Activation Energy For Conduction Research Articles

Impedance spectroscopy and electrical conductivity of 0.7Bi(1−x)NdxFeO3–0.3BaTiO3 ferroelectric ceramics

0.7Bi[Formula: see text]NdxFeO3–0.3BaTiO3 (BNFO–BTO, [Formula: see text], 0.010, 0.020 and 0.050) ceramics were fabricated using the high-temperature solid-state reaction method. The X-ray diffraction (XRD) patterns revealed that the primary phase in these ceramics was pseudocubic. The Scanning Electron Microscopy (SEM) micrographs exhibited dense microstructures throughout all BNFO–BTO ceramics. Furthermore, the temperature dependence of dielectric behaviors and ferroelectric hysteresis loop shapes suggested the occurrence of a relaxor ferroelectric-type phase transition in BNFO–BTO ceramics. Additionally, the frequency dispersion characteristics and remnant polarization were enhanced with increasing substitution of Bi[Formula: see text] by Nd[Formula: see text]. Conducted impedance analysis on 0.7Bi[Formula: see text]NdxFeO3–0.3BaTiO3 ceramics and two dielectric responses of the grain at high frequency and grain boundary at low frequency were illustrated, respectively. The combination of imaginary impedance ([Formula: see text] and imaginary modulus ([Formula: see text] versus log[Formula: see text]f plots revealed that the charge carriers’ motion was not entirely long-range, short-range migration also exists. Through calculations based on Curie–Weiss Law, the relaxation activation energy ([Formula: see text] and conductance activation energy ([Formula: see text] were investigated, confirming that doping Nd[Formula: see text] effectively mitigates the concentration of oxygen vacancies (OVs) and prevents the formation of oxygen vacancies clusters, ultimately suppressing conductivity in BNFO–BTO ceramics.

Solid state synthesis of lead-free Sm-doped Na0.5Bi4.5Ti4O15 ceramics for enhanced dielectric and electrical properties

Here we report the synthesis of Sm-doped Na0.5Bi4.5Ti4O15 (Na0.5Sm0.5Bi4Ti4O15) lead-free ceramics via a conventional solid-state technique. Investigations of Na0.5Bi4.5Ti4O15 (NBT) and Na0.5Sm0.5Bi4.5Ti4O15 (NSBT) ceramics were demonstrated in detail to understand the composition-based structure-property of Aurivillius compounds and related functional material. Dielectric properties for frequency and temperature in a wide range were analyzed. The conduction activation energy values of NSBT ceramics are obtained to be 1.40 eV, whereas, the NBT ceramics get the value to be 1.31 eV. At higher temperatures, the conduction activation energy value of NSBT ceramics is 1.32 eV for both frequencies of 100 Hz and 1 kHz, whereas, for NBT compounds, the calculated value is 1.27 eV for both frequencies. The simulation performed on the impedance data for capacitive and resistance elements shows well-fitting curves which indicates a single relaxation behavior in the material. Similarly, the AC-conductivity data were analyzed which gives different conduction processes and relaxation activation energies in the NSBT ceramics.

Self-propagating room temperature synthesis of Ce0.8SmXM0.2-xO1.9(M= Gd, Nd, 0≤x≤0.2) co-doped ceria oxide-ion conductor ceramics for solid oxide fuel cells

Ce0.8SmXM0.2-xO1.9 (M = Gd, Nd, 0≤x ≤ 0.2) co-doped cerium oxide ionic conductor ceramics are prepared for the first time by a simple and time-saving self-propagating room temperature (SPRT) method. The uncalcined ceramic powders and the microstructure of the pellets sintered at 1400 °C are characterized by thermogravimetric analysis, Fourier-transformed infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. The density of the pellets is determined using the Archimedes method. The oxygen ion conductivity properties of the electrolytes are measured by electrochemical impedance spectroscopy. Impurity-free, non-porous electrolytes with high-density (>95 %) are successfully prepared. We report that the influence of dopant type and composition on the physical properties of the electrolytes prepared by the SPRT method is insignificant, with the total dopant concentration kept constant at 20 %. The dopant type and composition mainly influence the lattice parameters, grain interior conductivity of the grains, and the activation energy of the internal conductivity of the grains. Maximum oxygen ion conductivities are demonstrated with Ce0.8Sm0.1Nd0.1O1.9 and Ce0.8Sm0.15Gd0.05O1.9 samples for the Nd and Gd series, respectively. The highest ionic conductivity of 0.0677 S cm−1 and the lowest activation energy of 0.75 eV is achieved at a value of 10%Nd-10%Sm.

