Defect Concentration Research Articles

Investigation of the CMAS thermal corrosion resistance of novel Al2O3/YTaO4 thermal barrier coatings

In this paper, atmospheric plasma spraying was used to produce YTaO4 thermal barrier coatings and 10 wt% Al2O3-YTaO4 thermal barrier coatings. The coatings were heated to temperatures of 1300 °C and 1600 °C, respectively. The corrosion resistance and mechanism of the coatings against CMAS corrosion at 1250 °C for 10 h and 50 h were then investigated. This study revealed that during CMAS thermal corrosion, the primary corrosion products were anorthite, apatite, and Ca2Ta2O7. Apatite and Ca2Ta2O7 formed a compact layer at the boundary between the reaction layer and the coating layer, effectively blocking CMAS melt infiltration in a downward direction. As the heated temperature increased, the volume expansion resulting from the phase transformation and the closure of pores and microcracks within the coating caused the coated surface to become denser. The corrosion rate of the coatings was reduced due to a reduction in grain boundaries and a lower concentration of defects in the grain boundary regions. This improved the resistance of coatings to CMAS thermal corrosion. The presence of Al2O3 facilitated the formation of anorthite in the CMAS melt. Excessive anorthite can form a thick network that hinders the penetration of the CMAS melt. Meanwhile, it increased the viscosity of the melt and reduced its ability to spread, resulting in a slower rate of penetration by the CMAS melt. This, in turn, improved the coatings' ability to withstand thermal corrosion caused by CMAS.

Balancing Carrier Dynamics in Oxygen-Vacancy-Tuned Amorphous Ga2O3 Thin-Film Self-Powered Photoelectrochemical-Type Solar-Blind Photodetector Arrays for Underwater Imaging.

Underwater imaging technology plays a pivotal role in marine exploration and reconnaissance, necessitating photodetectors (PDs) with high responsivity, fast response speed, and low preparation costs. This study presents the synergistic optimization of responsivity and response speed in self-powered photoelectrochemical (PEC)-type photodetector arrays based on oxygen-vacancy-tuned amorphous gallium oxide (a-Ga2O3) thin films, specifically designed for solar-blind underwater detection. Utilizing a low-cost one-step sputtering process with controlled oxygen flow, a-Ga2O3 thin films with varying oxygen vacancy (VO) concentrations are fabricated. By balancing the trade-offs among electrocatalytic reactions, charge transfer, carrier recombination, and trapping, both the responsivity and response speed of a-Ga2O3-based self-powered PEC-PDs are simultaneously improved. Consequently, the optimized PEC-PDs demonstrated exceptional performance, achieving a responsivity of 33.75mA W-1 and response times of 12.8ms (rise) and 31.3ms (decay), outperforming the vast majority of similar devices. Furthermore, a pronounced positive correlation between anomalous transient photocurrent spikes and the concentration of VO defects is observed, offering compelling evidence for VO-mediated indirect recombination. Finally, the proof-of-concept solar-blind underwater imaging system, utilizing an array of self-powered PEC-PDs, demonstrated clear imaging capabilities in seawater. This work provides valuable insight into the potential for developing cost-effective, high-performance a-Ga2O3 thin-film-based PEC-PDs for advanced underwater imaging technology.

Effect of Ce-doping on the structural, morphological, and electrochemical features of Co3O4 nanoparticles synthesized by solution combustion method for battery-type supercapacitors

