Charge Compensation Research Articles

Chemical Competing Diffusion for Practical All-Solid-State Batteries.

The thermal safety issues of currently available Ni-rich cathode-based power supplies brought in the development of all-solid-state batteries, yet the cascade reactions in Ni-rich materials and the chemo-mechanical degradation between the cathode and solid electrolyte diminished the cycle life. Here, by introducing a new heteroatom chemical competing diffusion strategy, we successfully stabilize the Ni-rich cathode and the contact face with an solid electrolyte. Combining extensive explorations in theoretical calculation and multiscale in/ex situ characterization, we elucidate the atomic-level chemical competing diffusion upon the topological lithiation of layered materials. The heteroatoms with higher binding energy to the coordinated oxygen served as the "oxygen anchor" in the bulk and alleviated the excessive oxygen oxidation through charge compensation, thus easing the chemical aggression of the solid electrolyte by evolved oxygen. Comparably, others were enriched in the surface and formed an ionic "diffusion regulator" with residual lithium, and the special ionic transfer regulation mechanism of the piezoelectric layer validly improved the interface compatibility with the solid electrolyte and weakened the space-charge layer in solid-state batteries. This helped the designed Ni-rich cathode-based sulfide solid-state battery exhibit excellent cyclability under 4.5 V (97.3% after 120 cycles). Our findings unlocked the structure-function relationship between the polarization field generated by the piezoelectric material and the electrode.

High-quality 100% Ce3+:(Lu1-xYx)2SiO5 single crystals grown by the hydrothermal technique

Abstract The growth of Ce:(Lu1-xYx)2SiO5 single crystals by the hydrothermal technique is demonstrated. Crystallographic defects are suppressed thanks to the growth at much lower temperatures, and therefore, the complete incorporation of cerium in the Ce3+ valence state is obtained. The growth under supercritical water lowers the temperature to less than half of the melting point. In contrast, crystals grown from melt by the standard Czochralski technique possess intrinsic defects and undesirable Ce4+ ions as charge compensators. The growth of large-size single crystals with improved scintillation properties at a low cost is envisaged.

Controlling Ion Uptake in Carboxylated Mixed Conductors.

Organic mixed ionic-electronic conductors (OMIECs) have garnered significant attention due to their capacity to transport both ions and electrons, making them ideal for applications in energy storage, neuromorphics, and bioelectronics. However, charge compensation mechanisms during the polymer redox process remain poorly understood, and are often oversimplified as single-ion injection with little attention to counterion effects. To advance understanding and design strategies toward next-generation OMIEC systems, a series of p-channel carboxylated mixed conductors is investigated. Varying side-chain functionality, distinctive swelling character is uncovered during electrochemical doping/dedoping with model chao-/kosmotropic electrolytes. Carboxylic acid functionalized polymers demonstrate strong deswelling and mass reduction during doping, indicating cation expulsion, while ethoxycarbonyl counterparts exhibit prominent mass increase, pointing to an anion-driven doping mechanism. By employing operando grazing incidence X-ray fluorescence (GIXRF), it is revealed that the carboxyl functionalized polymer engages in robust cation interaction, whereas ester functionalization shifts the mechanism towards no cation involvement. It is demonstrated that cations are pivotal in mitigating swelling by counterbalancing anions, enabling efficient anion uptake without compromising performance. These findings underscore the transformative influence of functionality-driven factors and side-chain chemistry in governing ion dynamics and conduction, providing new frameworks for designing OMIECs with enhanced performance and reduced swelling.

Induced Charge Compensation effect for Boosting Photocatalytic Water Splitting in Covalent Organic Frameworks

Imine‐based covalent organic frameworks (COFs) are promising for photocatalytic water splitting, but their performance is often constrained by inefficient charge separation due to the high electron localization nature of polar imine bonds. In this study, we have optimized the electron delocalization across the imine linkage within a COF by implementing a charge compensation effect. This effect is achieved when a strong electron‐donating thieno[3,2‐b]thiophene linker is directly attached to the iminic carbon of a zinc‐porphyrinic COF. This modification significantly reduces the electron binding effect within the imine bonds of the COF, facilitating both in‐plane charge separation and out‐plane charge transfer to the catalytic site. Conversely, the use of strong electron‐withdrawing pyrizine linker aggravates the electron localization at the imine linkage in the ZnP‐Pz variant. Consequently, ZnP‐Tt shows a substantially improved photocatalytic water‐splitting activity under visible light irradiation, with a hydrogen evolution of 44288 ± 2280 μmol g–1 in 4 h, which exceeds the ZnP‐Pz counterpart by a factor of 10. These results offer fresh perspectives for the design of imine‐based COFs to overcome their limitations in charge separation efficiency.