Effect of lattice defects on crystal structure and microwave properties of Ba(Ga1/2Ta1/2)O3 doped Ba(Zn1/3Nb2/3)O3 ceramics

Traditionally, B-site cation ordering structure in Ba(B′1/3B″2/3)O3 based ceramics with complex perovskite structure is considered to be the dominant factor in determining the dielectric loss. The crystal structure of BZN-BGT ceramics changes to the B-site disordering from B-site 1:2 ordering accompanying with remarkably reduced dielectric loss. Ba(Ga1/2Ta1/2)O3 doping also inhibits the formation of Nb-rich secondary phases induced by Zn volatilization on the surface of BZN-BGT ceramics as well. The conductive activation energy Ea, an energy required for electrons to escape from the traps, increases to 0.55 eV from 0.40 eV, indicating the decrease of lattice defects concentration. As Ba(Ga1/2Ta1/2)O3 doping concentration increases, the dielectric thermal relaxation process of BZN-BGT ceramics weakens and the electrical conductivity decreases. These results indicate that the dielectric loss of BZN-BGT ceramics containing volatile Zn could be controlled by the lattice defects and secondary phases rather than B-site 1:2 ordering structure.

Localized high concentration polymer electrolyte enabling room temperature solid-state lithium metal batteries with stable LiF-rich interphases

Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) based polymer electrolyte shows mechanical flexibility, soft and intimidate physical contact and good electrochemical stability, however, low ionic conductivity at room temperature and unstable interphases against Li metal hinder its application. In this article, we propose a universal strategy to prepare localized high concentration polymer electrolytes (LHCPE) in which high concentration lithium salt (LiTFSI) dissolved in tiny residual solvent (DMF) and the PVDF-HFP serves as solid dilution. The LHCPE regulates the solvation structure of lithium ions with anions instead of DMF solvent, allowing more anions to coordinate with Li+ and forming amount contact ion pairs (CIPs) and aggregates (AGGs). As a result, high ionic conductivity (5.9 × 10−4 S cm−1) and low activation energy (0.10 eV) achieved. The LHCPE also induces the decomposition of anions-derived LiF-rich interphases, that is ionic conducive and mechanical robust, thereby greatly improving the charge transfer kinetics and stability towards Li metal anodes. Consequently, at 0.5 mA cm−2 and 0.25 mAh cm−2, stable and long-term cycling over 2000 h obtained under room temperature in Li//Li symmetric cells achieved. The full solid-state LFP//LHCPE//Li cells further exhibit excellent capacity retention of 82.83 % even after 1200 cycles at room temperature and a high rate of 8 C (1C=170 mA·g−1). Our work shed light on the design of high-performance polymer-based composite electrolytes by manipulating the Li solvation structure.

Impact on activation energy with elevating calcination temperature of barium bismuth ferrite nanocomposite

