Emf Measurements Research Articles

Proton conductivity of Ca-doped Ba2R1-xCaxNbO6-δ (R = La, Nd, Sm, Gd, Dy, Y, and Yb) ceramics with double perovskite structure

The influence of Ca substitution for R (R = La, Nd, Sm, Gd, Dy, Y, and Yb) on the electrical conductivity of double perovskite-structured Ba2R1-xCaxNbO6-δ (x = 0 and 0.2) ceramics was characterized in this study. Crystal structure analysis of Ba2R0.8Ca0.2NbO6-δ showed three types of lattices, monoclinic (R= La and Nd), tetragonal (R= Sm, Gd, and Dy) and cubic (R= Y and Yb), resulting the reduction of structural distortion for monoclinic structure by the Ca substitution for R. The significant differences in the electrical conductivity between the Ba2LaNbO6 and Ba2La0.8Ca0.2NbO6-δ ceramics may be related to the decrease in the structural distortion, as suggested by the changes in HT-XRPD patterns. Ba2La0.8Ca0.2NbO6 ceramic exhibited the highest electrical conductivity of 2.21 × 10−3 S/cm at 800 ℃ measured under a wet 1 % H2/Ar atmosphere. EMF measurements using a hydrogen concentration cell with water vapor and a water vapor concentration cell revealed that the predominant charge carriers in the Ba2R1-xCaxNbO6-δ ceramics were protons in the temperature range of 600–800 ℃.

Enthalpies of formation of RCoO3-δ (R = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y) perovskite cobaltites

Standard enthalpies of formation at 298.15 K, ΔfH298.15∘, for RCoO3-δ (R = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y) perovskite-type rare-earth cobaltites were obtained from the combined results of drop and reduction calorimetry. The relationship between the oxygen nonstoichiometry, δ, and thermodynamics of RCoO3-δ was discussed. The fact that RCoO3-δ with smaller ionic radius of R3+ tend to be less stable, having more positive enthalpy of formation from binary oxides (CoO and R2O3), Δf,oxH298.15∘, was confirmed for all the studied RCoO3-δ. Drop calorimetry results were also used in discussing, comparing and assessing the literature heat capacity, CpT, data for RCoO3-δ (R ≠ Y). For YCoO3-δ, both ΔfH298.15∘ and CpT were obtained for the first time solely from the drop calorimetric results; ΔfH298.15∘ values determined by two different methods perfectly agree with each other. The reference data and CpT of RCoO3-δ were used to calculate ΔfH298.15∘ from the published EMF measurement results so as to compare the available Δf,oxH298.15∘(RCoO3-δ) values. An unusual dependence of ΔfH298.15∘(LaCoO3-δ) on its heat treatment history was identified and supported by the additional isoperibolic solution calorimetry measurements.

Solid – phase equilibria and thermodynamic properties of the Sb-Te-S system

The powder X-ray diffraction (PXRD) analysis and the electromotive force (emf) measurements have been used to investigate the Sb–Te–S system in the Sb2S3-Sb2Te3-Te-S composition region at 300–450 K temperatures interval. Relative partial molar functions of antimony in alloys have been calculated and obtained data have been used to get self-consistent sets of the standard Gibbs free energy, standard enthalpy, and standard entropy of the Sb2S3 and Sb2Te2S compounds, as well as the Sb2Te2,4S0,6 and Sb2Te2,7S0,3 solid solutions. The data obtained for Sb2S3 have been compared to the ones available in the literature. Thermodynamic functions of the Sb2Te2S compound, as well as, the Sb2Te2,4S0,6 and Sb2Te2,7S0,3 solid solutions have been determined for the first time.