Li diffusion in plagioclase crystals and glasses – implications for timescales of geological processes

Abstract. The growing interest in Li diffusion as a tool to determine timescales of short-time magmatic events, such as magma ascent during eruption, increases the necessity to better understand Li diffusion in common mineral phases. In this context, well-constrained diffusion coefficients and understanding of kinetic processes specific to mineral phases are of crucial importance. To gain further insight especially into the kinetic processes in plagioclase, we investigated the diffusion of Li between natural An61 plagioclase crystals and synthetic glasses of An80 plagioclase composition. Experiments were conducted at 200 MPa in rapid-heat/rapid-quench cold-seal pressure vessels (RH/RQ CSPVs) and internally heated pressure vessels (IHPVs) at temperatures between 606 and 1114 °C. Concentration and isotope profiles of Li were measured using femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS). We adopted a multispecies diffusion model and specified boundary conditions for plagioclase of labradoritic composition. Using this model, we were able to distinguish between an interstitial (DLii) and a vacancy process (DLiA), with the interstitial process being 0.2–1 orders of magnitude faster than the vacancy process, depending on temperature. DLii=10-3.76±0.58exp⁡-180.0±12.0kJmol-1RTm2s-1DLiA=10-5.53±0.16exp⁡-151.7±3.2kJmol-1RTm2s-1 Our data indicate charge compensation of Li by Na in both the crystal and the glass. Chemical Li diffusion coefficients in An80 glass are up to 3 orders of magnitude slower compared to Li tracer diffusion in silicate and aluminosilicate glasses and melts, which is attributed to slow Na diffusion at high An content. Our results for chemical diffusion of Li in plagioclase crystals are 1.5–2 orders of magnitude slower than Li tracer diffusion in An- and Ab-rich plagioclase determined in previous studies. This indicates that earlier studies on natural intermediate plagioclase compositions have underestimated timescales by up to 2 orders of magnitude. For accurate determination of timescales from Li diffusion in plagioclase we suggest further exploring the role of Na and a possible dependence on An content.

Cation‐Vacancy Engineering Modulated Perovskite Oxide for Boosting Electrocatalytic Conversion of Polysulfides

AbstractLithium‐sulfur batteries face challenges like polysulfide shuttle and slow conversion kinetics, hindering their practical applications in renewable energy storage and electric vehicles. Herein, a solution to solve this issue is reported by using a cation vacancy engineering strategy with rational synthesis of La‐deficient LaCoO3 (LCO‐VLa). The introduction of cation vacancies in LCO‐VLa modifies the geometric structure of coordinating atoms, exposing Co‐rich surface with more catalytically active surfaces. Meanwhile, the d‐band center of LCO‐VLa shifts toward the Fermi level, enhancing polysulfide adsorption. Furthermore, multivalent cobalt ions (Co3+/Co4+) induced by charge compensation enhance the electrical conductivity of LCO‐VLa, accelerating electron transfer processes and improving catalytic performance. Theoretical calculations and experimental characterizations demonstrate that La‐deficient LCO‐VLa effectively suppresses the polysulfide shuttle, reduces the energy barrier for polysulfide conversion, and accelerates redox reaction kinetics. LCO‐VLa‐based batteries demonstrate exceptional rate performance and cycling stability, retaining 70% capacity after nearly 500 cycles at 1.0 C, with a minimal decay rate of 0.055% per cycle. These findings highlight the significance of cation vacancy engineering for exploring precise structure‐activity relationships during polysulfides conversion, facilitating the rational design of catalysts at the atomic level for lithium‐sulfur batteries.