Barium Bismuth Ferrite nanoparticles having the general formula Ba1-xBixFeO3 were successfully made by the sol-gel system, using nitrates as the fundamental material. Tartaric acid and polyvinyl alcohol were used as chelating agents. The synthesized nanoparticle powder was sintered at 650 ̊C and 750 ̊C for 3 h. Filtering with dilute nitric acid and distilled water is used to remove the impurities. The structural, optical, and dielectric properties were determined at room temperature. Using X-ray diffraction (XRD) analysis, structure, lattice parameter, microstrain, and dislocation density were calculated. Using the Scherrer equation, the peak's crystalline size was ascertained. In FTIR, the vibrational modes of the octahedral and tetrahedral metal complexes in the sample have been studied using the wavenumber in this range. The synthesized nanocomposite contains morphological features, such as interconnecting agglomerates with spherical, irregular, or non-uniform elongated shapes, as demonstrated by SEM images. The activation energy for relaxation and activation energy for conduction was measured from the Cole-Cole plot and the AC conductivity versus frequency plot respectively. The determined activation energies from the two investigations were relatively close to one another. The Barium Bismuth Ferrite nanoparticles samples at room temperature indicate that the samples have implicit candidates for information storage devices for spintronic devices. In the high frequency range, all samples depending upon the temperature demonstrate excellent dielectric behaviour and small dielectric loss, and with stable dielectric constant, these samples make their prospective for the practical application in spintronic devices the main goal of this work.

Evolution of the Electrical Conductivity of LiNb1−xTaxO3 Solid Solutions across the Ferroelectric Phase Transformation

The investigation of the structural phase transition in the vicinity of the Curie temperature of crystals is motivated by the expected combination of advantageous high‐temperature properties of and , including high piezoelectric modules and remarkable high‐temperature stability, respectively. marks the ultimate limit for exploiting the piezoelectric properties; however, transition‐related structural modifications might impact this and other properties even below . Remarkably, the phase transition from the ferroelectric to the paraelectric phase, whose temperature strongly depends on the composition x, shows a significant drop in the activation energy of the electrical conductivity. The magnitude, temperature dependence, and underlying mechanisms of this drop are discussed from a microscopic perspective. Molecular dynamics calculations in the framework of the density functional theory show that substantial displacements of the cations occur below for both the end compounds and , and might thus affect the electrical conductivity. Above , the migration of lithium ions is presumably facilitated by a shortened diffusion path for the most favorable jump of the lithium ions. Electronic contributions to the conductivity, which become important above 900 K, are explained within the polaronic picture by the formation and migration of free small polarons.

Anisotropic polyphenylene-based anion-exchange membranes with flexible side-chains via click reaction for high-performance water electrolysis

Anion-exchange membrane water electrolysis (AEMWE) represents a promising and cost-effective electrochemical energy conversion system for green hydrogen production owing to its utilization of earth-abundant metals for various cell components (catalysts, porous transport layers, bipolar plates) and the zero-gap design. However, the lack of high-performance anion-exchange membranes (AEMs) has hampered the advancement of AEMWE technology. Here, by using colon coupling and click reactions, the ether-free polyphenylene-based AEMs (QPPBTF-TMA-w) with flexible side-chains containing triazole linkers. The QPPBTF-TMA-w membranes stand out for their lower activation energy for hydroxide conduction which is attributed to the well-structured ion-conducting channels via distinct phase separation facilitated by the triazole linker, which optimizes hydrophilicity and ensures efficient ion transport within the membrane. In addition, the QPPBTF-TMA-w membranes exhibit unique anisotropic swelling and ion-conduction behaviors, such as lower in-plane swelling and higher through-plane conductivity, which are advantageous for practical cell applications. Therefore, despite having a modest ion exchange capacity (IEC) value of 2.0, the QPPBTF-TMA-w membrane delivers high-performance in anion-exchange membrane water electrolysis (AEMWE), achieving 6.4 A/cm2 at 2.0 V at 70 °C using a 1.0 M KOH solution.

