Activation Energy For Conduction Research Articles

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.

Self-assembled Gd0.1Ce0.9O1.95-BaGd0.8La0.2Co2O6‒δ nanocomposite cathode for efficient protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs) are characterized by a low activation energy for proton conduction and a high fuel utilization efficiency at low-to-intermediate temperatures. However, the sluggish oxygen reduction reaction kinetics on the cathodes drastically limit the power output performance of PCFCs. Herein, multiphase Gd0.1Ce0.9O1.95-BaGd0.8La0.2Co2O6‒δ (GDC-BGLC) nanocomposite cathodes are prepared by coupling self-assembly and sintering-free electrode construction methods. The nanocomposite cathode comprises mixed H+/e– conducting BGLC and O2− conducting GDC and BaCoO3 nanoparticles, and these phases are homogeneously mixed with coherent heterointerfaces. The nanocomposite cathode exhibits a significant increase in surface oxygen vacancies and three-phase boundaries, enhanced catalytic activity, and reduced activation energy for the oxygen reduction and water formation reactions. The results imply that the oxygen reduction and water formation reactions on the multiphase GDC-BGLC nanocomposite electrodes are most likely the dissociation, reduction and diffusion of oxygen species, which in turn is affected by the water vapor formed. An anode-supported single cell with the GDC-BGLC cathode exhibits a peak power density of 810 mW cm−2 at 700 °C with excellent operating stability at 650 °C for 110 h. This study provides a new strategy for the preparation of a high-performance and durable nanocomposite cathode for PCFCs.

A comprehensive study of dielectric, modulus, impedance, and conductivity of SrCeO3 synthesized by the combustion method

AbstractIn this work, perovskite oxide SrCeO3 was synthesized using the solution combustion method (SCM). Synthesized samples have been characterized using X‐ray diffraction (XRD), Raman, ultra violet (UV)–visible spectroscopy, and scanning electron microscopy (SEM) techniques. The XRD and Rietveld refinement has confirmed the orthorhombic structure with space group Pnma. The average grain size of this ceramic sample is 1.2 µm. The dielectric constant, dissipation factor, modulus, impedance, and alternating current (AC) and direct current (DC) conductivities were analyzed in the temperature range RT to 600°C and frequency range 20 Hz–2 MHz. Further, it was observed that the role of grain boundaries in dielectric and electrical properties is significant, at low temperatures. The origin of the dielectric relaxation and conduction process is the same. The activation energy for DC conduction (Edc) was found to be .79 eV. Electrical conduction/relaxation is assigned to the diffusion of doubly ionized oxygen (Vo··). The value of DC conductivity (1.2 × 10−3 Ω−1 cm−1 at 600°C) and activation energy of .79 eV is very close to the values reported for doped CeO2‐based oxide ion conductors for SOFCs. This study has demonstrated that SrCeO3 can be an alternative candidate for the oxide ion conductor electrolyte application and the potential to be used as a thermally stable capacitor application for microwave dielectric applications.

Electrical properties of A-site Ca-doped LaNb1-xAsxO4-δ ceramics

The electrical properties of A-site Ca-doped LaNbO4 with the addition of As in the B-site, have been investigated. Total, grain- and specific grain boundary electric conductivities in different oxygen partial pressure, and water vapour partial pressure were determined. Additional conductivity measurements were performed in nitrogen, to suppress the possible p-type conductivity, focusing on protonic conductivity. The maximum measured total conductivity was recorded for La0.99Ca0.01Nb0.9As0.1O4-δ at 800 °C, which was equal to 1.2·10−4 S·cm−1 in H2O- humidified air, and 2.2·10−5 S·cm−1 in H2O- humidified N2. From the deconvoluted data, the lowest activation energies for grain conduction were obtained in both atmospheres for La0.99Ca0.01Nb0.7As0.3O4-δ. In the temperature range 400 °C – 550 °C it was 0.23 eV and 0.13 eV respectively for H2O- humidified air and H2O- humidified N2. The results show that the increasing arsenic amount mainly influences the activation energies, whereas the calcium addition slightly improves the grain conductivity. The pO2 experiments revealed that in oxidizing atmospheres, electron holes contribute to the conductivity. The high proton transfer numbers were obtained for each sample, peaking at tH+ = 0.91 for LaNb0.7As0.3O4 at 400 °C. Interestingly, even at elevated temperatures relatively high values are obtained where tH+ = 0.87 was recorded at 800 °C for La0.99Ca0.01Nb0.9As0.1O4-δ.