Insight into heterovalent metal modification for lanthanum carbonate to enhance phosphate removal at trace levels

Reducing phosphate concentrations from low levels to ultra-low levels (e.g., below 0.01 mg P/L) is crucial for preventing and treating eutrophication. Adsorption is promising but still challenged by the limited adsorption capacity at low phosphate concentrations, which leads to high costs. Herein, we propose a heterovalent metal modification strategy using Fe(II) to improve the adsorption capacity of lanthanum (La) carbonate for low-level phosphate removal. A La:Fe(II) molar ratio of 7:1 enabled the partial substitution of Fe(II) for La, resulting in a La/Fe carbonate with a high adsorption capacity. La/Fe carbonate exhibited fast adsorption kinetics, excellent applicability in a pH range of 5–7, and good reusability at low phosphate concentrations. Its adsorption capacity at low phosphate levels surpassed previously reported adsorbents. La/Fe carbonate demonstrated high resistance to complex water matrices and cost-effectiveness, achieving an effluent concentration below 0.01 mg P/L in real wastewater treatment. Mechanism analysis revealed that Fe(II) substitution led to super-saturated coordination and Fe(II) → Fe(III) conversion for charge compensation. The self-conversion of Fe(II) → Fe(III) donated electrons to neighboring La active sites, activating these active centers, which caused a positive shift in the d-band center of La active sites and enhanced interfacial electron transport between La/Fe carbonate and phosphate. This work offers an efficient, easy-to-operate, and low-cost approach to achieve ultra-low phosphate concentrations through adsorption, and fills the research gap on the mechanism of heterovalent metal modulation to enhance the phosphate adsorption capacity.

High‐Performance Synaptic Devices Based on Cross‐linked Organic Electrochemical Transistors with Dual Ion Gel

AbstractOrganic electrochemical transistors (OECTs) represent a promising approach for flexible, wearable, biomedical electronics, and sensors integrated with diverse substrates. Their ability to operate at low voltages and interact effectively with biological systems makes them particularly suitable for neuromorphic applications. For neuromorphic devices, OECTs must enhance electrical performance, biocompatibility, and signal storage/erasure capabilities. While UV cross‐linking methods with various side effects on organic semiconductors are predominant in improving mobility and current retention time, thermal cross‐linking based on the solution process has not been extensively explored. Additionally, despite significant research on the modification of electrolyte property, the ionic charge compensation mechanisms between multiple electrolytes are still unclear. This study employs a cross‐linking strategy involving the chemical reaction of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) with di‐tert‐butyl‐peroxide (DTBP) to create a cross‐linked P3HT active layer. Furthermore, a dual ion gel structure combining a conventional ion gel with a chitosan‐based ion gel is investigated for increased ionic transport to enhance OECT performance. Using the above two methods, the enhanced electrical performance showing the mobility of 25 F cm−1 V−1 s−1 and synaptic properties showing long‐term plasticity of cross‐linked OECTs with a dual ion gel structure are demonstrated, suggesting their potential application as high‐performance neuromorphic devices.

A Universal Interfacial Reconstruction Strategy Based on Converting Residual Alkali for Sodium Layered Oxide Cathodes: Marvelous Air Stability, Reversible Anion Redox, and Practical Full Cell.

Mn-based layered oxide cathodes have attracted widespread attention due to high capacity and low cost, however, poor air stability, irreversible phase transitions, and slow kinetics inhibit their practical application. Here, we propose a universal interfacial reconstruction strategy based on converting residual alkali to tunnel phase Na0.44MnO2 for addressing the above mentioned issue simultaneously, using O3 NaNi0.4Fe0.2Mn0.4O2@2 mol % Na0.44MnO2 (NaNFM@NMO) as the prototype material. The optimized material exhibits an initial capacity and energy density comparable with lithium-ion batteries. The reversible anionic redox behavior and charge compensation mechanism of NaNFM@NMO were analyzed and verified by soft X-ray absorption spectrum and in situ X-ray absorption spectrum. Due to the intrinsic stability of the tunnel structure, excellent air stability and highly reversible structure evolution of the NaNFM@NMO cathode material are achieved, which are confirmed by contact angle test, rigorous aging test, and in situ X-ray diffraction. More importantly, the NaNFM@NMO cathode demonstrates a great match with the nonpresodiated hard carbon anode and shows excellent electrochemical performance of the full cell. Additionally, such a strategy could be also applied to modify P2-type cathodes, showing superior universality and good prospects in industrialized production. Overall, the proposed strategy could improve air stability while remaining interfacial and bulk stable simultaneously and will open up a whole new field for the optimization of other electrode materials.