Effect of A/B ratio on the dielectric properties and insulation resistance of barium titanate sintered in a reducing atmosphere

The effect of the A/B ratio on the dielectric properties and insulation resistance of barium titanate (BaTiO3) sintered in a reducing atmosphere was investigated in this study. The increased demand for high capacitance, miniaturized, and reliable base metal electrode multilayer ceramic capacitors (BME MLCCs) has emphasized improving insulation properties. This study added Y2O3, MgO, Mn2O3, and SiO2 to tailor the barium titanate properties. We investigated how changes in the A/B ratio affect the microstructure, defect chemistry, and Y3+ ion occupation in BaTiO3, affecting dielectric properties and insulation resistance. It was observed that the activation energies for grain and grain boundary conductivity are dominated by oxygen vacancy and (VBa″−VO··) defect pair, respectively. The Ti3+ and oxygen vacancy concentrations were directly proportional to the room and high-temperature resistivities, respectively. The sample with an A/B ratio of 1.002 had the lowest oxygen vacancy and Ti3+ ratio, resulting in a higher resistance and lower thermally stimulated depolarization current (TSDC).

Structure and Properties of Na2S-SiS2-P2S5-NaPO3 Glassy Solid Electrolytes.

In the development of sodium all-solid-state batteries (ASSBs), research efforts have focused on synthesizing highly conducting and electrochemically stable solid-state electrolytes. Glassy solid electrolytes (GSEs) have been considered very promising due to their tunable chemistry and resistance to dendrite growth. For these reasons, we focus here on the atomic-level structures and properties of GSEs in the compositional series (0.6-0.08y)Na2S + (0.4 + 0.08y)[(1 - y)[(1 - x)SiS2 + xPS5/2] + yNaPO3] (NaPSiSO). The mechanical moduli, glass transition temperatures, and temperature-dependent conductivity were determined and related to their short-range order structures that were determined using Raman, Fourier transform infrared, and 31P and 29Si magic angle spinning nuclear magnetic resonance spectroscopies. In addition, the conductivity activation energies were modeled using the Christensen-Martin-Anderson-Stuart model. These GSEs appear to be highly crystallization-resistant in the supercooled liquid region where no measurable crystallization below 450 °C could be observed in differential scanning calorimetry studies. Additionally, these GSEs were found to be highly conducting, with conductivities on the order of 10-5 (Ω cm)-1 at room temperature, and processable in the supercooled state without crystallization. For all these reasons, these NaPSiSO GSEs are considered to be highly competitive and easily processable candidate GSEs for enabling sodium ASSBs.

Effects of Fe2+ on dielectric and magnetic properties in rare earth garnet type high entropy oxides

Given the important role played by the valence state of the transition metal in determining material this paper investigates the effect of Fe2+ content on the structure and dielectric properties of garnet-structured high entropy oxides (Y0.2Eu0.2Er0.2Dy0.2Lu0.2)3(Al0·5Fe0.5)5O12 through Fe2+ doping. The results of XPS and Mӧssbauer spectra showed that the Fe2+ content in the tetrahedron increased with Fe2+ doping. With increasing Fe2+ content, the dielectric constants gradually increased, and the maximum dielectric constant reached 2.78 × 104 at 100 Hz under 30 °C. The analysis of the AC impedance spectrum and electrical conductivity revealed that the difference between the activation energy of grain boundary and grain conductivity resulted in increased dielectric constants of the samples. In addition, the doping of Fe2+ increased the maximum magnetization of the samples. This work provides a new idea for designing giant dielectric materials and magnetic materials with a high entropy strategy.

Structural, optical, and electrical characterization of TiO2-doped yttria-stabilized zirconia electrolytes grown by atomic layer deposition

Electrolyte material optimization is crucial for electrochemical energy storage devices. The specific composition and structure have an impact on conductivity and stability, both of which are essential for efficient device performance. The effects of controlled incorporation of TiO2 into a Yttria-Stabilized Zirconia (YSZ) electrolyte using the atomic layer deposition (ALD) technique are investigated in this study. The surface chemical composition analysis reveals variations in the Ti oxidation state and a decrease in the O/(Zr + Y + Ti) ratio as TiO2 concentration increases. The formation of acceptor states near the valence band is proposed to reduce the bandgap with the Fermi level. The structural properties indicate that as TiO2 concentration increases, surface homogeneity and crystallite size increase. The contact angle with water indicates a hydrophobic behavior influenced by surface morphology and potential oxygen vacancies. Finally, electrical properties, measured in Ru/TiO2-doped YSZ/Au capacitors operated at temperatures between 100 and 170 °C, showed that the TiO2 incorporation improved the ionic conductivity, decreased the activation energy for conductivity, and improved the capacitance of the cells. This study highlights the importance of the ALD technique in solid-state electrolyte engineering for specific applications, such as energy storage devices.

