Electroconductance of single-crystal Li2 + x Fe 2 − 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22)

Electrophysical properties of single-crystal Li_{2 + x} Fe _{2 ? 2x} ²⁺ Fe _x ³⁺ (MoO₄)₃ (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10^-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li_2.22Fe _1.56 ²⁺ Fe _0.22 ³⁺ (MoO₄)₃ is markedly anisotropic.     

Preparation and characterization of Ca1 − x Ce x MnO3 perovskite electrodes

The electrochemical properties of Ca_1 − x Ce _x MnO₃ perovskite-type oxide electrode have been investigated by cyclic voltammetry in Na₂SO₄ aqueous solutions with pH 14. The structural and morphological characterizations have also been investigated and the information used to interpret the electrochemical behavior. An estimation of the electrode’s capacitance and roughness factor has been obtained by means of cyclic voltammetry. The specific capacitance and consequently the roughness factor values are affected by the presence of Ce ions in the oxide. These findings are in agreement with the increase of the oxide-specific surface area by the introduction of Ce ion. The open-circuit potential and the voltammetric patterns are dependent on the presence of Ce ion in the electrodes and support that the surface electrochemistry of the perovskite oxide electrodes is governed by the Mn⁴⁺–Mn³⁺ redox couple.     

Hydrogen content in proton-conducting perovskites CaZr1 − x Sc x O3 − x /2 (x = 0.0–0.2)

The hydrogen content in CaZr_{1 ? x} Sc _x O_{3 ? x/2} (x = 0.00–0.20) and BaZr_0.9Y_0.1O_3-α (for comparison) was studied by powder nuclear microanalysis. The samples were saturated with heavy water (D₂O) vapors at 350 and 400°C in air. The chemical expansion of the CaZr_0.95Sc_0.05O_3-α and BaZr_0.95Y_0.05O_3-α samples at 700°C was measured at different water vapor pressures. A model was suggested to explain the lowered hydrogen content in oxides based on CaZrO₃.     

Gas-sensing properties of Ta-doped MoO3−x

During a search for alternative materials to replace tin(IV) oxide in semiconducting oxide gas sensors it has been found that sensors comprising sub-stoichiometric molybdenum trioxide exhibit promising characteristics.     

Atoms state and interatomic interactions in perovskite-like oxides: XXXII. Formation of paramagnetic clusters in the La1−0.33x Ca0.33x Fe x Al1−x O3 and La1−0.33x Sr0.33x Fe x Al1−x O3 solid solutions

Calcium- and strontium-containing lanthanum orthoferrites have been studied using magnetic dilution method. It has been shown that the iron-atom clusters with competing ferro- and antiferromagnetic exchange interactions can exist. By using Mossbauer spectroscopy, Fe(IV) atoms have been found in the La_1?0.33x Ca_0.33x Fe_xAl_1?x O₃ solid solutions and Fe(III) atoms in two different surroundings have been found in the La_1?0.33x Sr_0.33x Fe _x Al_1?x O₃ solid solutions. The compositions of paramagnetic clusters stable at the infinite dilution have been proposed basing of the magnetic susceptibility and Mossbauer spectroscopy data.     

Potassium-conducting solid electrolytes in the K3 − 2x Cd x PO4 system

New potassium-conducting solid electrolytes of the K_{3 ? 2x} Cd _x PO₄ system are synthesized and studied. A wide range of solid solutions reaching x ≈ 0.35 with the structure of high-temperature modification of potassium orthophosphate forms in the system. An addition of cadmium ions leads to an abrupt increase in the K₃PO₄ conductivity due to the formation of potassium vacancies. The highest conductivity is approximately 10^?2 S cm^?1 at 300°C and above 10^?1 S cm^?1 at 700°C.     

Longitudinal conductivity of thin films of La1 − x Sr x F3 − x solid solutions on glass ceramics

The longitudinal conductivity of La_{1 ? x} Sr _x F_{3 ? x} solid solution films (x = 0–0.24) with thicknesses of 40–260 nm grown on glass ceramics at temperatures from room temperature to 300°C and frequencies of 10^?1–10⁶ Hz was studied by impedance spectroscopy. The concentration dependence of film conductivity on the SrF₂ content had a maximum near x = 0.05. An equivalent circuit was constructed on the basis of the impedance plots to describe migration processes. The DC conductivity was evaluated for all samples under study. The activation energies were estimated from the temperature dependences of the DC conductivities of the films. The resulting dependences of electrophysical parameters were compared with those for bulk materials in terms of the relaxation conductivity model.     