Dielectric and viscoelastic properties of 3D-printed biobased materials

This study aimed to develop new biobased materials containing plasticized cellulose acetate (CA) by Fused Filament Fabrication (FFF). We investigated the influence of CA on the viscoelastic/dielectric properties and the influence of 3D printing on the dielectric properties of the polymer blends. A microstructural analysis showed that the blends had a strong heterogeneous morphology, as the two phases formed a fibrillar and lamellar structure. CA strongly increased the blend viscosity at 175 °C, multiplying by 100 times the complex viscosity between neat PLA and the blend containing 40% of CA by weight (CA-40). The addition of CA to the blends increased the dielectric constant (ε') and dielectric loss (ε''), as well as the alternative current electrical conductivity (σAC). The dielectric constant of CA (ε'CA) was proportional to its percentage in the blend, showing a behavior analogous to a rule of mixture. Moreover, the activation energy of the electrical conductivity (σDC) measured at T > 124 °C decreased with increasing CA content and was associated with the enhancement of the ionic conductivity provided by the CA and its plasticizer. A decrease in the α-relaxation temperature and the associated activation energy of the PLA was also linked to the presence of the CA plasticizer. Finally, 3D printing greatly decreased both ε', ε'' and σAC due to the internal voids induced by the 3D printing process. The porosity was measured at 12% for neat PLA and between 20% and 25% for the blends. These results showed the advantage provided by FFF technology in the production of PLA:CA blends with controlled dielectric properties, thereby favoring the use of these new materials in key dielectric areas.

Facile one-step preparation of Co2CrO4 spinel from heterometallic compounds – Structural, magnetic, electrical and photocatalytic studies

Two isostructural heterometallic complex salts with mononuclear units, [NH(CH3)2(C2H5)][Cr(terpy)2][CoCl4]2 (1) and [NH(CH3)(C2H5)2][Cr(terpy)2][CoCl4]2 (2), were synthesized using a building block approach and characterized by single-crystal and powder X-ray diffraction (XRD), impedance spectroscopy and magnetization measurements. They exhibit particular humidity-sensing properties and very high proton conductivity at room temperature. The magnetization of complexes shows the high spin state of 3/2 for tetrahedrally coordinated CoII ions, which on cooling remain in the paramagnetic state within the CrIII network, which is antiferromagnetically correlated. The prepared compounds were thoroughly explored as single-source precursors for the formation of the spinel oxide Co2CrO4 by their thermal decomposition. By optimizing the annealing temperature, heating/cooling rates and holding times, the phase composition of thermal processing of 1 or 2 was evaluated: phase pure spinel Co2CrO4 was obtained by thermal treatment already at 450 °C. The structure, morphology, and optical properties of spinel oxides prepared at different temperatures were characterized using powder XRD, field emission scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), while electrical and magnetic by impedance spectroscopy and magnetization measurements. The determined band gap energy and nanosized crystallites prompted us to investigate the photocatalytic activity of spinel oxide produced at 450 °C in the degradation of dyes Rhodamine B (RhB) and Methylene blue (MB) under Vis irradiation without and with assistance of hydrogen peroxide (H2O2). The results show that the Co2CrO4/H2O2 system exhibits a significantly higher photoactivity response; the degradation efficiency of MB and RhB was found to be 86.1% and 80.3%, respectively. The electrical conductivity spectra and the activation energy for the DC conductivity demonstrate the electronically semiconducting behaviour of the Co2CrO4 oxide. The Co2CrO4 spinel has a ferrimagnetic ground state, with mixed CoII and CoIII ions on the tetrahedral and octahedral sites: CoII having a high spin state on both sites and CoIII having a high spin state on the tetrahedral site and a low spin state on the octahedral site. Different thermal treatments affect the magnetization according to the different sizes of the obtained crystallites.