DISCUSSION OF THE MECHANISM OF THE ELECTRICAL CONDUCTIVITY OF PURE WATER IN THE FRAMEWORK OF THE BJERRUM MODEL

An alternative mechanism of electrical conductivity and ionization of molecules in pure water is considered. Calculation of the temperature dependence for the activation energy of ionization of water molecules was carried out using data on the value of its ionic product. The calculated activation energies for the ionization and flow processes show the presence of a certain proportionality between them. This suggests that the ionization of water is caused by intermolecular forces rather than intramolecular forces. Accordingly, the electrical conductivity of water is associated with the appearance and movement in it of L and D defects of hydrogen bonds between water molecules, which have significant electrical pseudo charges and are considered in the Bjerrum model for ice. This work proposes a new interpretation of the mechanism of ionization (pseudoionization) of molecules and generation of L and D defects in water. Rotation is considered not for one, but for two of its molecules in opposite directions with partial compensation of their angular momentum, and the breaking of not three bonds for one molecule, but four bonds with neighbors for two molecules. Moreover, these four neighbors do not include molecules from water clusters that have stronger bonds, since neighboring molecules with weaker bonds can be found for the process of rotation activation. Accordingly, the exponential contribution made by molecules from water clusters is absent or small in the ionization activation energy. In this way, the activation energy for the flow, which occurs throughout the entire volume of the liquid and automatically includes molecules from clusters, differs from the activation energy of electrical conductivity, which occurs for individual molecules in chains of bonds. The presence of a maximum in the ionic product of water near 250 ⁰C can be explained by the rapid decrease in the lifetime of L and D defects with heating, which prevents the use of the standard equation for accurate calculation of the ionization activation energy above 100...200 ⁰C. However, the presence of this maximum contradicts the generally accepted model of proton hopping between neighboring hydronium and water molecules in the mechanism of its electrical conductivity.

ОЦІНКА СТРУКТУРИ ШЛАКОВИХ РОЗПЛАВІВ НА ПІДСТАВІ АНАЛІЗУ ТЕМПЕРАТУРНИХ ЗАЛЕЖНОСТЕЙ В’ЯЗКОСТІ ТА ЕЛЕКТРОПРОВІДНОСТІ З ВИКОРИСТАННЯМ АДАПТИВНОЇ СЕГМЕНТНОЇ РЕГРЕСІЙНОЇ МОДЕЛІ

The expediency of using an adaptive segmented regression model for the analysis of logarithmic dependences of viscosity and electrical conductivity on temperature to assess the structure of slag melts is shown. Calculated values of the activation energies of viscosity ( ) and electrical conductivity ( ) in different temperature ranges. The obtained calculation results confirm that the viscosity and electrical conductivity of slag melts characterize the interaction of various structural particles (ions and/or their groups) and can be used in the study of the structure of slag melts. It was established that the activation energy of viscosity and electrical conductivity decreases as the temperature of slag melts increases. The performed calculations of the indicator n=En/Ex indicate that it can be a criterion for evaluating the structure of the slag melt, when n >1, the slag melt is a heterogeneous system, and when n < 1, it is a homogeneous system. Viscosity and electrical conductivity are interdependent properties and can be predicted if there is data on one of the properties, provided the value of n is known.