This study investigates the potential of cerium (Ce) doping to improve the performance of cobalt oxide (Co₃O₄) nanoparticles as battery-type supercapacitor electrodes. Pure Co₃O₄ nanoparticles were synthesized via a solution combustion method and then doped with 2.5 % (Ce-Co3O4) and 5 % Ce (CeO2-Co3O4). Comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), was used to analyze the impact of Ce doping on the material properties. XRD analysis confirmed the successful incorporation of Ce into the Co₃O₄ structure, with distinct CeO2 phases forming at higher doping levels. Ce doping resulted in decreased crystallite size and peak intensity, indicating reduced crystallinity and increased defect concentration. Raman spectroscopy corroborated these findings, showing a redshift that suggests weakened metal-oxygen bonds and smaller grain sizes due to Ce³⁺ incorporation. FESEM images demonstrated that Ce doping effectively reduced nanoparticle agglomeration, with 2.5 % doping leading to smaller particles and 5 % doping promoting a 2D flake-like morphology with increased porosity. Nitrogen adsorption-desorption measurements revealed a significant increase in surface area and pore volume for CeO2-Co₃O₄, facilitating improved electrolyte diffusion and reduced resistance, thereby enhancing electrochemical performance. Evaluation of the electrochemical properties of undoped and Ce-doped Co₃O₄ materials revealed a battery-like response in a three-electrode configuration. Notably, the CeO2-Co3O4 exhibited a superior specific capacity of 603.3 C g−1 at a current density of 1 A g−1, significantly exceeding the values of 368.5 C g−1 and 127.1 C g−1 achieved by Ce-Co3O4 and undoped Co3O4, respectively. Furthermore, the CeO2-doped Co3O4 demonstrated exceptional cyclic stability, retaining 87 % of its initial capacity after undergoing 5000 charge-discharge cycles at a high current density of 10 A g−1. These results suggest that Ce doping is a promising strategy for optimizing Co₃O₄-based battery-type electrode materials, potentially leading to the development of high-performance and cost-effective energy storage systems.

Upcycling the Spent Graphite Anode Into the Prelithiation Catalyst: A Separator Strategy Toward Anode-Free Cell Prototyping.

The substantial manufacturing of lithium-ion batteries (LIBs) requires sustainable, circular, and decarbonized recycling strategies. While efforts are concentrated on extracting valuable metals from cathodes using intricate chemical process, the direct, efficient cathode regeneration remains a technological challenge. More urgently, the battery supply chain also requires the value-added exploitation of retired anodes. Here, a "closed-loop" approach is proposed to upcycle spent graphite into the prelithiation catalyst, namely the fewer-layer graphene flakes (FGF), upon the exquisite tuning of interlayer spacing and defect concentration. Since the catalytic FGF mitigates the delithiation energy barrier from calcinated Li5FeO4 nanocrystalline, the composite layer of which cast on the polyolefin substrate thus enables a customized prelithiation capability (98% Li+ utilization) for the retired LiFePO4 recovery. Furthermore, the hydrophobic polymeric modification guarantees the moisture tolerance of Li5FeO4 agents, aligning with commercial battery manufacturing standards. The separator strategy well regulates the interfacial chemistry in the anode-free pouch cell (LiFePO4||Cu), the prototype of which balances the robust cyclability, energy density up to 386.6Wh kg-1 as well as the extreme power output of 1159.8W kg-1. This study not only fulfills the sustainable supply chain with graphite upcycling, but also establishes a generic, viable protocol for the anode-free cell prototyping.

Defect related anomalous mobility of small polarons in dielectric oxides at the example of congruent lithium niobate

Polarons play a major role in the description of optical, electrical and dielectrical properties of several ferroelectric oxides. The motion of those particles occurs by elementary hops among the material lattice sites. In order to compute macroscopic transport parameters such as charge mobility, normal (i.e. Fickian) diffusion laws are generally assumed. In this paper we show that when defect states able to trap the polarons for long times are considered, significant deviations from the normal diffusion behaviour arise. As an example of this behavior, we consider here the case of lithium niobate (LN). This can be considered as a prototypical system, having a rich landscape of interacting polaron types and for which a significant wealth of information is available in literature. Our analysis considers the case of a stoichiometric, defect-free lithium niobate containing a certain concentration of small electron polarons hopping on regular Nb sites, and compares it to the material in congruent composition, which is generally found in real-life applications and which is characterized by a large concentration of antisite NbLi defects. While in the first case the charge carriers are free polarons hopping on a regular Nb sublattice, in the second case a fraction of polarons is trapped on antisite defects. Thus, in the congruent material, a range of different hopping possibilities arises, depending on the type of starting and destination sites. We develop a formalism encompassing all these microscopic processes in the framework of a switching diffusion model which can be well approximated by a mobile–immobile transport model providing explicit expressions for the polaron mobility. Finally, starting from the Marcus–Holstein’s model for the polaron hopping frequency we verify by means of a Monte Carlo approach the diffusion/mobility of the different polarons species showing that, while free polarons obey the laws for normal diffusion as expected, bound polarons follow an anomalous diffusion behaviour and that in the case of the congruent crystal where mixed free and bound polaron transport is involved, our expressions indeed provide a satisfactory description.

