The effect of sulfide substitution in the mixed conductor Cu7PSe6

Cu₇PSe₆ is a mixed conductor exhibiting structural phase transitions above and below room temperature that are accompanied by step-like changes in electrical conductivity. The substitution of S²⁻ for Se²⁻ in Cu₇PSe₆ significantly enhances electrical conductivity at room temperature compared to that observed for the pure compound. In the case of Cu₇P(Se_0.80S_0.20)₆, a nearly temperature-independent electrical conductivity exceeds 1 S/cm with no evidence of any phase transitions throughout the temperature interval 200-400 K. However, the ionic contribution accounts for just 2% of the total electrical conductivity in this solid solution at room temperature.     

Electrical conductivities of the Ag6PS5X and the Cu6PSe5X (X=Br, I) argyrodites

The Ag₆PS₅Br and Ag₆PS₅I argyrodites crystallize in a face-centered-cubic lattice at room temperature. Both compounds exhibit purely Arrhenius behavior throughout the temperature range 150-400 K with similar activation energies of about 0.23 eV. Cu₆PSe₅Br and Cu₆PSe₅I also crystallize in a face-centered-cubic structure at room temperature. Cu₆PSe₅Br exhibits a distinctive anomaly in electrical conductivity near 286 K while Cu₆PSe₅I undergoes a first-order electrical phase transition near 265 K. Their activation energies above room temperature are 0.13 and 0.30 eV, respectively.     

Electrical properties of the Ag6PSe5X (X=Cl, Br, I) argyrodites

The total electrical conductivities at room temperature of Ag₆PSe₅Cl, Ag₆PSe₅Br, and Ag₆PSe₅I were found to be 2.0×10⁻⁴, 5.6×10⁻⁴, and 6.8×10⁻⁴ S/cm, respectively. In the chloride and iodide compounds, the electronic contribution comprises approximately 1% of the total conductivity, although it exceeds 10% of the total conductivity in the bromide compound. Ag₆PSe₅Cl and Ag₆PSe₅Br exhibit purely Arrhenius behavior throughout the temperature range 150-300 K. Ag₆PSe₅I exhibits a second-order anomaly in electrical conductivity at 324 K.     

Electrical transport and crystallization in Cu+ ion substituted AgI–Ag2O–V2O5 glassy superionic system

A new glassy solid electrolyte system Cu_xAg_1 − xI–Ag₂O–V₂O₅ has been synthesized. The structural, thermal and electrical properties of the samples have been investigated. The glassy nature of the samples is confirmed by X-Ray diffraction and Differential Scanning Calorimetry studies. The electrical conductivity of these samples increases with CuI content and approaches a maximum value of ∼ 10⁻² Ω^− 1 cm^− 1 for x = 0.35 at room temperature. Ionic mobility measurements suggest that enhancement in the conductivity with Cu⁺ ion substitution may be attributed to increase in the mobility of Ag⁺ ions. The electrical conductivity versus temperature cycles carried out at well-controlled heating rate above T_g and T_c reveal interesting thermal properties. For lower CuI content samples conductivity exhibits anomalous rise above T_g and subsequent fall at T_c. It is also found that CuI addition into AgI–Ag₂O–V₂O₅ matrix reduces the extent of crystallization.     

Electrical,structural, magnetic and transport properties of Zn2BaFe16O27 doped with Cu

Series of polycrystalline samples of Zn_2−xCu_xBaFe₁₆O₂₇ were prepared by usual ceramic methods, where x=0.0, 0.4, 0.6, 0.8, 1.0, 1.4. X-ray analysis done at room temperature using CoK_α with λ=1.790 Å confirms the presence of W-type hexaferrite phase structure. Saturation magnetization and hysteresis loops curves measurements at room temperature were studied as a function of Cu²⁺ substitution. It can be seen that the Cu²⁺ content slightly decreases the saturation magnetization from 25 to 20 emu g⁻¹; all hysteresis loops are closed, which indicates low anisotropy field and low saturation magnetization field. The dc conductivity and thermoelectric power were measured in a range from room temperature up to T=750 K for all samples. The thermoelectric power decreases on increasing Cu²⁺ content, and the conductivity increases with temperature. The value of the charge-carrier concentration increases by increasing the temperature and Cu²⁺ content.     