Enhanced structural, electrical, and electrochemical performance of polyethylene oxides (PEO)‐based polymer electrolytes for solid state K+ ion batteries

AbstractFlexible polymer electrolytes with effective electrochemical characteristics must be developed to meet smart electronic technology demands. The current investigation explores the solid polymer electrolytes (SPEs) prepared by solution‐casting technique, using polyethylene oxides (PEO) doped with KCl salt in different weight percentages. The effect of the dopant on the chemical interactions and structural, optical, thermal, electrical, and electrochemical properties were studied using various strategies. It was found that the incorporation of KCl salt to PEO results in a three order of magnitude enhancement in ionic conductivity of polymer matrix from 10−9 to 10−6 S cm−1. The PEO doped with 20 wt.% KCl salt exhibited the highest ionic conductivity (4.32 × 10−6 S cm−1) and low activation energy (0.25 eV). According to the thermal analysis, the thermal stability of the films improved as the dopant concentration increased. Further, the electrochemical strength improved with increasing dopant concentration, according to cyclic voltammogram experiments. From the results of all the characterizations, PEO loaded with 20 wt.% KCl SPE system is a suitable candidate for use as an electrolyte in energy storage devices such as solid‐state batteries.

Enhanced energy storage properties of (Ba0.4Sr0.6)TiO3 ceramics with ultrahigh energy efficiency through doping of Bi0.2Sr0.7(Mg1/3Nb2/3)O3

Dielectric (Ba0.4Sr0.6)TiO3 (BST) ceramics are promising dielectric energy storage materials due to their moderate dielectric constant, low dielectric loss, and slight nonlinearity. However, their energy density is limited by their low breakdown strength (BDS). In this study, we aimed to address this limitation by incorporating various amounts of Bi0.2Sr0.7(Mg1/3Nb2/3)O3 (SBMN) into the BST matrix. The (1–x)BSTxSBMN ceramics were prepared by conventional solid-state sintering, resulting in single-phase solid solutions. Compared to pure BST ceramics, the (1–x)BST–xSBMN ceramics exhibited lower remnant polarization and significantly enhanced BDS. Furthermore, the relaxation of the ceramics enhanced with increasing doping concentration, with an efficiency of η = 94.0% achieved at x = 0.20. Among them, the breakdown field strength of 0.85BST–0.15SBMN ceramics was 597 kV cm−1, achieving a recoverable energy storage density of Wrec = 2.81 J cm−3 and an efficiency of η = 90.8% under an external electric field of 480 kV cm−1. Subsequent tests revealed that the introduction of SBMN not only increased the band gap and conduction activation energy of the material, leading to an increase in BDS, but also promoted the formation of polar nanoregions (PNRs) which contributed to boosted energy efficiency, resulting in a significant enhancement in the energy storage performance of BST ceramics.

The influence of defects on conduction processes in chalcogenide semiconductor compounds

Due to the strong dependence on the intrinsic defectiveness of structures, semiconductor compounds based on metal chalcogenides have a wide spread in kinetic properties and high growth temperatures of materials, as well as a tendency to self-compensation of defects. It has been shown that an increase in defectivity in the cation sublattice leads to a decrease in ionic conductivity in copper chalcogenides, and an increase in temperature leads to an increase in ionic conductivity due to a change in mobility. The low activation energy indicates a strong intrinsic disorder of the cation part of the lattice. In copper chalcogenides, the presence of hopping conductivity at small deviations from stoichiometry is explained by compensation and a high concentration of vacancies. Under such conditions, this activation energy is the activation energy for the movement of copper ions throughout the crystal and almost all metal ions contribute to the ionic electrical conductivity. In semiconductor compounds based on metal chalcogenides with deviations from stoichiometry, the activation energy of cationic conductivity does not change, since the defects that arise in this case do not introduce large changes in ionic conductivity with temperature. The increase in ionic conductivity with increasing temperature is due to a change in mobility, since the carrier concentration remains unchanged. The latter is determined only by the structural features of the phases. Deviation from stoichiometry in compounds makes it necessary to take into account the movement of the main charge carriers in the allowed zones, and the movement of carriers along vacancies. The properties of metal chalcogenides are largely determined by the characteristics of their preparation and depend on the relative ratio of metal and chalcogen atoms, as well as the presence of intrinsic defects and their influence on the mechanism of behavior of charge carriers and transfer phenomena.