Entropy and Electronic Structure Modulation of a Prussian Blue Analogue Cathode with Suppressed Phase Evolution for Potassium-Ion Batteries.

Severe structural evolution and high content of [Fe(CN)6]4- defects drastically deteriorate K-ion storage performances of Prussian blue-based cathodes. Herein, a potassium manganese iron copper hexacyanoferrate (KFe2/3Mn1/6Cu1/6HCF), with suppressed anionic vacancies, eliminated band gap, and low K-ion diffusion barrier, is regarded as a cathode for potassium-ion batteries. The entropy stabilization effect and robust Cu-N bond induced by the inert Cu-ion with large electronegativity boost KFe2/3Mn1/6Cu1/6HCF to exhibit great phase state stability, thus inhibiting the structural transition of monoclinic ↔ cubic. Hence, KFe2/3Mn1/6Cu1/6HCF undergoes a zero-stress solid-solution reaction mechanism, where Fe and Mn serve as dual active sites for charge compensation. Consequently, KFe2/3Mn1/6Cu1/6HCF displays a high reversible capacity of 127.5 mAh·g-1 with an energy density of 469.2 Wh·kg-1 at 10 mA·g-1 and superior cyclic stability with a high retention of 90.7% over 100 cycles. A high-energy-density K-ion full battery is assembled, contributing an ultralong lifetime over 1000 cycles with a low-capacity fading rate of 0.038% per cycle.

Charge density-mediated crystallization kinetics for SSZ-13 transformed from coal fly ash-derived Al-rich analcite

Interzeolite transformation (IZT) is a powerful method for controlling the framework type, aluminum distribution, and hierarchical structures of zeolite. However, the in-depth mechanisms underlying IZT remain unexplored. In this study, we reveal a distinctive nucleation pathway and structural evolution of zeolite SSZ-13 during IZT that is different from the traditional hydrothermal synthesis methods. Utilizing two aluminum sources—al-rich zeolite analcite and aluminum sulfate—we accelerated the crystallization process with SSZ-13 seed crystals and TMAda-OH. Our findings indicate that the Al content, representing the charge density of the nucleation micro-environment, plays a critical role in shaping the framework and nucleation pathway. Nucleation occurred at the interface between analcite and the silica solution during IZT, characterized by a high-silica micro-environment with low charge density. In this environment, the precursor predominantly replicated the double six rings (D6R) of SSZ-13 seed fragments, forming double four rings (D4R) and CHA cages which resulted in a short induction period, fewer nucleation sites, and larger crystals size (∼1.5 μm). Conversely, when aluminum sulfate was mixed with silica sol, a uniform, Al-rich nucleation micro-environment with high negative charge density was established. the precursor primarily interacted with TMAda+ ions for charge compensation rather than with seed fragments. This slow interaction promoted the formation of CHA cages instead of D6R and D4R, leading to a longer induction period, increased nucleation sites, and smaller SSZ-13 crystal sizes (∼150 nm). This study elucidates how the charge density of micro-environment mediated interaction between precursors, organic structure-directing agent, and seed, providing valuable insights into the crystallization kinetics of IZT.

Lattice sulfuration enhanced sodium storage performance of Na0.9Li0.1Zn0.05Ni0.25Mn0.6O2 cathode