Cu+ ion conductivity of K2Cu(CNS)3

K₂Cu(CNS)₃ is found to be a Cu⁺ ion conductor with a room temperature (30°C) conductivity of ～5×10^?3ω^?1 cm^?1. The phase structure of the CuCNS + KCNS system and data on temperature variation of the conductivity of K₂Cu(CNS)₃ is reported. The related compound KAg(CNS)₂ is found to be a Ag⁺ ion conductor.     

Electrical and optical absorption studies of Cu7GeS5I fast-ion conductor

Electrical conductivity and fundamental absorption spectra of monocrystalline Cu₇GeS₅I were measured in the temperature ranges 95-370 and 77-373 K, respectively. A rather high electrical conductivity (σ_t=6.98×10⁻³Ω⁻¹ cm⁻¹ at 300 K) and low activation energy (ΔE_a=0.183 eV) was found. The influence of different types of disordering on the Urbach absorption edge and electron-phonon interaction parameters were calculated, discussed and compared with the same parameters in Cu₇GeS₅I, Cu₆PX₅I (X=S,Se) and Ag₇GeX₅I (X=S,Se) compounds. We have concluded that the P→Ge and Cu→Ag cation substitution results in an increase of the electrical conductivity and a decrease of the activation energy. Besides, P→Ge substitution, results in complete smearing and disappearance of the exciton absorption bands and in blue shift of the Urbach absorption edge, an increase of the edge energy width and an electron-phonon-interaction enhancement.     

Structural,thermal and electrical properties of the semiconductor system Ag(1−x)CuxInSe2

This paper presents a study of bulk samples synthesized of the Ag_1−xCu_xInSe₂ semiconductor system. Structural, thermal and electrical properties, as a function of the nominal composition (Cu content) x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 were studied. The influence of x on parameters such as melting temperature, solid phase transition temperature, lattice parameters, bond lengths, crystallite size t (coherent domain), electrical resistivity, electrical mobility and majority carrier concentration was analyzed. The electrical parameters are analyzed at room temperature. In general, it is observed that the properties of the Ag_1−xCu_xInSe₂ system for x≤0.4 are dominated by n-AgInSe₂, while for x>0.4, these are in the domain of p-CuInSe₂. The crystallite size t in the whole composition range (x) is of the order of the nanoparticles. Secondary phases (CuSe, Ag₂Se and InSe) in small proportion were identified by XRD and DTA.     

Heat treatment effects in amorphous metals: Zr70Cu30 and La70Cu30

We measured the electrical resistivity (4–300 K), superconducting critical temperature and thermal conductivity (0.5–7 K) of the amorphous metals Zr₇₀Cu₃₀ and La₇₀Cu₃₀. Heat treatments below crystallization temperature induced changes in these properties. In particular, in the first stage of the annealing of Zr₇₀Cu₃₀ there are systematic changes in the thermal conductivity and the critical temperature, while the electrical resistivity remains constant. We show that there is no simple correlation between the thermal conductivity processes in the low temperature and plateau regions. We also show that the thermal conductivity of as quenched La₇₀Cu₃₀ is typical of amorphous metals, contrary to information previously reported.     

Structural and transport properties of CdI2 doped silver ion conducting system

The glass system xCdI₂-(100−x)[2Ag₂O-(0.7V₂O₅-0.3B₂O₃)] with different amount of dopant salt have been prepared by melt quenching technique. The sample obtained were pulverized and characterized by XRD, DSC, and FTIR. The electrical conductivity studies of the samples have been carried out at different temperatures and frequencies. Conductivity of the glasses increased with the increase in the CdI₂ contents and attains a value of 7.76×10⁻⁴ S/cm at room temperature for the composition having x=30 mol% of CdI₂. Infrared spectroscopic studies on these glasses indicated that the oxyanion network was not affected by the addition of CdI₂. The transport number of the silver ion determined by emf method is nearly unity. The frequency dependence of electrical conductivity for various glass compositions at different temperature has been analyzed in terms of Jonscher's Universal expression. In the present CdI₂ doped system, the conduction is due to the Ag⁺ ions attached to the AgI which is formed due to the exchange reaction between CdI₂ and Ag₂O.     

