Electrical conductivity of Na2SO4(I)

The electrical conductivity of the solid phase Na₂SO₄(I) has been measured between the melting point at 884°C and the first order phase transition at about 240°C. The measurements have been performed using complex impedance measurements on pellet samples as well as on U-cells. The electrical conductivity is strongly dependent on sample at low temperatures and the activation energy ranges from 0.5 eV to 1.7 eV over the measured temperature range.     

Effect of deuteration on the electrical conductivity,dielectric constant and phase transitions in LiNH4SO4

Measurements of dc conductivity and dielectric constant show that deuteration causes an upward shift of the high temperature phase transition point from 186.5 to 191°C and a downward shift of the low temperature transition point from 10 to -1.5°C in LiNH₄SO₄. Mechanisms of phase transitions and of electrical transport in the crystal are discussed.     

Hot stage X-ray diffractometer studies on Ag2PbI4 and Ag4PbI6

Mixtures of AgI and PbI₂ cooled from the melt result in the peritectic formation of a fast ion conducting phase centred about Ag₄PbI₆, which is face centred cubic with a = 6.33(5)A; this phase exhibits high electrical conductivity. On cooling to about 125°C, dissociation occurs to γAgI and PbI₂, accompanied by the transient formation of another phase, centred about Ag₂PbI₄. A modified form of the T-x section of the equilibrium phase diagram at AgI concentrations greater than 60 mole % and below 300°C is proposed.     

New Li+ ion conductors in the system Li4SiO4−Li3AsO4

In the system Li₄SiO₄-Li₃AsO₄, Li₄SiO₄ forms a short range of solid solutions containing up to 14 to 20% Li₃AsO ₄, depending on temperature, and γ-Li₃AsO₄ forms a more extensive range of solid solutions containing up to ≈55% Li₄SiO₄. The Li₄SiO₄-Li₃AsO₄ phase diagram has been determined and is of binary eutectic character. The ac conductivity of polycrystalline samples was measured over the range 0 to at least 300°C for nine different compositions. The two solid solution series have much higher conductivity than the pure end-members; maximum conductivity was observed in the γ-Li₃AsO₄ solid solutions containing ≈40 to 55% Li₄SiO₄, with values of $\text{≈2×10}{}^{\mathrm{?6}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 20°C rising to ≈0.02 Ω^?1 cm^?1 at 300°C. These values are comparable to those found in the system Li₄SiO₄-Li₃PO₄. The variation with composition of the Arrhenius prefactor and activation energy has been interpreted in terms of the mechanisms of conduction. Li₃AsO₄ is a poor conductor essentially because the number of mobile Li⁺ ions is very small. This number, and hence the conductivity, increases dramatically on forming solid solutions with Li₄SiO₄, by the creation of interstitial Li⁺ ions. At ≈40 to 55% Li₄SiO₄, the number of mobile Li⁺ ions appears to be optimised. An explanation for the change in activation energy of conduction at ≈290°C in Li₄SiO₄ and at higher temperatures in Li₄SiO₄ solid solutions is given in terms of order-disorder of the Li⁺ ions.     

Low temperature electrical conductivity,dielectric constant,and phase transitions in (NH4)2SO4 and (ND4)2SO4

Careful axiswise measurements of d.c. conductivity and dielectric constants of (NH₄)₂SO₄ from 50 to - 196°C establish two distinct phase transitions, instead of one, at temperatures -49.5 and -58°C which remain unchanged in (ND₄)₂SO₄. Explanation based on successive distortions of non-equivalent (NH₄)⁺ is offered. Low temperature transport process in the crystal also is discussed.     

Mn3O4包覆对LiNi0.5Mn1.5O4正极材料界面电化学性能的提高

本文采用化学湿磨法,首次将金属氧化物Mn₃O₄包覆于LiNi_0.5Mn_1.5O₄颗粒表面,使得电极材料的电子电导率从1.53×10^-7 S/cm 提高到3.15×10^-5 S/cm. 电化学测试结果表明Mn₃O₄包覆大大提高LiNi_0.5Mn_1.5O₄正极材料的倍率性能和高温循环稳定性. 最佳包覆样品为2.6wt% Mn₃O₄包覆的LiNi_0.5Mn_1.5O₄,在10 C倍率下具有108 mAh/g的高放电容并且在55 °C下100次循环后仍有78%的容量保持率,远大于未包覆样品67%的容量保持率.     

Effect of plastic deformation on the electrical conductivity of NH4Cl

Excess electrical conductivity is induced by plastic deformation in NH₄Cl crystals. Study of the isothermal annealing of the excess conductivity at different temperatures in the range 80–150°C gives an activation energy of 0.08 eV for the carrier responsible for excess conduction, which is suggested to be a proton.     