Introducing lattice oxygen redox for charge compensation in layered metal oxides is an effective way to develop advanced cathodes for high energy density sodium-ion batteries (SIBs). However, the asymmetry of lattice oxygen oxidation and reduction incurs oxygen release and crystal structure rearrangement, leading to poor reversibility of the charge and discharge process. Herein, a Na2S-assisted sulfuration strategy is firstly proposed to incorporate active sulfur into the crystal lattice of Na0.9Li0.1Zn0.05Ni0.25Mn0.6O2 cathode. The sulfur anions within the interior lattice participate in the redox process and enhance the integral coordination stability by mitigating undesired excessive oxygen redox, while the exterior sulfur forms a polyanionic layer to protect the particle surface against electrolyte corrosion. The incorporation of an extra redox center efficiently facilitates the increase of the discharge capacity from 159.9 to 179.2 mAh g−1 within the voltage range of 1.5–4.5 V. Moreover, the larger ionic radius of sulfur enlarges the interplanar spacing, thus facilitating Na+ ions transfer, especially at high current density. As a result, the modified cathode exhibits significantly enhanced electrochemical performance, with a capacity retention of 87 % after 100 cycles at 0.2 C and an excellent rate capability of 98.0 mAh g−1 at 10 C. Moreover, the assembled Na ion full cell based on a commercial hard carbon anode achieves an impressive capacity of 160.4 mAh g−1 at 0.1 C and could cycled steadily for over 100 cycles. The modification of layer oxides via sulfuration strategy provides a promising pathway for the structural design of novel cathodes with superior cycle performance for high-energy-density SIBs applications.

Entropic Design of Anionic Site to Improve Anionic Redox Stability in Lithium-Rich Cathode.

Cobalt-free manganese-rich layered oxide is considered one of the most promising cathode materials for next-generation lithium-ion batteries due to its high capacity and low cost. However, irreversible anionic redox (OAR) leads to serious failure problems and hinders its wide application. To solve the above problems, the entropy design strategy of anionic sites is proposed, which is more direct and relevant to the regulation of the OAR process compared to the traditional entropy design of TM sites. The entropic design improves the structural diversity and long-range disorder of the material, which effectively inhibits oxygen release and drastic structural strain, and alleviates structural degradation. After 400 cycles at 1C, the capacity and voltage decay per cycle are only 0.092 mAhg-1 and 1.36mV, respectively. The long cycle test (10C and 1000 cycles) at high current shows that the voltage and capacity decay are only 0.04 mAhg-1 and 0.66mV per cycle, respectively. Meanwhile, the rate performance at 10C reaches 175 mAhg-1. The charge compensation regulation and performance enhancement mechanism are investigated by systematic in-situ/ex-situ characterization and theoretical calculation. This research provides new ideas for the design of lithium-rich cathodes with stable OAR and high structural adaptability.

Evaluation of luminescent and thermal properties of Dy³⁺ doped tungstate phosphors for optoelectronic and thermometry applications

Novel Ca2MgWO6: xDy3+ (x = 1, 2, 3, 4, and 6 mol%) phosphors were synthesized via solid-state reaction method. The phosphor structure remained unchanged upon doping with Dy3+ ions. Phosphors were optical optimizated using 4F9/2 → 6H13/2 transition, and 3 mol% of Dy3+ was found to be optimal concentration. We investigated optical quenching mechanisms including energy transfer, cross-relaxation, charge compensation, and multipole-multipole interactions. Colorimetric analyses assessed colour coordinates, purity, and correlated colour temperature (CCT). The optimized phosphor showed a direct band gap of 3.68 eV, a refractive index of 2.24, and covalent bonding between Dy3+ and the host. It exhibited exceptional thermal stability with only 0.31 wt% loss up to 440 °C. Temperature-dependent emission spectra indicated high optical quenching temperature (498.82 K) and activation energy (0.21 eV). A multi-transition ratiometric approach confirmed suitability for non-contact thermometry and LED applications.

Elucidating the Structural Evolution of O3-type NaNi1/3Fe1/3Mn1/3O2: A Prototype Cathode for Na-Ion Battery.