Measurement and Calibration of EMF: A Study Using Phone and GBDT for Mobile Communication Signals

AbstractElectromagnetic exposure caused by mobile communication signals has always been a cause of concern. Due to the cost and inconvenience of professional measurement equipment, researchers have turned to smartphone APPs to study and assess the electric field strength caused by mobile communication signals. However, existing cell phone‐based measurements have two weaknesses. First, no system architecture suitable for large‐scale crowdsourced testing has been proposed. Second, since smartphone sensors cannot measure electric field strength directly, existing methods for converting the received signal power of the phone and electric field strength have errors of more than 5 dB. This paper proposes a measurement and calibration method for electric field strength of mobile communication signals based on a smartphone app and gradient boosting decision tree (GBDT). This method consists of a downlink signal acquisition system based on an APP and a calibration model based on GBDT to convert received signal power into electric field strength. The experimental results show that the proposed model achieves a R2 score of 0.93 and a MAE of 0.97 dB. Compared with the existing methods, our method improves the calibration accuracy by 4 dB, enabling large‐scale, low‐cost, and high‐precision direct measurement of the electric field strength of mobile communication signals.

Metrological Support in the field of DC Voltage and EMF Measurements: from Normal Elements to a Quantum Standard

The article deals with the issues of metrological support on the example of the highest level of the State Verification Scheme for measuring instruments of direct current voltage and electromotive force. The origin and development of reference measurements of DC voltage and electromotive force in the Russian Empire, the USSR, and modern Russia is briefly reviewed. The results of work on improving the State Primary Standard GET 13 completed in 2022 are presented.

THERMODYNAMIC INVESTIGATION OF Ag8GeТe6 AND Ag8GeТe6-xSex SOLID SOLUTIONS BY THE EMF METHOD WITH A SOLID Ag+ Conducting Electrolyte

The thermodynamic properties of Ag8GeTe6 compound and Ag8GeТe6-xSex solid solutions were studied by EMF measurements of the concentration cells concerning to a silver electrode with Ag4RbI5 solid electrolyte in the 300–400 K temperature range. The partial thermodynamic functions of silver in alloys are calculated from the EMF measurements data. Based on the data on solid-phase equilibria in the Ag-Ge-Se-Te system, the potential-forming reactions responsible for these partial molar functions were determined and the standard thermodynamic functions of formation and standard entropies of the Ag8GeТe6 compound and solid solutions of the compositions Ag8GeTe5Se, Ag8GeTe4Se2, Ag8GeTe3Se3, Ag8GeTe2Se4 and Ag8GeTeSe5 were calculated.

THERMODYNAMIC PROPERTIES OF SOME TERNARY COMPOUNDS OF THE ARGYRODITE FAMILY

Compounds of the argyrodite family are valuable environmentally friendly functional materials with mixed ion-electronic conductivity, thermoelectric, photovoltaic, optical, and other properties. This paper presents the results of a thermodynamic study of the Cu8GeS6 and Cu8GeSe6 compounds - representatives of this family using the EMF method with Cu4RbCl3I2 solid electrolyte in the 295-430 K temperature range. From the EMF measurement data, the partial molar functions of copper were calculated in both crystal modifications of the Cu8GeS6 and Cu8GeSe6 compounds, undergoing polymorphic transformations at 330 and 335 K, respectively. Based on solid-phase equilibria diagrams of the Cu-Ge-S(Se) systems, the potential-forming reactions responsible for the partial molar functions of copper in the alloys were determined and the thermodynamic functions of formation and standard entropies of both modifications of these compounds, as well as the thermodynamic functions of their polymorphic transitions, were calculated. The work also presents and analyzes the thermodynamic data for compounds of the argyrodite family available in the literature

Thermodynamic properties of Nd-Fe alloys via emf measurements in LiCl-KCl-NdCl3 electrolyte

The thermodynamic properties of Nd-Fe alloys with varying mole fractions of Nd (xNd = 0.05–0.78) were investigated via electromotive force (emf) measurements in molten chloride at 773–1073 K. The Nd-Fe alloys were heat-treated at 923 K for 7 days to stabilize equilibrium phases, and the phase transition properties were confirmed by X-ray diffraction, electron microscopy, and differential scanning calorimetry. Employing less reactive Nd-Sn alloys (xNd = 0.10, L + NdSn3) as a reference electrode, the measured emf values were consistent between alloy compositions, as shown by equivalent thermal trajectories in distinct two-phase regions of [Fe + Nd2Fe17], [Nd2Fe17 + Nd5Fe17], [Nd5Fe17 + Nd], [L + Nd2Fe17], and [L + Nd5Fe17]. The measured emf results were further validated using open-circuit potentiometry in which Nd was deposited onto an Fe electrode at 973 K, resulting in a difference of less than 18 mV for the identical two-phase alloy between the two methods.

