that irrespective of the ratio of Bi: Nb, two cubic phases are formed at an increase in the dopant amount. One of these represents a solid solution based on Bi3NbO7 (δ-phase) and the second one is a solid solution based on δ-Bi2O3 (δ′-phase). Conductivity of sintered samples is studied using the impedance spectroscopy technique. Introduction of yttrium into the bismuth sublattice results in no increase in conductivity of solid solutions, while in the case of the ratio of Bi: Nb = 3: 1, overall conductivity of solid solutions is somewhat higher at similar dopant concentrations.

Electric conductivity of solid solutions in Cs2 − 2x Fe2 − x A x O4 systems (A = P, V)

Solid solutions based on CsFeO2 in Cs2 − 2x Fe2 − x A x O4 systems (A = P, V) were synthesized. Their crystal structure and the temperature and concentration dependences of the total conductivity and its electronic component were studied. The ranges of temperature and composition in which cesium-cation conductivity was dominant were determined. The obtained data were compared with the results of studies of other cesium-conducting solid electrolytes.

Temperature and concentration dependences of thermal conductivity of solid solutions of gadolinium and dysprosium sulfides

Thermal conductivity of a number of solid solutions of gadolinium and dysprosium sulfides has been studied experimentally within the temperature range 80-400 K. The work offers the data on thermal conductivity coefficient and lattice thermal conductivity of the studied samples. It was found that replacement of gadolinium ions by dysprosium ions leads to significant decrease of the samples’ thermal conductivity and changes its temperature dependence character due to the resonance scattering of phonons by paramagnetic ions of dysprosium. Influence of this mechanism of phonon scattering conditions the area of anomalous change observed on the concentration dependence of thermal conductivity coefficient.

Melting behaviour, morphology and conductivity of solid solutions of PEO/PAc blends and LiClO4

The melting behaviours of poly(ethylene oxide)/polyacrylate (PEO/PAc) and PEO/PAc doped with LiClO4 were investigated by differential scanning calorimetry. The equilibrium melting temperature and the crystallinity of PEO show no significant variation with the addition of PAc but are suppressed by the incorporation of LiClO4. The deformed structure of PEO spherulite resulting from disrupted crystallisation is observed in salt doped PEO and its blends. Conductivity as a function of salt concentration is studied using the power law. Lower ion mobility and correlation of ions for PAc corroborate with its lower conductivity as compared to PEO. Despite a reasonable amount of LiClO4 being solvated by PAc, the conductivity of the solid solutions of PEO/PAc blends is primarily governed by PEO.