Extending the depth-of-charge (DoC) of the layered oxide cathode presents an essential route to improve the competitiveness of the Na-ion battery versus the commercialized LiFePO4-based Li-ion battery (0.8 CNY/Wh). However, the DoC-dependent boundary between detrimental/irreversible structural distortion and neutral/reversible structure interconversion cannot be clearly distinguished, which is attributed to the ambiguous recognition of correlation among the complex phase transition, local covalent environment evolution, and charge compensation. Herein, to bridge the above gap, we employed O3-NaNi1/3Fe1/3Mn1/3O2 as the prototype cathode and extended the target DoC from typical Na0.4 (∼125 mAh/g, 4.0 V cutoff) to Na0.2 (∼180 mAh/g, 4.3 V cutoff). Regarding phase transition and charge compensation, the O3-to-P3 phase transition occurs before moderate Na0.4-DoC (Fe/Mn redox silence, Ni oxidation dominated), while further desodiation (start from Na0.4) induces a P-to-O slab transition, resulting in the coexistence of P3 and OP2 phases and subsequent OP2/O3 intergrowth phases at higher DoC (Na0.2), upon which the Fe3+-to-Fe4+ oxidation is activated for capacity contribution. The local covalent environment presents severer deviation at high DoC (merely 0.2 mol desodiation from Na0.4 to Na0.2), which can be attributed not only to the slab gliding induced by the P-to-O slab transition but also to the further aggravation caused by the Jahn-Teller distortion of the FeO6 octahedron. Such irreversible distortion of the local covalent environment would be accumulated and evolved/deteriorated into structural degradation during long-term cycling. Furthermore, the rate-dependent artificial regulation of redox process has been demonstrated and the doping strategy toward structural stabilization has been proposed.

Properties evaluation of electric smelting furnace slag: Viscosity and sulfide capacity under different FeO content

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO2-6wt.%MgO-10 wt%Al2O3-FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process.

Multivalent metal perovskite YbCoO3 as a novel proton-conducting electrolyte for solid oxide fuel cells

For solid oxide fuel cells, an electrolyte with good stability and high ion conductivity is highly desired but difficult to obtain. Recently, a novel hydrogenation mechanism other than water dissociation have been reported in multivalent metal-based oxides, which provide a new route to increase proton concentration as well as proton conductivity. In this computational study, we propose the multivalent metal perovskite YbCoO3 as a promising proton-conducting electrolyte due to its good thermodynamic and chemical stability, semiconductor characteristics, high-concentration proton incorporation, and low proton migration barrier. Our findings also reveal that charge compensation of the multivalent metal is crucial for the high-concentration proton incorporation. On the other hand, both the shortening of the O-O distance and the Co-H repulsion play key roles in determining the energy barrier to proton migration, where local structural deformations are responsible for facilitating intra- and inter-octahedron proton transfer in YbCoO3. Our results might assist in the development of high-performance proton-conducting electrolytes for advanced solid oxide fuel cells.

Nonlinear optical properties of La3+-Doped tellurite-zinc glasses: Impact of chemical bonding and physical properties via Raman and XPS

Understanding the connection between the local environments of lanthanum ions in tellurite glasses and their nonlinear optical (NLO) properties is essential for various technological applications. Rare earth ions can serve as probes for the local environments of the host material if the structure-property correlations are well understood. In this study, we investigated glasses with compositions 70TeO2 - (30-x)ZnO - (x)La2O3 (mol%) (x = 0, 5, 7, 9) fabricated by the melt-quenching technique. The capabilities of combined Raman and X-ray photoemission (XPS) spectroscopy were used to identify these glasses and define spectral deconvolution for distinguishing them in the formation of bridging oxygens (BO) and non-bridging oxygens (NBO). NLO properties were evaluated using open-aperture (OA) and closed-aperture (CA) Z-scan measurements with femtosecond (fs) laser pulses (∼220 fs, 750 Hz) at wavelengths ranging from 600 to 1500 nm. Raman spectra revealed a shift to higher frequencies from 731 to 746 cm−1, with increasing of La3+ ions, indicating the conversion of TeO4 polyhedra to TeO3 structural units, affecting the Te-O- Zn2+ or Te=O bonds and resulting in a variation of the polarizability. Besides the conventional analysis of oxidation state and chemical shifts of the core-level peaks, XPS spectroscopy included a careful analysis of the type oxygen bridges and metal-oxygen bond length to distinguish otherwise similar spectral contributions of different TZL glasses. Glasses with a high fraction of Zn2⁺ ions bonded with oxygen form NBO and modify the local structure of the glass network, while La³⁺ ions coordinate with oxygen atoms or interact with the lone pairs of tellurium atoms. By analyzing the correlation in different concentrations of La3+ ions, the Te-O bonds and NBO/(BO + NBO) ratio were clearly demonstrated. These findings suggest charge compensation between the Zn2⁺ and La³⁺ ions, for maintaining structural stability within the glass network. This study also reveals an enhancement of NLO properties as a function of La3+ ions concentration in TZL glasses under fs laser excitation due to resonant nonlinearity. The third-order optical nonlinearities showed an increase in the two-photon absorption coefficient (β) from 0.26 × 10−2 cm GW−1 (TZL5) to 0.62 × 10−2 cm GW−1 (TZL9), along with an increase in the nonlinear refractive index (n2) from 0.32 × 10−18 m2 W−1 to 0.65 × 10−18 m2 W−1. This enhancement is attributed to the increased number of NBOs and the high polarizability of La3+ ions. For all-optical switching (AOS) applications, two figures of merit were applied using the n2, α0, and β coefficients. The results suggest that the TZL glasses studied are potential candidates for AOS devices. Thus, this work not only elucidates the factors underlying the NLO properties but also highlights the promising potential of these glasses for use in AOS devices.