Optical and microstructural studies of erbium-doped TiO2 thin films on silicon, SrTiO3, and sapphire

Rare-earth ion doped oxide thin films integrated on silicon substrates provide a route toward scalable, chip-scale platforms for quantum coherent devices. Erbium-doped TiO2 is an attractive candidate: the Er3+ optical transition is compatible with C-band optical fiber communications, while TiO2 is an insulating dielectric compatible with silicon process technology. Through structural and optical studies of Er-doped TiO2 thin films grown via molecular beam deposition on silicon, SrTiO3, and sapphire substrates, we have explored the impact of polycrystallinity and microstructure on the optical properties of the Er emission. Comparing polycrystalline TiO2(rutile)/Si with single-crystalline TiO2(rutile)/r-sapphire and polycrystalline TiO2(anatase)/Si with single-crystalline TiO2(anatase)/SrTiO3, we observe that the inhomogeneous linewidth (Γinh) of the most prominent peak in the Er spectrum (the Y1–Z1 transition, 1520 and 1533 nm in rutile and anatase TiO2) is significantly narrower in the polycrystalline case. This implies a relative insensitivity to extended structural defects and grain boundaries in such films (as opposed to, e.g., point defects). We show that the growth of an undoped, underlying TiO2 buffer on Si can reduce Γinh by a factor of 4–5. Expectedly, Γinh also reduces with decreasing Er concentrations: we observe a ∼2 order of magnitude reduction from ∼1000 ppm Er to ∼10 ppm Er. Γinh then gets limited to a residual value of ∼5 GHz that is insensitive to further reduction in the Er concentration. Based upon the above results, we argue that the optical properties in these thin films are limited by the presence of high “grown-in” point defect concentrations.

The connection between the accumulation of structural defects caused by proton irradiation and the destruction of the near-surface layer of Li4SiO4 – Li2TiO3 ceramics

The key problem of using lithium-containing ceramics as materials of breeders for the propagation of tritium in thermonuclear reactors is phase stability, as well as the preservation of strength and thermophysical parameters of ceramics during their operation, which is accompanied by the accumulation of fission products in the near-surface layers, alongside mechanical influences from the outside. Moreover, in contrast to other types of ceramics, the presence of lithium in the composition of the samples under study leads to limitations in the use of classical analysis methods (scanning electron microscopy, energy dispersive analysis or optical spectroscopy) of structural changes caused by the accumulation of radiation damage, which requires the use of more complex methods for the assessment of the defect concentration in the structure, as well as establishing their relationship with the deterioration of strength and thermophysical parameters, playing a key role in determining the stability mechanisms and further exploitation of ceramics for tritium production. In this regard, the aim of the study is to determine the kinetics of changes in the near-surface layer of two-phase Li4SiO4 – Li2TiO3 ceramics associated with the accumulation of structural distortions caused by irradiation, as well as their relationship with strain embrittlement and disorder. During the studies, it was found that the accumulation of implanted hydrogen in the near-surface layer under high-dose irradiation initiates deformation distortion processes, the intensity of which depends on the ratio of components in the ceramics, according to which the optimal compositions of two-phase ceramics are ratios of components from 0.3 to 0.6. Determination of the type of defects in the composition of the damaged layer, as well as their concentration, was carried out using the electron spin resonance (ESP) method. During the studies, it was found that at low irradiation fluences, the dominant role in the accumulation of structural defects is played by vacancy defects associated with E′-centers, the formation of which is associated with structural distortions, while as the fluence grows, the structure is dominated by deformation disordering caused by the accumulation of Ti3+ defects and HC2 centers (SiO43-), the concentrations of which have a clear dependence on the phase composition of the ceramics.