Phase Transitions in the BaCe1–x Nd x O3–δ System (x = 0–0.15)

Phase transitions in BaCe_{1 – x} Nd _x O_3– (x = 0–0.15) are studied on ceramic samples by dilatometry (at 370–1100 K) and by measuring electroconductivity (at 750–1220 K). Ion transport numbers are measured by an EMF method at 850–1240 K. All measurements are done in dry air (₂ 40 Pa). By treating the obtained temperature dependences of linear expansion with a difference method (difference between first-degree polynomial approximating the dependence and experimental points), the position and the sort of the phase transitions are determined. High-temperature phase transitions are confirmed by measuring the electroconductivity and ion transport numbers. Second-order phase transitions in pure BaCeO₃ are discovered at 480 ± 10, 530 ± 10, 900 ± 10, 1030 ± 20, and 1170 ± 10 K and a first-order transition, at 665 ±10 K. Phase transitions at 900 and 1030 K are discovered for the first time ever.     

Lithium-cation Conduction and Crystallochemical Features of Solid Solutions La2/3 – x Li3x□4/3 – 2x Nb2O6 with the Structure of Fault Perovskite

Transport properties and crystallochemical features of lithium-containing lanthanum metaniobates La_{2/3 – x} Li_{3x4/3 – 2x} Nb₂O₆ with the structure of fault perovskite are studied. The materials studied have high conductivity by lithium ions. A correlation between the conductivity magnitude, chemical composition, and crystallographic parameters is found.     

Multivariate analysis of melting points for homologous series C x H2x − 1NO (x = 3−6)

A multivariate analysis of the empirical structure data for isomeric homologues using principal-component analysis has been carried out, and the correlation with experimental melting points has been shown. Based on the data on the CSD structure, we discuss the impact of molecular H-aggregation.     

Crystal structure of Ag2TeS3 and Na(Na1−x Ag x )TeS3 (x≈0.5) and the geometry of Te(IV)S3 polyhedra

Summary Structural data determined by single crystal X-ray experiments (T=300 K) are reported for Ag₂TeS₃ (monoclinic, Cc-C _s ⁴ ;a=6.783(1),b=11.567(2),c=7.693(1) Å; =114.44(1)°;Z=4;R=0.044) and for Na(Na_1–x Ag _x )TeS₃ x0.5; monoclinic, P2₁/c-C _2h ⁵ ;a=5.761(9),b=12.171(8),c=8.342(4) Å; =92.26(6)°;Z=4;R=0.030). In both compounds the atomic arrangements are characterized by isolated trigonal pyramidal TeS₃ polyhedra, irregularly coordinated Ag and Na atoms forming AgS₄ and (Na, Ag)S₄ polyhedra, and slightly distorted NaS₆ octahedra. Crystals of both compounds were synthesized under moderate hydrothermal conditions from an equimolar mixture of the elements in concentrated aqueous ammonia and 5N NaOH solution, respectively.

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Kristallstruktur von Ag₂TeS₃ und Na(Na_1–x Ag _x )TeS₃ (x0.5) nebst einem Vergleich der Geometrie von TeS₃-Gruppen

Zusammenfassung Es wird über die mittels Röntgenbeugungsexperimenten an Einkristallen bei 300 K bestimmten Strukturen von Ag₂TeS₃ (monoklin Cc-C _s ⁴ ;a=6.783(1),b=11.567(2),c=7.693(1) Å; =114.44(1)°;Z=4;R=0.044) und Na(Na_1–x Ag _x )TeS₃ (x0.5; monoklin, P2₁/c-C _2h ⁵ ;a=5.761(9),b=12.171(8),c=8.342(4)Å; =92.26(6)°;Z=4;R=0.030) berichtet. In beiden Verbindungen ist die Atomanordnung durch isolierte trigonal-pyramidale TeS₃-Polyeder, unregelmäßig koordinierte Ag- und Na-Atome, AgS₄- und (Na, Ag)S₄-Polyeder bildend, sowie leicht verzerrte NaS₆-Oktaeder charakterisiert. Kristalle der beiden Verbindungen wurden unter moderaten Hydrothermalbedingungen aus einem equimolaren Gemenge der Elemente und konzentrierter wäßriger Ammoniaklösung bzw. 5N NaOH-Lösung gezüchtet.