Electrical Resistivity Behavior and Small Polaron Conduction Transport Mechanism in Semiconducting <I>R</I>MnO<sub>3</sub> Manganites

Rare earth manganites, denoted by the chemical formula <I>R</I>MnO<sub>3</sub>, where <I>R</I> signifies a rare earth element, have garnered significant interest in recent years. These perovskite oxides exhibit intriguing phenomena such as multiferroicity, ferroelectricity, and colossal magnetoresistance, primarily attributed to the role of polarons in conduction. The incorporation of rare earth ions imparts flexibility, making these compounds promising for applications in spintronics, sensors, and information storage devices. This study delves into the electrical resistivity behavior and Small Polaron Conduction (SPC) mechanisms of rare earth manganites, particularly <I>R</I>MnO<sub>3</sub>. In this manuscript, electrical resistivity of the pristine <I>R</I>MnO<sub>3</sub> (<I>R</I> = Sm, Eu, Gd) manganites are analyzed within the framework of adiabatic nearest-neighbor hopping of SPC. The high temperature state of <I>R</I>MnO<sub>3</sub> within the SPC mechanism is influenced by polaron concentration, hopping distance, and resistivity coefficient. The localized charge carriers in undoped manganites enable one to estimate the activation energy for the electrical conduction. The activation energy decreases with the decrease in ionic radii from Sm to Gd. Deduced polaron activation energy is low for GdMnO<sub>3</sub> as compared to SmMnO<sub>3</sub> and is attributed to reducing disorder state in GdMnO<sub>3</sub> as compared to SmMnO<sub>3</sub>. This work contributes to the fundamental understanding of condensed matter physics and the potential applications of rare earth manganites in emerging technologies. The interplay between electrical resistivity and Small Polaron Conduction offers insights for customizing these materials for specific technological needs.

High-temperature transport properties of entropy-stabilized pyrochlores

In this report, the high-temperature transport properties of (Dy1−xCax)(Zr0.2Hf0.2Sn0.2Ti0.2Ge0.2)O7 pyrochlore oxides with x = 0, 0.05, and 0.1 are studied in dry and humid air. The phase composition and crystal structure were determined by using x-ray and neutron diffraction. The addition of calcium to the structure caused an increase in the concentration of oxygen vacancies, indicating an ionic charge compensation mechanism. Electrical studies allowed us to determine the total electrical conductivity as a function of the synthesis atmosphere and pH2O. The electrical conductivity turned out to be at the level of ∼10−3 S/cm at 800 °C, and only a slight effect of the presence of protonic defects in the structure on the total electrical conductivity was observed. In general, the samples had a low electrical conductivity with a relatively high activation energy of conduction.

Recent Novel Fabrication Techniques for Proton-Conducting Solid Oxide Fuel Cells

Research has been conducted on solid oxide fuel cells (SOFCs) for their fuel flexibility, modularity, high efficiency, and power density. However, the high working temperature leads to the deterioration of materials and increased operating costs. Considering the high protonic conductivity and low activation energy, the proton conducting SOFC, i.e., the protonic ceramic fuel cell (PCFC), working at a low temperature, has been wildly investigated. The PCFC is a promising state-of-the-art electrochemical energy conversion system for ecological energy; it is characterized by near zero carbon emissions and high efficiency, and it is environment-friendly. The PCFC can be applied for the direct conversion of various renewable fuels into electricity at intermediate temperatures (400–650 °C). The construction of the PCFC directly affect its properties; therefore, manufacturing technology is the crucial factor that determines the performance. As a thinner electrolyte layer will lead to a lower polarization resistance, a uniformly constructed and crack-free layer which can perfectly bond to electrodes with a large effective area is challenging to achieve. In this work, different fabrication methods are investigated, and their effect on the overall performance of PCFCs is evaluated. This article reviews the recent preparation methods of PCFCs, including common methods, 3D printing methods, and other advanced methods, with summarized respective features, and their testing and characterization results.