Enhanced performance of photocatalytic oxidation of indoor toluene over Pd/TiO2 catalyst by tuning surface defect concentrations

An effective approach for the elimination of indoor gaseous toluene through photocatalytic oxidation involves the engineering of surface defects on catalysts. In this study, the concentrations of surface oxygen defects in PdTi-xN (x = 10, 30) catalysts were controlled using the sodium borohydride solid-phase reduction method, and their performances in the photocatalytic oxidation of indoor gaseous toluene were evaluated. PdTi–10 N demonstrated high photocatalytic efficiency for toluene oxidation, achieving 84% toluene conversion and approximately 75% CO2 mineralization. Characterization results indicated that surface oxygen defects can enhance the separation of photo-generated electrons and holes, facilitating their interaction with Pd0 species to form Ti3+ species. More reactive oxygen species (·OH-and ·O2−) were generated on PdTi–10 N due to the synergistic effect of surface oxygen defect and Ti3+ species, which played a significant role as the toluene oxidation. This work provides a new insight for the design and development of high-performance Pd/TiO2 catalysts in the field of indoor VOCs treatment.

Enabling defect control or polyiodide formation regimes in halide perovskites

Defect engineering in oxide materials is typically achieved through manipulation of oxygen pressure and temperature, followed by quenching which freezes the concentration of point defects. Unlike oxides, halide perovskites equilibrate with gaseous atmosphere at room temperature. Information on defect engineering in halide perovskites that utilize the concentration of gaseous species is scarce and controversial. In this report we address this controversy by studying the interaction of MAPbI3 with molecular iodine over a wide range of partial pressures and reveal the two regimes of such interaction: defect control regime and polyiodide formation regime switching at ∼20 % of the saturated iodine pressure. In defect control regime the material undergoes reversible changes in semiconductor properties, while in polyiodide formation regime the material undergoes irreversible changes in crystallinity and microstructure. These findings emphasize the manifold role of molecular iodine for this class of materials and provides researchers with the experimental framework that can be utilized to tune stoichiometry and conductivity of halide perovskites to further enhance the performance and stability metrics of the corresponding devices.

A Self-Constructed Mg2+/K+ Co-Doped Prussian Blue with Superior Cycling Stability Enabled by Enhanced Coulombic Attraction.

Prussian blue (PB) is regarded as a promising cathode for sodium-ion batteries because of its sustainable precursor elements (e.g., Mn, Fe), easy preparation, and unique framework structure. However, the unstable structure and inherent crystal H2O restrain its practical application. For this purpose, a self-constructed trace Mg2+/K+ co-doped PB prepared via a sea-water-mediated method is proposed to address this problem. The Mg2+/K+ co-doping in the Na sites of PB is permitted by both thermodynamics and kinetics factors when synthesized in sea water. The results reveal that the introduced Mg2+ and K+ are immovable in the PB lattices and can form stronger K‒N and Mg‒N Coulombic attraction to relieve phase transition and element dissolution. Besides, the Mg2+/K+ co-doping can reduce defect and H2O contents. As a result, the PB prepared in sea water exhibits an extremely long cycle life (80.1% retention after 2400 cycles) and superior rate capability (90.4% capacity retention at 20 C relative to that at 0.1 C). To address its practical applications, a sodium salts recycling strategy is proposed to greatly reduce the PB production cost. This work provides a self-constructed Mg2+/K+ co-doped high-performance PB at a low preparation cost for sustainable, large-scale energy storage.

Characterization Study of Deep-Level Defect Spatial Distribution, Emission Mechanisms, and Structural Identification