Optimizing giant dielectric performance in CCTO ceramics through Cr and Zn co-doping

The CaCu3Ti4O12 and CaCu2.95Zn0.05Ti4-xCrxO12 (x = 0, 0.05, and 0.10) ceramics were synthesized via solid-state reaction and sintered at 1110 °C for 3 h. XRD analysis confirmed that all samples maintained a single phase, free from impurities. SEM images revealed minor differences in grain size when comparing the undoped ceramic to those with co-doping. Notably, the co-doped CaCu2.95Zn0.05Ti3.95Cr0.05O12 ceramic exhibited significantly enhanced dielectric properties, including a high dielectric permittivity of 4.17 × 104 and a low loss tangent of 0.027. This ceramic also demonstrated stable dielectric permittivity with less than a 22 % variation from −60 to 90 °C, meeting the X5S and Y5S ceramic capacitor standards. In our first-principles calculations, we selected the CaCu2.95Zn0.05Ti3.95Cr0.05O12 structure because of its superior dielectric characteristics compared to the others. Our total energy calculations revealed that the Cr and Zn dopants are likely to be far apart from each other, indicating the absence of defects caused by the Zn and Cr dopants in the grains of our samples. The electrical property results indicate that the substitution of Zn2+ and Cr3+ ions into the CCTO lattice may help reduce oxygen loss during the sintering process at high temperatures. As a result, the need for charge compensation of Cu and Ti ions is diminished, leading to an increase in the grain and grain boundary resistances in the CaCu2.95Zn0.05Ti3.95Cr0.05O12 ceramic. Based on these results, the electrical conductivity of the material decreases, which contributes to a lower loss tangent value and improved temperature stability of the dielectric permittivity. The experimental and computational results indicated that the high dielectric permittivity is primarily due to the formation of an internal barrier layer capacitor, while improvements in dielectric properties may be associated with changes in intrinsic defects, which enhance the grain boundary response.

Intense Red Fluorescence From Surface Traps in BaSO4:V5+, Eu3+ and Its Applications.

BaSO4:V5+ synthesized at 1000°C in air exhibits an intense emission band peaking at 495 nm from surface traps assisted by atmospheric oxygen on excitation at 350 nm due to charge transfer from O2- to V5+ in the (VO4)3- tetrahedral complex. BaSO4:Eu synthesized under similar conditions exhibits both Eu2+ (375 nm) and Eu3+ (619 nm) fluorescence. Vanadium codoping quenches the Eu2+ fluorescence but enhances the Eu3+ fluorescence in BaSO4:V, Eu due to charge compensation. However, Eu codoping quenches the vanadium fluorescence by diffusion of vanadium into the crystal, and V2O5 also serves as a flux enhancing Eu3+ doping efficiency in BaSO4 lattice. The 619nm Eu3+ PL emission intensity in BaSO4:V5+, Eu3+ is comparable to 592nm emission from commercial (Y,Gd) BO3:Eu3+. However, V5+ emission shows strong thermal quenching, while Eu3+ emission shows little thermal quenching up to 210°C, making BaSO4:V5+, Eu3+ a promising new red phosphor for improving the color rendering of blue light-based white LED. The ratio of Eu3+ to V5+ fluorescence increases with excitation temperature (30°C°C-180°C) enabling BaSO4:V5+, Eu3+ to be used as a non-contact luminescence thermometer.