High temperature phase transition in NH4H2PO4

NH₄H₂PO₄ (ADP) has been investigated by infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and d.c. conductivity in the temperature range of 25–180° C. Sharp reversible changes were observed in the region from 400 to 500 cm^?1 of the infrared spectra in the temperature range of 138–174° C. Similar and supportive data were obtained with DSC, TGA and DC conductivity measurements. The results clearly suggest a high temperature phase transition for ADP before its melting point.     

Conductivity enhancement of lithium bromide monohydrate by Al2O3 particles

Lithium bromide monohydrate, LiBr · H₂O, shows an electrical conductivity of 1.4 × 10^-4 mho cm^-1 at 100°C and an activation energy of 57 kJ/mol. If Al₂O₃ particles are dispersed into this phase, the conductivity is enhanced by nearly one order of magnitude, but the activation energy remains the same. This result is compatible with a depletion-layer mechanism, but not with the formation of a higher hydrate.     

Anomalous acid proton self-diffusion in N(CH3)4HSO4 — A candidate for proton superionic conductivity

The appearance of a “liquid-like” proton T₂ component above 100°C and the relatively high value of the proton self-diffusion coefficient D = (5–8) × 10^-7cm²sec^-1 between 175°C and 200°C demonstrate the onset of a super-ionic state in N(CH₃)₄HSO₄. The ratio between the “liquid” and “solid” like components shows that acid protons are responsible for the high ionic conductivity.     

Li ion conduction in Li2ZrO3, Li4ZrO4, and LiScO2

The results of ac and dc conductivity measurements on Li₂ZrO₃, Li₄ZrO₄, and LiScO₂ show that these phases are Li ion conductors. Even though the Li ion conductivity in these phases is quite low, 3.3×10^?5, 3.0×10^?4, and 4.2×10^?7 S m^?1 at 573 K, respectively, they are of special interest since they are among the small group of ternary oxides which may be thermodynamically stable against Li. Mechanisms are proposed for the decomposition of these phases at the anode due to Li loss during dc polarization. In addition the electrical conductivity of ternary oxide phases which are, or may be, thermodynamically stable against Li are summarized.     

Li4SiO4-Li3VO4赝二元系和Li4GeO4-Li4SiO4-Li3VO4赝三元系中新的锂离子导体

本文在室温到300℃的温度范围内研究了Li₄SiO₄-Li₃VO₄和Li₄GeO₄-Li₄SiO₄-Li₃VO₄体系中的离子导电性,发现γ_II相固溶体Li_3+xV_1-xSi_xO₄是好的锂离子导体。所研究的成分中Li_3.3V_0.7Si_0.3O₄的离子电导率最高,室温下为1×10^-5Ω^-1·cm^-1,在42—192℃的电导激活能为0.36eV,电子电导率可以忽略,因而这是迄今所发现的最好的锂离子导体之一。粗略确定了Li₄GeO₄-Li₄SiO₄-Li₃VO₄三元系中电导率高的范围,发现在Li_3.5V_0.5Ge_0.5O₄中Si部分取代Ge可以使电导率进一步提高,Li_3.5V_0.5Ge_0.4Si_0.1O₄的室温电导率可达1.3×10^-5Ω^-1·cm^-1,电导激活能为0.40eV。 关键词：     

Ionic transport in the lithium nitride bromides,Li6NBr3 and Li1 3N4Br

The ionic and electronic conductivities of the lithium nitride bromides Li₆NBr₃ and Li_{1 3}N₄Br have been studied in the temperature range from 50 to 220°C and 120 to 450°C, respectively. Both compounds are practically pure lithium ion conductors with negligible electronic contribution. Li₆NBr₃ has an ionic conductivity Ω of 2 × 10^-6Ω^-1cm^-1 at 100°C and an activation enthalpy for σT of 0.46 eV. Li_{1 3}N₄Br shows a phase transition at about 230°C. The activation enthalpy for σT is 0.73 eV below and 0.47 eV above this temperature. The conductivities at 150 and 300°C were found to be 3.5 × 10^-6 Ω^-1cm^-1 and 1.4 × 10^-3Ω^-1cm^-1, respectively. The crystal structure is hexagonal at room temperature with $\text{a = 7.415 (1)}\text{A}\text{?}$ and $\text{c = 3.865 (1)}\text{A}\text{?}$.     