Abstract The characterization of defects in semiconductor materials and devices is crucial for enhancing the performance and reliability of semiconductor products. This tutorial review focuses on Deep Level Transient Spectroscopy (DLTS) as the primary analytical tool, thoroughly discussing its distinct advantages in deep-level defect characterization. However, it is unable to reveal the concentration-depth distribution of deep-level defects, neglects the dependency of carrier emission rates on the electric field, and fails to accurately identify defect structures.
To overcome these limitations, two enhanced DLTS techniques have been developed to extend the capabilities of DLTS. These enhancements include the utilization of graded fill pulse technology to accurately map defect distributions at various depths within devices, facilitating individual defect characterization across different layers of multilayered structures; the application of varying electric field strengths to samples to delve into the intricate physical mechanisms of defects during carrier emission processes; and the adjustment of the duration of electric pulse injection to monitor signal growth trends, deducing the microstructure of defects. The paper integrates research findings from a wide array of field experts, meticulously outlines a description of how to obtain the depth distribution of defect concentration in devices, furnishes quantitative criteria for both the Poole-Frenkel effect and phonon-assisted tunneling mechanisms of carrier emission, and provides specific examples for distinguishing between interface states/bulk defects and point defects/extended defects. This enhances both the theoretical and practical knowledge in this field. The advanced DLTS techniques outlined provide crucial guidance for defect characterization and performance optimization in semiconductor devices with new structures and materials.

Bottom-up construction of defective TiO2 microspheres with hierarchical architectures and controlled crystallites for visible-light photocatalysis

Defect-engineering of TiO2 materials has emerged as an effective strategy to enhance the light adsorption and improve the photocatalytic activity under visible-light. However, the designing and fabricating of hierarchically structured TiO2 with controllable crystalline phases and stable structure defects is challenging and rarely reported. Herein, we present a novel bottom-up synthesis strategy to prepare defective TiO2 microspheres with hierarchical architecture and abundant phase junctions. The phase composition and defect concentration of the obtained TiO2 can be easily adjusted by regulating the amount of urea. Moreover, the formation mechanism of hierarchical defective TiO2 microspheres has been investigated. Notably, compared with the defective TiO2 prepared with traditional top-down strategies, more bulk Ti3+ and oxygen vacancies can be generated, which is crucial for the stability of materials. Such integration of unique hierarchical architecture, stable structure defects as well as abundant anatase/rutile phase junctions not only result in the narrowed band gap and improved visible-light absorption, but also allow the fast interfacial electron transfer and better charge separation, leading to enhanced photocatalytic activities in RhB degradation and hydrogen generation under visible light (λ>400 nm) irradiation.

Enhancing the Acidity Window of Zeolites by Low-Temperature Template Oxidation with Ozone.

Revisiting the impact of the first and often deemed trivial postsynthetic step, i.e., a high-temperature oxidative calcination to remove organic templates, increases our understanding of thermal acid site evolution and Al distributions. An unprecedented degree of control over the acidity of high-silica zeolites (SSZ-13) was achieved by using a low-temperature ozonation approach. Fourier transform infrared spectroscopy of adsorbed probe molecules and solid-state NMR spectroscopy reveal the complexity of the thermal evolution of acid sites. Low-temperature activated (ozonated) zeolites maintain the original Brønsted acidity content and high defect content and have virtually no Lewis acidity. They also preserve the "as-made" Al distribution after crystallization and show a clear link between synthesis conditions and divalent cation capacity, as measured with aqueous cobalt ion uptake. The synthesis protocol is found to be the main contributor to Al proximity, yielding record high exchange capacity when ozonated. After conventional calcination at 500-600 °C, however, the presence of water leads to the gradual depletion of Brønsted acid sites, in particular, in small crystals. This work indicates that low-temperature ozonation followed by thermal activation at different temperatures can be used as a novel tool for tuning the amount and nature of acid sites, providing insights into the activity of zeolites in acid-catalyzed reactions, such as CO2 hydrogenation to dimethyl ether, and thereby expanding the possibilities of rational acidity tuning.

An insight in to microwave induced defects and its impact on nonlinear process in NiO nanostructures under femtosecond and continuous wave laser excitation.

This work demonstrates the impact of microwave (MW) irradiation on third-order nonlinear optical (NLO) processes in chemically deposited NiO nanostructure films. The optical nonlinearity of the NiO nanostructure films was studied using third-harmonic generation (THG) measurements in the pulsed femtosecond laser regime and the Z-scan technique in the continuous wave laser regime. In the ultrafast pulsed regime, THG measurements revealed a significant increase in the THG signal of MW-irradiated NiO nanostructures due to photoexcitation and relaxation processes, resulting from an enhancement in defect concentration. This increase in defect density upon MW irradiation was quantified by PL and XPS studies. Under continuous wave laser irradiation, the Z-scan technique showed an enhanced absorption coefficient of ∼10-1 m W-1 and a nonlinear refractive index of ∼10-7 m2 W-1. The high NLO values in both pulsed and continuous laser regimes indicate that MW-irradiated NiO nanostructure films hold promise for optoelectronic device applications.