The thermoelectric power in AgxTiS2 and AgxNiPS3. Part II. The ionic component of the thermoelectric power

The EMF of the isothermal cells: Ag/AgI/Ag_xTiS₂: 0<x<1, T=150–200°C/Ag_xNiPS₃: 0<x<3, T=150–350°C has been measured. From the EMF-x curves the existence ranges of the 2-phase (stage I and II) regions ?0.16<x<0.32 for the Ag/Ag_xTiS₂ system at 190°C; 0.20 < x < 0.50 and 1 < x < 2 for the Ag/Ag_xNiPS₃ system at 400°C - have been determined. The results are sustained by X-ray diffraction and electrical conductivity measurements. From the EMF-T curves the partial enthalpy (ΔH?_Ag) and entropy (ΔS?_Ag) of dissolution of silver in the Ag_xSSE (solid solution electrode) materials were obtained. In the case of Ag_xTiS₂, ΔH?_Ag has a low absolute value, while ΔS?_Ag is distinctly positive. The EMF of the Ag/Ag_xNiPS₃ system also has a positive temperature coefficient. Furthermore, the ionic component of the thermoelectric power, ΔE/ΔT, of the thermogalvanic cells: Ag/AgI/Ag_xSSE/AgI/Ag Ag_xTiS₂: 0 < x < 1, T = 150–200°C( T ) (T+ΔT) Ag_xNiPS₃: 0 < x < 1, T= 150–350°C has been measured. The kinetically important heat of transport of silver ions in the Ag_xSSE materials has been determined in two ways: first from the dependence of the ionic Seebeck coefficient (?_Ag+) on reciprocal temperature; and second from direct calculation, using the data for ?_Ag+ and ΔS?_Ag. The heat of transport is much smaller than the activation enthalpy for Ag⁺-conduction, indicating a high ionic polaron binding energy in these materials.     

Optoelectronic properties of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite for p-type transparent conducting oxide

The samples of Cu_1−xPt_xFeO₂ (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity, hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08 Ω cm, 1.8 to 8.6 cm²/V s and 1.56 × 10¹⁸ to 4.04 × 10¹⁹ cm⁻³, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu_1−xPt_xFeO₂ delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity.     

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.     

Study of the CulCu2S system. conductivity of the solid solution Cu1+xI1−xSx(x<0.5)

A structural study of the CuICu₂S system has shown that a large solid solution ranges from pure CuI to Cu₃SI with a regular decrease of tehcell parameter ($\text{a=6.045 to 5.901}\text{A}\text{?}$); for richer Cu₂S concentrations, two-phase systems appear with the formation of a new Cu₇S₃I compound, and another solid solution exists for higher Cu₃S fractions (0.85<x<1). The ionic conductivity of the solid solution Cu_1+xI_1?xS_x (x<0.5) has been measured as a function of temperature between 54 and 307°C. The conductivity increases from 10^?7 ω^?1 cm^?1 (CuI) to 10^?3 ω^?1 cm^?1 (Cu_1.4I_0.6 S_0.4) at 25°C and then decreases until 10^?4 ω^?1 cm^?1 (Cu₃SI). In this last domain, no further phase transition occurs below the melting point and the low temperature γ phase can be considered as a stabilization of the high-conducting α phase. The variations of the conductivity are directly connected to those of the activation energy that decreases to a minimum value of 2.5 kcal mole^?1 for Cu_1.4I_0.6S_0.4.     

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.     

Large enhancement of room temperature magnetoresistance in Ag-added La0.67(Ca0.65Ba0.35)0.33MnO3

The electrical and magnetoresistant properties of La_0.67(Ca_0.65Ba_0.35)_0.33MnO₃/Ag_x (abbreviated by LCBMO/Ag_x) have been studied. The results show that Ag addition causes a decrease of resistivity dramatically and especially induces a large enhancement of room temperature magnetoresistance (MR). The room temperature MR ratio for x=0.27 sample in 10 kOe magnetic field is 41%, almost 20 times larger than that for x=0 sample. This enhancement is related to that the Curie temperature (T_c) of the sample is near room temperature, as well as the significant reduction of resistivity. The good fits of experimental results for x=0.27 sample to Brillouin function indicate that the MR behavior in the Ag added LCBMO is induced by the spin-dependent hopping of the electrons between the spin clusters, which is an intrinsic property of the CMR materials.     

Jahn-Teller transition in Al doped LiMn2O4 spinel

Al-doped lithium manganese spinels, with starting composition Li_1.02Al_xMn_1.98−xO₄ (0.00<x≤0.06), are investigated to determine the influence of the Al³⁺ doping on the Jahn-Teller (J-T) cooperative transition temperature T_J-T. X-ray powder diffraction (XRPD), nuclear magnetic resonance, electron paramagnetic resonance, conductivity and magnetic susceptibility data are put into relation with the tetrahedral and octahedral occupancy fraction of the spinel sites and with the homogeneous distribution of the Al³⁺ ions in the spinel phase. It is observed that Al³⁺ may distribute between the two cationic sublattices. The J-T distortion, associated with a drop of conductivity near room temperature in the undoped sample, is shifted towards lower temperature by very low substitution. However, for x>0.04 T_J-T it increases with increasing x, as clearly evidenced in low temperature XRPD observations. A charge distribution model in the cationic sublattice, for Al substitution, is proposed to explain this peculiar behavior.     