     

Synthesis and electrochemical properties of nanosized carbon-coated Li1−3x La x FePO4 composites

Nanosized carbon-coated Li_1−3x La _x FePO₄ composites were synthesized using a fast, easy, microwave assisted, room-temperature, solid-state method. A lanthanum precursor was used to improve the electronic conductivity of LiFePO₄. The particle structure of the as-synthesized samples was observed using transmission electron microscopy. The results indicated that a uniform and continuous carbon layer was formed on the surface of Li_1−3x La _x FePO₄ particles. Electrochemical techniques, such as cyclic voltammetry, charge/discharge test, and electrochemical impedance spectroscopy were used to investigate the electrochemical performance of the samples. The results of electrochemical measurements revealed that the carbon coating and lanthanum doping provided an initial discharge capacity of 145 mA h/g with excellent rate capacity and long cycling stability. These advantages, coupled with the low cost, the high thermal stability, and the environmental friendliness of the raw materials, render Li_1−3x La _x FePO₄/C composites attractive for practical and large-scale applications.     

A Density Functional Study of Small （NiTi）x Clusters with x=1-3

Systematic studies on the geometry, electronic structure and vibrational properties of small (NiTi)x clusters with x=1-3, within the framework of the density functional theory, were performed in this work. The electronic structure analyses were used to investigate the bonding between the early-late(EL) transition metals in their alloy. The results of our calculations have been used to predict (NiTi)x clusters structure for the ground state and confirm that s-electron density is transferred from Ti atoms to Ni atoms followed by the back donation of electrons through the d-orbital. The study provides a fragment approach based on the isolobal analogy that NiTi molecular fragments play a significant role in forming clusters.     

Phase equilibriums, oxygen exchange kinetics and diffusion in oxides CaZr1 ? x Sc x O3 ? x/2 ? δ

Oxides CaZr_{1 ? x} Sc _x O_{3 ? x/2 - ??} (x = 0.00?C0.20) were synthesized according to the ceramic technology. The solubility boundary of scandium with formation of solid solutions on the basis of calcium zirconate CaZrO_{3 ? ??} corresponds to x = 0.07?C0.08. The second phase of CaSc₂O₄ is present in the samples with scandium content of x = 0.10, 0.15, 0.20. Its fraction grows at an increase in x. The method of full-profile Rietveld analysis was used to calculate the structure parameters for oxides CaZr_0.99Sc_0.01O_{2.995 ? ??} and CaZr_0.95Sc_0.05O_{2.975 ? ??}. The method of isotopic exchange with gas phase analysis was used to study the kinetics of gas-phase oxygen interaction with the CaZr_0.95Sc_0.05O_{2.975 ? ??} oxide in the temperature range of 700?C850°C and at oxygen pressures of 0.13?C6.67 kPa. The values of effective activation energies of the oxygen exchange and diffusion processes were 1.36 ± 0.32 and 1.92 ± 0.21 eV, accordingly. The dependence of the interphase exchange rate on the pressure of oxygen corresponds to the power law with the exponent of 0.31 ± 0.04 at the temperature of 750°C.     

Electrical and electro-chemical characterisation of La0.99Fe1−x Ni x O3−δ perovskites

(LFN, 0<x<0.6) perovskites were synthesised by a solid-state route and were characterised by powder XRD, dilatometry, four-point DC conductivity measurements and electro-chemical impedance spectroscopy (EIS) on cone-shaped electrodes using a Ce_1.9Gd_0.1O_1.95 (CGO10) electrolyte. All the compounds were of single phase, and they belong to either the cubic or the hexagonal crystal system. The thermal expansion coefficient (TEC) was in the range 10.7*10⁻⁶ K⁻¹ to 13.4*10⁻⁶ K⁻¹, which continued to increase with increasing nickel content. The highest electronic conductivity was measured for the composition giving a value of 670 S/cm at 380 °C. The highest electro-chemical performance was measured for the composition giving an area specific resistance as low as 5.5 Ωcm² at 600 °C based on EIS measurements on a cone-shaped electrode. Composite cathodes made from and CGO10 revealed a rather low performance due to an un-optimised micro-structure.