Strontium substituted sodium iron titanate as a possible sodium-ion conductor: Preliminary studies on preparation, crystalline transformation and conductivity

The rising interest in sodium-ion batteries is due to the widespread geographical availability of sodium and to qualify as a possible sodium-ion conductor, the proposed material should possess formidable structural stability and high ion conductivity. In the current work, therefore, the feasibility of employing strontium substituted sodium iron titanate (Sr-SIT) as a possible sodium-ion conductor was investigated. Synthesis of SIT and Sr exchange was accomplished through solution route. The crystalline transformation of Sr-SIT was elucidated through TG-DTA and XRD analyses in the temperature range of473 to 1273 K of calcination. Sodium-ion conductivity was established by EMF measurements.

(Invited) Thermodynamic Properties of Rare-Earth Alloys Relevant for Efficient Rare-Earth Recovery in Molten Salts

Electrode materials of Fe, liquid Bi, and Sn were investigated to enhance the electrochemical recovery of rare-earth elements in molten salts (eutectic LiCl-KCl) at 500‒700 °C, leveraging their chemical interactions with rare-earth elements. Using Nd as a prototypical example, the degree of interactions was quantified based on electromotive force (emf) measurements of Nd alloys (Nd-Fe, Nd-Bi, and Nd-Sn). Temperature-dependent emf values of the Nd alloys were used to determine the thermodynamic properties such as the partial molar Gibbs energy (chemical potential), entropy, and enthalpy of Nd. In addition, the phase behavior of Nd alloys was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) to determine transition temperatures and microstructures of Nd alloy electrodes. Based on these fundamental properties of Nd alloys, the Nd-Sn alloy at mole fraction, x Nd = 0.10 was selected as the reference electrode and employed for electrochemical measurements in three-electrode cells in molten chloride salt (LiCl-KCl-NdCl3). The stability of Nd-Sn reference electrode was maintained less than 1 mV deviation between identical constructs during entire measurements, originating from the two phase (liquid + NdSn3) stability of the binary Nd-Sn alloy at 500‒700 °C. Finally, electrodeposition of Nd onto these interacting electrode materials was conducted to assess the recovery efficiency of Nd from molten chloride salt.

Editors’ Choice—Equilibrium Boundaries of VO2 Phase Stability: Determination by Solid Electrolyte EMF Measurements and Effect on Optical Changes during Metal-Insulator Transition

Vanadium dioxide is widely known for its metal-insulator transition (MIT), in which drastic changes in resistivity and IR-transparency occur. This makes VO2 thin films promising materials for high-frequency optoelectronic devices. To get the most MIT sharpness, thin films should not contain impurities of hyper-oxygen or hypo-oxygen phases arising during VO2 synthesis. To ascertain the conditions of single-phase VO2 existence, the equilibrium boundaries of VO2 with neighboring phases were determined using the electromotive force method (EMF) with a solid electrolyte ZrO2(Y2O3). Our data for the high-oxygen boundary of VO2 existence in equilibrium with the V6O13 phase agree with the only data known in the literature. We established that VO2 is, in equilibrium with the V9O17 phase at the low-oxygen boundary, which forms V8O15 under further reduction. The temperature of the peritectoid decomposition of V9O17 is established, and the corresponding corrections to the phase diagram of the vanadium-oxygen system are introduced. The Gibbs energies for V9O17, V8O15, and V6O13 formation reactions are calculated. It is also shown that the IR reflectance of VO2 films brought to equilibrium at the high-oxygen boundary is much greater than that of films equilibrated at the low-oxygen boundary.