Electrical properties of MWCNT-composite (Se80Te20)100−xAgx (0 ≤ x ≤ 4) chalcogenide glasses

This article describes the preparation of multi-walled carbon nanotube (MWCNT) chalcogenide glass composite by the melt-quenching technique. MWCNT composite (Se₈₀Te₂₀)_100?xAg_x (0 ≤ x ≤ 4) bulk samples are characterized by the XRD, SEM and EDX. The electrical measurements were carried out in the temperature range of the 308-388 K. Cole–Cole plot has been used to determine the electrical conductivity at room temperature. It has been observed that MWCNT chalcogenide composite have higher value of electrical conductivity than pure glass. The results have been discussed on the basis of increased ionic conductivity (Ag⁺ ions) in MWCNT doped (Se₈₀Te₂₀)_100?xAg_x (0 ≤ x ≤ 4) bulk samples.     

Structural, ferroelectric and impedance spectroscopy properties of Y modified Pb(Fe0.5Nb0.5)O3 ceramics

Some ceramic samples of Pb_1−xY_x(Fe_0.5Nb_0.5)_1−x/4O₃ (PYFN) (0.00≤x≤0.08) were synthesized by a mixed oxide route. X-ray diffraction patterns of all the above samples confirm the formation of single phase material crystallizing in monoclinic structure. Dielectric properties (ε_r and tan δ) were analyzed in a wide temperature (30-350 °C) and frequency range (100 Hz-1 MHz). Ferroelectric properties of these compounds were confirmed from polarization (P-E hysteresis loop) measurements at room temperature. All the room temperature hysteresis loops of PYFN ceramics were well simulated using the ferroelectric capacitor model. Yttrium substitution resulted in notable enlargement of room temperature remnant polarization (2P_r). The 2P_r of PYFN (x=0.02) reaches to a large value (23 μC/cm²), which is nearly 5 times greater than that of PFN ceramic (4.6 μC/cm²). All the compounds exhibits negative temperature coefficient of resistivity (NTCR) type behavior as that of semiconductors. Dc conductivity (estimated via bulk resistivity) variation with temperature of all the samples follows Arrhenius type of electrical conductivity.     

Electrical conductivity of Ag/Na ion-exchanged titanosilicate glasses

The Ag₂O–TiO₂–SiO₂ glasses were prepared by Ag⁺/Na⁺ ion-exchange method from Na₂O–TiO₂–SiO₂ glasses at 380–450 °C below their glass transition temperatures (T_g), and their electrical conductivities were investigated as functions of TiO₂ content and the ion-exchange ratio (Ag/(Ag+Na)). In a series of glasses 20R₂O·xTiO₂·(80−x)SiO₂ with x=10, 20, 30 and 40 in mol%, the electrical conductivities at 200 °C of the fully ion-exchanged glasses of R=Ag were in the order of 10⁻⁵ or 10⁻⁴ S cm⁻¹ and were 1 or 2 orders of magnitude higher than those of the initial glasses of R=Na. The glass of x=30 exhibited the highest increase of conductivity from 3.8×10⁻⁷ to 1.3×10⁻⁴ S cm⁻¹ at 200 °C by Ag⁺/Na⁺ ion exchange among them. When the ion-exchange ratio was changed in 20R₂O·30TiO₂·50SiO₂ system, the electrical conductivity at 200 °C exhibited a minimum value of 7.6×10⁻⁸ S cm⁻¹ around Ag/(Ag+Na)=0.3 and increased steeply in the region of Ag/(Ag+Na)=0.5–1.0. When the ion-exchange temperature was changed from 450 to 400 °C, the conductivity of the ion-exchanged glass of x=30 decreased. The infrared spectroscopy measurement revealed that the ion-exchange temperature of 450 °C induced a structural change in the glass of x=30. The T_g of the fully ion-exchanged glass of x=30 was 498 °C. It was suggested that the incorporated silver ions changed the average coordination number of titanium ions to form higher ion-conducting pathway and resulted in high conductivity in the titanosilicate glasses.