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Positron annihilation studies in YBa2Cu3O x (6<x≤7)

Positron lifetime and Doppler broadening of the annihilation line measurements, as a function of temperature between 14 and 300 K, have been performed on four YBa₂Cu₃O _x (6<x7) samples with different oxygen deficiency. It was found that the positron lifetime and theS parameter values increase as the oxygen deficiency increases in the YBa₂Cu₃O _x (6<x7) samples. It was also observed that the positron annihilation parameers show different temperature dependence in the YBa₂Cu₃O _x (6<x7) samples associated with their different oxygen deficiency.     

Synthesis and photoluminescent properties of Y1 − x La x PO4:Eu3+ nanophosphor

In this paper, Y_{1 ? x} La _x PO₄:Eu³⁺ (x = 0.5, 0.7, and 0.3) nanophosphors were synthesized by a rather simple method. The products present different morphologies. For Y_{1 ? x} La _x PO₄:Eu³⁺, they have similar phase composition of a mixture of monoclinic LaPO₄ and tetragonal YPO₄. Furthermore, the luminescence behavior of Eu³⁺ has been investigated in this type of matrices. In Y_{1 ? x} La _x PO₄:Eu³⁺, the ⁵D₀-⁷F₁ magnetic dipole transition is dominant, indicating that the Eu³⁺ site is inversion symmetry. The difference in the Eu-O charge transfer (CT) band with La³⁺ ion concentration suggests the difference in the ionicity of the Eu-O bond. Among those products, the red to orange intensity ratio (R/O) of ⁵D₀-⁷F₂ to ⁵D₀-⁷F₁ value of Eu³⁺ is different, furthermore, for La³⁺ x = 0.3, the R/O value of Eu³⁺ is the biggest on the contrary, indicating that the inversion symmetry Eu³⁺ is lowest.     

Formation of (C x H2x+1)4NBr·nH2O (x = 1–3) hydrate

The phase diagram of the binary system tetramethylammonium bromide-water was studied by the differential thermal analysis. In the stable region two phases, ice and the salt itself, were detected, and in the metastable region, three tetramethylammonium bromide hydrates (bromide-water, 1 : 4, mp 68.8°C, 1 : 5, mp 36.0°C, 1 : 7.5, mp ?19.5°C) were found. Formation of (C _x H_2x+1)₄NBr·nH₂O (x = 1–3, n = 4, 5, 7.5) hydrates was revealed.     

High-pressure synthesis and local structure of corundum-type In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.7)

The corundum-type In(2-2x)Zn(x)Sn(x)O(3) solid solution (cor-ZITO, x ≤ 0.7) was synthesized at 1000 °C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO(3). Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO(3)-type arrangement.     

Formation of helium cluster ions HHe x + (x≦14) and H3He x + (x≦13) in a very low temperature drift tube

The formation of cluster ions when hydrogen molecular ions H ₂ ⁺ and H ₃ ⁺ are injected into a drift tube filled with helium gas at 4.4 K has been investigated. When H ₂ ⁺ ions are injected, cluster ions HHe _x ⁺ (x≦14) are produced. No production of H₂He _x ⁺ ions is observed. When H ₃ ⁺ ions are injected, cluster ions HHe _x ⁺ (x≦14) are produced as well as H₃He _x ⁺ (x≦13), and very small signals corresponding to H₂He _x ⁺ (3≦x≦10) are observed. Information on the stability of HHe _x ⁺ and H₃He _x ⁺ is derived from the drift field dependence of the cluster size distributions. The cluster sizex=13 is found to be a magic number for HHe _x ⁺ , and for H₃He _x ⁺ ,x=10 and 11.