Fundamentals of liquid metal displacement reactions: Emf measurements of Na-Sn, Li-Sn, Mg-Sn, and Ca-Sn

The driving force of spontaneous displacement reactions between Na-Sn alloys and molten LiCl, MgCl2, and CaCl2 salts stems from the difference of chemical potential between Na and Li, Mg, or Ca in liquid Sn. However, fundamental thermodynamic data are absent. Herein, electromotive force (emf) values of Na-Sn, Li-Sn, Mg-Sn, and Ca-Sn alloys (electrodeposition of Na, Li, Mg, and Ca in liquid Sn via the coulometric titration) were measured in NaF-NaCl-NaI, LiF-LiCl, MgCl2-NaCl-KCl, and CaCl2-LiCl-NaCl salts respectively at 650 °C. The measured emf values of these alloys were normalized with respect to the Cl−/Cl2 potential that −3.14 V to −3.35 V for Na-Sn (mole fractions xNa = 0.02–0.30) alloy, −2.90 V to −3.21 V for Li-Sn (xLi = 0.02–0.30) alloy, −2.38 V to −2.45 V for Mg-Sn (xMg = 0.01–0.15) alloy, and −2.90 V to −3.06 V for Ca-Sn (xCa = 0.01–0.15) alloy. And Li20Sn, Mg10Sn, and Ca10Sn alloys were successful prepared by displacement reactions between Na20Sn alloys and LiCl-NaCl, MgCl2-NaCl, and CaCl2-NaCl salts, which offers theoretical guidelines for s-block elements extraction and separation.

Application of the Solute-Solvent EMF Cell to Measure Activity of NiF2 in Molten FLiNaK

Electromotive force (emf) measurements made using a combination of solute- and solvent-based electrodes were used to determine the activity of NiF2 in molten FLiNaK eutectic at 823 K across a concentration range of x NiF2 = 5.2 × 10–4–1.0 × 10–2. The solute emf values were measured using electrodes consisting of Ni wires immersed in FLiNaK with dissolved NiF2 contained in graphite crucibles. The measured emf values were then converted to the FLiNaK Eutectic Potassium Electrode (FEKE) potential and used to quantify the activity of dissolved NiF2. This quantification was based upon comparative measurements of a reference solvent electrode consisting of a K-Bi alloy immersed in pure FLiNaK contained in a boron nitride crucible and a solute electrode. Short cell lives were characteristic of the measurements due to the corrosive nature of the fluoride salts. Quantifying the activity of NiF2 will improve the utility of Ni2+/Ni reference electrodes in molten fluoride salts, which are notoriously difficult electrolytes to work with because of their reactivity. This work demonstrates the general nature of the solute-solvent approach as a repeatable, easily employed method for measuring the activity values of electroactive species in a variety of molten salts to improve understanding of the electroactive species behavior in these systems.

Cell voltage of mixed conductors under partially frozen conditions

Partially frozen-in states are rather the rule than the exception. Coexistence between equilibrium states and frozen-in states is relevant in view of the diversity and complexity of charge carriers, or sublattices, especially in multinary compounds, but also with respect to differently equilibrated spatial regions. This contribution deals with the open circuit potential of samples where only surface-near regions feel the outer partial pressure, or more generally, the component chemical potentials, established by the electrodes. In view of the significance of such measurements for separating ionic and electronic conductivity contributions, and the kinetic difficulties in getting full equilibration near room-temperature, the value of these considerations is obvious. The necessary relations are derived, or their derivations are sketched within the framework of linear force–flux laws. An account is made of recent emf measurements of hybrid halide perovskites, and a refinement of their standard defect diagram is recommended.

Thermodynamic functions of succinic acid in acetone–water binary mixtures based on computation of KI & KII constants

Succinic acid is commonly used in various chemical, pharmaceutical, environmental and industrial activities and its reactivity is principally determined by the pK(I & II) values. Therefore, the dissociation constants of succinic acid have been determined in this study on the basis of emf measurements in both different acetone mole fractions and temperature range. The pK(I or II) values of the studied acids in acetone aqueous media were found higher than those obtained in other organic aqueous media with the same conditions (temperature and mole fraction of solvent). Moreover, (KI/KII) in 40 wt% acetone–water mixture was identified to follow succinic acid < malic acid < malonic acid < maleic acid owing to the stabilization of intramolecular hydrogen bonding. The free energy of transfer (ΔG0I or II) for succinic acid was increased with the increasing of pKI or pKII values due to the decrease in relative permittivity (εr) via increment of the acetone fraction in the aqueous medium. The trend of ΔS°I value among the studied acids were found to follow maleic < malic < succinic < malonic. ΔS°II values were characterized lower than ΔS°I due to possible solvent interactions with the acid anion (L2-). Therefore, ΔH°II values of the second dissociation process were identified lower than ΔH°I to favor an exothermic reaction.