Chemiresistive detection of xylene vapor using MOF-derived porous Co3O4 microrods activated by Mo6+ cations

Incorporation of high-valence cation into catalytic oxide (eg. Co3O4) is favorable for regulating the carrier concentration and creating more active centers for surface reaction process, thus promoting the sensing capability towards low reactive gas (eg. xylene). Herein, the metal-organic framework (MOF)-derived Mo-doped porous Co3O4 microrods are achieved through a simple solution method combing with a thermal method. The introduction of Mo6+ into Co3O4 matrix enhances the concentration of oxygen defects and Co3+, coupled with the specific surface area. As a result, the 5 at% Mo/Co3O4-based gas sensor sample exhibits a nice selectivity, clear response value (Rg/Ra=29.8 – 100 ppm), low concentration limit (0.5 ppm), and reliable stability to xylene vapor under a low working temperature (140 °C). Moreover, the possible reaction pathway (benzyl-benzaldehyde-benzoate-aromatic ester/anhydride) of xylene oxidation over this 5 at% Mo-doped Co3O4 microrod is proved by an in-situ DRIFTS analysis. Importantly, this optimized xylene-sensing capability is further discussed from the viewpoint of Mo-introducing effect into the porous Co3O4 microrods. This work further demonstrates a reliable approach of high valence cation-doped catalytic oxides to detect low reactive vapor.

The effect of ion implantation and annealing temperatures on the migration behavior of ruthenium in glassy carbon

Nuclear waste storage materials are inevitable in nuclear industry for preventing the release of radioactive waste products. Glassy carbon has been considered being beneficial to be used in the dry cask needed for nuclear waste storage. Thus, we studied the migration of ruthenium implanted in glassy carbon upon annealing. Our investigations show that ruthenium implantation caused defects in the glassy carbon structure, with more defects observed in the room temperature as-implanted samples compared to those implanted at 200 °C. Annealing the as-implanted samples from 500 to 800 °C showed no significant change in the ruthenium depth profiles, indicating the non-diffusivity of ruthenium in glassy carbon at these temperatures. However, annealing at higher temperatures (from 900 and 1300 °C) resulted in an increase in the maximum depth profile peaks, accompanied by a shift towards the surface, and a decrease in the full-width at half-maximum. These changes indicate the aggregation of ruthenium atoms in the near-surface region. Additionally, more ruthenium aggregation was observed in room temperature implanted samples compared to those implanted at 200 °C. This difference is attributed to the higher concentration of defects in room temperature implanted samples, which promotes ruthenium aggregation. Moreover, the migration and aggregation of ruthenium in the near-surface region contributed to an increase in the surface roughness of the glassy carbon.

Incorporation of specific defects through ion bombardment for better ferroelectrics

AbstractIncorporating specific defects into complex oxides facilitates the exploration of exotic phenomena and novel functionalities based on the intricate coupling between the defects and lattice/charge. However, methods for maximizing the density of specific defects while enhancing the desired properties have been rarely explored. In this study, the effect of N+ ion bombardment‐driven specific defects on the properties of bismuth ferrite (BFO) thin films was investigated. Furthermore, atomic structure characterization and computational processing revealed the displacement and orientation of the Fe atoms, which are linearly related to the degree of polarization. The ion bombardment introduced deep‐level trap states within the lattice, leading to a significant reduction in the leakage current and improved insulation performance of the films. By precisely engineering the defect content through N+ ion bombardment, the pure BFO thin films with remarkable and stable ferroelectric properties (remnant polarization, Pr = ∼116.8 µC·cm−2; leakage current, J = ∼1.5 × 10−8 A·cm−2) were fabricated. This innovative defect engineering‐based approach enables the customization and optimization of local ferroelectric order parameters, thereby establishing a solid foundation for designing functionalities across various functional material systems.