Enhancing sintering behavior and conductivity of YSZ electrolyte by co-doping of ZnO and MnO2

This study aimed to enhance the sinterability and conductivity of yttria fully stabilized zirconia electrolyte through co-doping by 2 mol% of ZnO and different contents of MnO2 (0, 0.5, 1, 1.5 mol%) at two sintering temperatures of 1300 and 1400 °C. Phase composition identification, density, microstructure, and conductivity of the samples were evaluated using X-ray diffraction (XRD), Archimedes' method, field emission scanning electron microscopy (FESEM), and electrochemical impedance spectroscopy (EIS), respectively. The XRD results revealed that ZnO and MnO2 are successfully doped in the fluorite structure of YSZ sintered at 1400 °C, and the cubic structure is completely preserved. However, at a sintering temperature of 1300 °C, the (111) peaks of doped samples were slightly split, which implied a slight phase transformation of YSZ from cubic to a tetragonal structure. The co-doped samples, at both sintering temperatures, showed higher relative density and grain size compared with pure YSZ. The addition of 2 mol% of ZnO and 0.5 mol% of MnO2 at 1400 °C increased the relative density of YSZ from 81.6% to 95.1%. The increase in relative density and grain size, while maintaining the cubic structure, caused an increase in the conductivity of the mentioned sample. Compared with pure YSZ, the sample's total conductivity increased from 7.37 to 10.03 S m−1 at 800 °C. The proposed composition showed better sintering behavior, lower activation energy of grain conductivity, and higher conductivity than pure YSZ. This behavior is thought to be due to the facilitating rearrangement of atoms during sintering and an increase in oxygen ion vacancy concentration due to co-doping with the appropriate amount of ZnO and MnO2.

Enhanced mechanical, electrical, thermal, and optical properties of poly(methyl methacrylate)/copper oxide nanocomposites for flexible optoelectronic devices via in‐situ polymerization technique

AbstractPolymethyl methacrylate (PMMA) with varied compositions of copper oxide (CuO) nanoparticles was synthesized using in‐situ free radical polymerization. UV–visible, FT‐IR, XRD, FE‐SEM, DSC, and TGA were employed to examine their structure, morphology, and thermal properties. The broadening and intensification of UV absorption, as well as the shift in IR peaks of PMMA with the addition of CuO, confirm their interactions. The reduction in optical bandgap values with the reinforcement of nanofillers confirms the existence of intermediate energy bands in nanocomposites. XRD indicated that polymerization with CuO reduced the amorphous nature of PMMA. The FE‐SEM image revealed that the dispersion of CuO altered the nonporous, rough surface of PMMA into a homogeneous shape. The reinforcement of CuO enhanced the thermal stability and glass transition temperature of PMMA. The mechanical strength, modulus, impact strength, and rigidity of PMMA were significantly improved through in‐situ polymerization. The electrical property analysis revealed that the AC conductivity increased with frequency, temperature, and filler content. The reduction in activation energy of AC conductivity with temperature points toward their semiconducting nature. PMMA/CuO nanocomposites with higher tensile strength, lower bandgap energy, higher conductivity, and thermal properties can be used to make flexible optoelectronic devices.Highlights A series of PMMA/CuO nanocomposites were synthesized and characterized. Enhanced optical property, thermal stability, and glass transition temperature. Possess excellent dielectric constant and AC conductivity. Mechanical strength and impact resistance of PMMA were greatly enhanced. A promising material for flexible optoelectronic and power storage applications.

Effect of Donor Nb(V) Doping on the Surface Reactivity, Electrical, Optical and Photocatalytic Properties of Nanocrystalline TiO2.

In this work, we primarily aimed to study the Nb(V) doping effect on the surface activity and optical and electrical properties of nanocrystalline TiO2 obtained through flame-spray pyrolysis. Materials were characterized using X-ray diffraction, Raman spectroscopy and IR, UV and visible spectroscopy. The mechanism of surface reaction with acetone was studied using in situ DRIFTs. It was found that the TiO2-Nb-4 material demonstrated a higher conversion of acetone at a temperature of 300 °C than pure TiO2, which was due to the presence of more active forms of chemisorbed oxygen, as well as higher Lewis acidity of the surface. Conduction activation energies (Eact) were calculated for thin films based on TiO2-Nb materials. The results of the MB photobleaching experiment showed a non-monotonic change in the photocatalytic properties of materials with an increase in Nb(V) content, which was caused by a combination of factors, such as specific surface area, phase composition, concentration of charge carriers as well as their recombination due to lattice point defects.