Gibbs Energy of Formation of U2Mo and U2Ti Determined by EMF Measurements in LiCl-KCl-UCl3 Melt

Gibbs energy of formation of U2Mo and U2Ti intermetallic phases in U-Mo and U-Ti binary systems, respectively was determined employing electromotive force measurements in LiCl-KCl-UCl3 melt. U-Mo and U-Ti alloys corresponding to two-phase field U2Mo+Mo and U2Ti+Ti were prepared by vacuum arc-melting and characterized by X-ray diffraction. Single phase U2Mo and U2Ti intermetallics were also prepared and characterized to support the indexing of Bragg peaks in two-phase alloys. Temperature dependence of ΔfGU2Mo∘ and ΔfGU2Ti∘ were, respectively expressed asΔfGU2Mo∘(kJ/mol-atom)=(−144.9±1.5)+(63±3)×10−3T(K)ΔfGU2Ti∘(kJ/mol-atom)=(−116.2±1.7)+(60±3)×10−3T(K)Since there were no other experimental data available that could be used to compare present correlations, results by DFT calculations from earlier works were compared and discussed. LiCl-KCl-UCl3 melt was analyzed after completion of electromotive force runs by cyclic voltammetry and no identifiable redox features due to Mo or Ti species in melt were observed. This suggested that both alloys remained stable in the melt even after 100 h duration of electromotive force runs and there was no chemical leaching of Mo or Ti from the alloy.

Relationship between low-frequency electromagnetic field and computer vision syndrome.

This study aimed to determine the prevalence of computer vision syndrome (CVS) among secretaries working in different departments of a university hospital in Turkey and its relationship with low-frequency electromagnetic field (LF-EMF) exposure. This cross-sectional study included 143 secretaries working in different departments of the hospital. Besides eye examinations, CVS Syndrome Questionnaire (CVS-Q) Scale and Ocular Surface Disease Index Scale (OSDI) were applied to the participants. LF-EMF of the work environment were measured with a 6010 Gauss/Teslameter device and the light intensity with an LX-1102 Device. The mean age of participants was 39.6 years, with a male-to-female ratio of 25.2% to 74.8%. CVS-Q scale revealed 83.9% of computer vision syndrome among participants. A weak positive correlation was found between CVS-Q and LF-EMF, while a moderately strong, negative correlation was found between LF-EMF and Schirmer test of both eyes. The work environment LF-EMF values were significantly higher among the participants diagnosed with CVS (p<0.05). The risk of CVS was found to increase 3.27 times when the ambient LF-EMF was >1,725 µT and an increase of 0.004 units in the CVS-Q score was calculated for each one-unit increase in the LF-EMF of the environment. A relationship between CVS, dry eye and EMF was observed among people exposed to LF-EMF. Regular measurement of EMF in work environments, and developing protective behaviours (work-break intervals, 20-20-20 rule, etc.) can be recommended.

Self-Sensing Six-Phase PMSM Drive Based on Back-EMF Measurement

This paper presents a novel procedure for the emergency sensorless operation of a six-phase electric drive. More degrees of freedom provided by multiphase technology have been utilized to determine the rotor flux position. The proposed technique is based on the direct measurement of the back EMF generated on a disconnected three-phase winding of a six-phase permanent-magnet synchronous machine (PMSM). The method is suitable for the emergency operation of an electric drive in the case of speed/position sensor failure. The proposed solution has been verified utilizing a six-phase permanent-magnet synchronous machine with a displacement of 30° between two three-phase sets of the stator winding and a power of 1 kW.

High Noon for Mobile Networks: Short-Time EMF Measurements to Capture Daily Exposure

High Noon for Mobile Networks: Short-Time EMF Measurements to Capture Daily Exposure

Back EMF Measurement Method and Consideration for Predicting Vibration of Brushed DC Motor

Back EMF Measurement Method and Consideration for Predicting Vibration of Brushed DC Motor