Study of Conduction Mechanisms in Alkali and Transition Metal Oxides Doped Borosilicate Glasses

Objectives: To synthesise a unique set of borosilicate glasses of composition, xLi2O + 0.15SiO2 + 0.45B2O3 + 0.05ZnO + (0.35 – x) WO3; (0.25 ≤ x ≤ 0.34) and to investigate conduction mechanisms. Methods: Glasses were synthesized by melt quenching technique. From the XRD spectra samples were conformed to be non-crystalline in nature. Density has been measured by following Archimedes principle and is found to decrease with Li2O mole fractions in the range 2.900 gm/cm3 – 2.495 gm/cm3. DC-conductivity was measured for the temperature range 303K – 525 K using two probe technique. Findings: It was found that these glasses behave like semiconductors in terms conductivity variation with temperature. Conductivity decreased with Li2O content up to 0.33 mole fractions and increases for higher mole fractions. High temperature conductivity variation i.e., above ϴD/2 (ϴD = Debye’s temperature) is found to follow the Mott’s small polaron hopping (SPH) model. Activation energy for conduction above ϴD/2 is found to be in the range 0.282 eV-0.702 eV. Decrease of conductivity and activation energy with increase of Li2O content has been explained in terms of dynamic nature of network and formation of cation-polaron neutral entities. The conductivity below ϴD/2 has been found to follow Mott’s variable range hopping (VRH) models. The density of states at Fermi level derived from Mott’s VRH are found to be of the order of 1023 eV-1cm-3 which are in close agreement with reported ranges for transition metal oxides doped glasses. Novelty: A unique set of mixed conducting borosilicate glasses have been prepared and investigated thoroughly for conduction mechanisms. Keywords: Borosilicate glasses, Density, Conductivity, Activation energy, Density of states

Effect of background gas composition on the stoichiometry and lithium ion conductivity of pulse laser deposited epitaxial lithium lanthanum tantalate (Li3xLa1/3−xTaO3)

Lithium lanthanum tantalate (Li3xLa1/3−xTaO3, x = 0.075) thin films were grown via pulsed laser deposition using background gas atmospheres with varying partial pressures of oxygen and argon. The background gas composition was varied from 100% to 6.6% oxygen, with the pressure fixed at 150 mTorr. The maximum ion conductivity of 1.5 × 10−6 S/cm was found for the film deposited in 100% oxygen. The ion conductivity of the films was found to decrease with reduced oxygen content from 100% to 16.6% O2 in the background gas. The 6.6% oxygen background condition produced ion conductivity that approached that of the 100% oxygen condition film. The lithium transfer from the target to the film was found to decrease monotonically with decreasing oxygen content in the background gas but did not account for all changes in the ion conductivity. The activation energy of ion conduction was measured and found to correlate well with the measured ion conductivity trends. Analysis of x-ray diffraction results revealed that the films also exhibited a change in the lattice parameter that directly correlated with the ion conduction activation energy, indicating that a primary factor for determining the conductivity of these films is the changing size of the ion conduction bottleneck, which controls the activation energy of ion conduction.

Strongly correlated electron system NiWO4: A new family of materials for triboelectrics using inherent Coulombic repulsion

The strongly correlated electron system (SCES) insulators promise a wide range of intriguing physical phenomena arising from the exotic charge gap depending on the strength of the Coulombic repulsion between d and f orbital cations. The SCES exhibits polaron hopping conduction, which requires a higher activation energy for carrier conduction between nearest cations, indicating a strong insulating character with relatively high permittivity. Here, we demonstrate that the NiWO4 SCES insulator, which is formed by Coulombic repulsion between the nearest d orbital of Ni, proposes a suitable triboelectric material unlisted system from conventional metal oxides. The higher degree of freedom in NiWO4 by the lower symmetry of monoclinic structure and an additional selection of composition exhibits high relative permittivity (∼13.8) in a wide range of temperatures (up to 180 ℃). The optimized simple mixture of NiWO4 and PDMS (polydimethylsiloxane) for the negatively charged material to triboelectric nanogenerator (TENG) presents 1.78 times higher output compared to the pristine PDMS film-based TENG. NiWO4, considering the physical properties of the SCES determined by Coulombic repulsion strength, paves the way for a new option of TENG materials following the high permittivity.