Defect-rich carbon nanosheets derived from p(C3O2)x for electromagnetic wave absorption applications

Defect modulation strategies have been shown to be an effective way to design efficient EMW absorbing materials, but the coexistence of multiple loss mechanisms due to the complexity of the existing models makes it difficult to elucidate the mechanism by which defect-induced dielectric losses dominate. In this work, p(C3O2)x is applied for the first time in the field of EMW absorption and the concentration of defects in the sample is controlled by changing the pyrolysis temperature. In addition, the unique molecular structure of p(C3O2)x enables the prepared samples to completely eliminate the interference of interfacial polarization and magnetic loss on EMW dissipation. The results show that the dielectric loss induced by defects significantly enhances the EMW absorption performance as the concentration of defects increases, but excessive defects lead to a sudden drop in the conductivity of the sample and reduce the EMW absorption performance. In which, the RLmin of OC-800 can reach −51.0 dB, and the EAB of OC-900 can go up to 5.6 GHz at only 1.6 mm. Finally, CST simulation verified the potential application of the prepared absorber in real scenarios. This work has improved the theoretical basis of the effect of defect-induced dielectric loss on EMW absorbing properties, and the simple synthetic raw materials and routes have made the industrialized production of highly efficient EMW absorbing materials possible.

Graphene oxide-mediated polymorphic engineering of In2O3 for boosted NO2 gas sensing performance

Nitrogen dioxide (NO2) is a serious menace to human health and the environment, it is of great practical meaning to develop a fast and accurate gas sensor for monitoring low-concentration NO2 at near room temperature (RT). Here, the polymorphism of In2O3 was regulated with controllable mixed-phase ratios of hexagonal In2O3 (h-In2O3) and cubic In2O3 (c-In2O3) via a graphene oxide (GO)-mediated solvothermal approach and annealing treatment. The GO-mediation markedly promoted the formation of h-In2O3 and defect content. The morphology, specific surface area, surface chemical state and activation energy were roundly analyzed. The NO2-sensing performance results showed that the sensor based on an 8 wt% GO-mediated In2O3 sample (In2O3-8) exhibited an ultrahigh response of 1021 towards 1 ppm NO2 at 30℃, which was 2.3 times higher than that of In2O3 without GO-mediation. At the same time, the response/recovery time of In2O3-8 was significantly shorter than other sensors. Additionally, the In2O3-8 sensor possessed good repeatability and long stability. In2O3-8 with an appropriate GO-mediated content provided a suitable h-In2O3/c-In2O3 phase junction interface, abundant oxygen vacancies and elevated Fermi energy levels of In2O3, which activated the surface sites and ultimately enhanced the sensing performance.

Ultra-high energy storage characteristics under low electric field in Sm-doped Bi5Mg0.5Ti3.5O15 films through defect dipole engineering

The sol–gel method was used to fabricate lead-free Bi5-xSmxMg0.5Ti3.5O15 (BSxMTO, x = 0.25) relaxor ferroelectric film, which exhibited a recoverable energy storage density of 64 J/cm3 and an energy efficiency of 81.1 % under 1856 kV/cm. The energy storage response specifically reaches as high as 0.1824 J/kV·cm2. Enhancing the ergodic relaxor characteristics, improving the defect dipole driving, and reducing defect concentration are essential factors for BSxMTO (x = 0.25) film to collaboratively achieve enhanced relaxor characteristics and polarization intensity, thereby resulting in excellent medium- and low-field energy storage performances. Furthermore, the BSxMTO (x = 0.25) film also exhibits excellent stability in frequency (1 kHz − 20 kHz) (Ure ∼ (40.95 ± 1.01) J/cm3, η ∼ 85.7 % ± 4.4 %) and temperature (20 °C − 150 °C) (Ure ∼ (40.87 ± 0.30) J/cm3, η ∼ 80.4 % ± 2.2 %) under 1387 kV/cm, offering promising prospects for the application of lead-free dielectric energy storage films in low and medium electric fields.