Electrochemical properties of LiFe0.9Mg0.1PO4 / carbon cathode materials prepared by ultrasonic spray pyrolysis

The LiFe_0.9Mg_0.1PO₄/C powder of pure olivine phase can be prepared with the duplex process of spray pyrolysis synthesis (at 450 ^°C) and subsequent heat treatment (at 700 ^°C for 2, 4 and 8 h). From scanning electron microscopy observation with corresponding elemental mapping images of iron, phosphorous and magnesium, it could be found that the LiFe_0.9Mg_0.1PO₄ powders are covered with fine pyrolyzed carbon. Raman spectra indicate that the phase of carbon with higher electronic conductive phase is predominant when prolonged subsequent heat treatment is carried out. The carbon coatings on the LiFe_0.9Mg_0.1PO₄ surface can improve the conductivity of the LiFe_0.9Mg_0.1PO₄ powder (3.8×10⁻⁵ S cm⁻¹) to about a factor of ∼10⁴ higher than the conductivity of LiFePO₄. The stability and cycle life of a charge/discharge cycle test of lithium ion secondary batteries are also enhanced. The results indicate that the LiFe_0.9Mg_0.1PO₄ powder, prepared at a pyrolysis temperature of 450 ^°C and with post-heat-treatment at 700 ^°C for 8 h, exhibits a specific initial discharge capacity of about 132 mA h g⁻¹ at C/10 rate, 105 mA h g⁻¹ at 1C, and 87 mA h g⁻¹ at 5C.     

Conductivity of the solid electrolyte RbAg4I5 in the microwave region

The high frequency ionic conductivity of RbAg₄I₅ single crystals was measured in the range from 0.1 MHz to 8 GHz using a microwave reflection method. In the whole temperature region studied (30°C to 135°C) the bulk conductivity was found to be frequency independent and to coincide with the latest published values for the static conductivity. This result is in contradiction with values reported formerly in literature but agrees very well with recent measurements on the structurally similar solid electrolyte AgI.     

Frequency and temperature-dependent electrical properties of LiNi3/5Fe2/5VO4 studied by complex impedance spectroscopy

The LiNi_3/5Fe_2/5VO₄ has been synthesized by solution-based chemical method. Grain morphology of the material is investigated using field emission scanning electron microscopy. The existence of electrical conduction due to bulk and grain boundary effects at 21, 75 and 250 °C, and grain boundary and polarization effects at 275 and 300 °C has been verified by impedance spectroscopy. DC conductivity shows electrical conduction in the material as a thermally activated process. The frequency dependence of AC conductivity is described by Jonscher's power law.     

Ionic conductivity in Na4ZrSi3O10

A new compound, Na₄ZrSi₃O₁₀, belonging to the ternary system Na₂O-SiO₂-ZrO₂ is presented. Based on X-ray powder methods, it is assigned monoclinic symmetry with the probable group C 2/c. The ionic conductivity was found to be 4 x 10^-3Ω^-1cm^-1 at 300°C and the activation energy for ionic motion is 42 kJ/mol.     

Preparation and properties of a new polytype of tantalum disulfide (4Hb-TaS2)

A new polymorph of the layered compound tantalum disulfide, 4Hb-TaS₂, has been prepared in single crystal form. Measurements of magnetic susceptibility, electrical resistivity, and differential heat capacity show two first order transitions at 20 and 315°K. The 315°K transition involves only a small volume and enthalpy change, as in the previously observed transitions of another polymorph, 1T-TaS₂. The resistivity measurements show metallic like conductivity, as in 2H-TaS₂, when the current is parallel to the layers, but semiconducting like conductivity, as in 1T-TaS₂, when perpendicular to the layers. The properties of 4Hb-TaS₂ are moderately well described as a ‘mix’ of those of 1T-TaS₂ and 2H-TaS₂.     

Thermoelectric power of (Me4N)2Ag13I15 and (Et4N)2Ag13I15

Thermoelectric power using reversible silver electrodes and electrical conductivity on the compressed pellets of (Me₄N)₂Ag₁₃I₁₅, and (Et₄N)₂Ag₁₃I₁₅ have been measured between room temperature and below 160°C. The results of θ can be expressed by the equations:?θ = 0.115 (10³/T)+0.2905VK^?1 and ?θ = 0.150 (10³/T) + 0.305mV K^?1; and those of conductivity by the equations; σ = 28.7 exp (?0.17eV/kT) ohm^?1cm^?1 and $\text{σ = 216.6 exp (?0.24e}\text{V}\text{kT}\text{)}$ ohm^?1cm^?1; respectively for Me- and Et-electrolytes. The results are discussed and compared with those of previous authors.     

Proton conduction in (NH4)3 H(SO4)2 single crystals

D.C. electrical conductivity, DTA and coulometric studies on (NH₄)₃ H(SO₄)₂ single crystals are made. Conductivity is markedly anisotropic with maximum along c¹ direction. A sudden jump in the conductivity plot along c¹ direction at 413 K is supported by a large endothermic peak in DTA, confirming the presence of transition at this temperature. The values of activation energy calculated from conductivity measurements indicated that the charge carriers are protons. This was further confirmed by coulometric experiment where the gas evolved was hydrogen, as established by a gas chromatograph and the volume of H₂ released agreed with that expected from electrolysis. The mechanism of protonic conduction in this crystal is discussed.