Dielectric relaxation studies in Sm2O3 doped boro-zinc-vanadate glasses

In this work, the conventional melting procedure was adopted to synthesize glasses with a composition of (ZnO)0.3 – (V2O5)0.3 – (B2O3)0.4-x – (Sm2O3)x, x = 0.002, 0.005, 0.007, 0.01 and 0.02 mol%. The dielectric properties of these glasses were measured. The dielectric constant (εʹ) and dielectric loss (εʹʹ) of glasses are found to vary in the range from 1.9177x102 to 3.9456x103 and from 1.5751 to 6.9095x105 respectively for the temperature range 343 K – 573 K and frequency range 50 Hz to 10 MHz. With increase of frequency, both dielectric constant and loss decreased and increased with increase of temperature. The analysis of dielectric constant and dielectric loss confirmed that the phenomenon of dielectric relaxation is mainly due to the frequency-dependent polarization mechanism. Electric modulus and impedence spectroscopy revealed non-Debye type and a single phase relaxation process. Activation energy for dc conductivity and dielectric relaxation are found to be of same size indicating that the potential barrier encountered by the charge carriers is same in both the processes. The master curves suggested that temperature-independent relaxation is occurring in the present glasses. The high values of measured dielectric parameters suggest that the present glasses are suitable in semiconducting and energy storage applications.

Structural and dielectric properties of CaSnO3-doped Sr2.1Na0.8Nb5O15 ceramics

The crystallographic, microstructural, and dielectric properties of Sr2.1Na0.8-xCaxNb5-xSnxO15 (x = 0.00, 0.01, 0.05, 0.10) polycrystalline ceramics have been studied by X-ray diffraction, scanning electron microscopy, dielectric spectroscopy (DS) and impedance spectroscopy (IS). For x = 0.00, 0.05, and 0.10, samples are single phase with P4bm symmetry at room temperature with x = 0.01 showing a small quantity of secondary phase(s). All compositions show typical ceramic microstructures and d50 grain sizes ranging from 5.1 to 26.6 μm. DS shows a clear trend in the high temperature ferroelectric-paraelectric transition with the Curie temperature, T0, decreasing from ∼ 160 to ∼ 110 °C, and an additional relaxation at approximately 120 °C with increasing CaSnO3. IS reveals all samples have a homogeneous electrical microstructure with predominantly electronic conduction. The activation energy of conduction calculated from Arrhenius plots of the conductivity increases with CaSnO3 content from 1.27 to 1.38 eV likely due to the expansion of the band gap.

Electrical characterization of interfacial transition zone in concrete during freeze-thaw process

The interfacial transition zones (ITZs) between aggregates and mortar are weak regions of concrete, which are more critical to the frost resistance of concrete due to a larger localized water-to-cement ratio. The effective conductivity of the ITZ was determined by separating electrical parameters in the AC impedance spectrum (ACIS), and the changes in microstructure within ITZ during the freeze-thaw (F-T) process were studied. First, based on the microstructure characteristics of Cement-Based Materials (CBMs), a circuit model of conduction path of conductive unit was established. The microstructure changes of CBMs during the F-T process (−50 °C to 10 °C) were characterized using ion conduction activation energy and the impedance of the constant phase element (CPE), which were classified into different regions in the F-T process. Circuit simplification and impedance parameters of CPE in different regions were analyzed. Subsequently, the composite effective conductivity formula (CECF) was proposed to separate the ITZ conductivity from the mortar or concrete conductivity. The relative change rate of conductivity during F-T process was used to define the freezing degree of CBMs, and the freezing degree of ITZ was calculated by CECF. The results indicated that in the F-T process of mortar and concrete, despite the volume fractions of ITZ being only 15.8% and 10.6%, its contribution to the freezing degree of the overall sample was 66%−70% and 57%−60%, respectively. This method can quantitatively characterize the effect of ITZ during F-T process and help understand the damage mechanism of F-T process.