Insertion Of Cations Research Articles

Coupled Ionic-Electronic Equivalent Circuit to Describe Asymmetric Rise and Decay of Photovoltage Profile in Perovskite Solar Cells

In this research, we employed transient photo-voltage rise and decay measurements to investigate the origin of slow unsymmetrical rise and decay profiles in single and triple cation perovskite solar cells. Drastic changes in photo-voltage decay profile were observed upon insertion of Br−, Cs+ and FA+ ions into perovskite structures. In order to explain our observations, the activation energy for ionic defects was measured and an equivalent circuit model was proposed containing both electrical and ionic components. The electrical branch consists of a diode, the bulk capacitance and resistances for charge transport and recombination. In parallel we introduced an ionic branch describing the ionic response by a resistance for ionic charge transport and a capacitance describing ion accumulation at the interface to the charge transport layer. To reproduce the asymmetry of photo-voltage rise and decay, a diode with a parallel resistor is introduced leading to a belayed backflow of the accumulated ions. The results revealed that the activation energy of ionic defects became larger upon insertion of either halides or cations. There is larger amount of ionic defects in the case of MAPbI3 while the de-accumulation process of ions happens in much larger time scale in triple cation perovskite. The presence of ions at the interfaces results in band bending generating a potential barrier restraining electrons and holes from recombination; so the loss of built-in potential is delayed until de-accumulation of ionic double layer happens. Our model proposes that the loss of built-in potential depends on electrostatic potential drop, suggesting coupled electronic-ionic phenomenon in perovskite solar cells.

Understanding the phase dependent energy storage performance of MnO2 nanostructures

We demonstrate charge storage mechanisms of four kinds of MnO2 polymorphs (α, β, γ, and δ) both in micro- and nanodimensions successfully synthesized by hydrothermal and microwave irradiation techniques. We observed that layered δ-MnO2, comprised of self-assembled nanoflakes oriented in different directions, shows a significantly improved capacitive behavior. The maximum achieved specific capacitance is 518 F/g at a current density of 3 A/g in a 3M KOH electrolyte solution, exhibiting a large capacity retention of 83.95% over 2000 consecutive charge/discharge cycles at a current density of 10 A/g. State of the art Density Functional Theory (DFT) simulations have also been performed to support experimental data. The quantum capacitance presented from DFT simulations predicts that the δ phase exhibits highest quantum capacitance, whereas it is lowest for the β phase supporting the experimental trend. Also, the structural features of wide tunnel size (∼7 Å) for the δ phase facilitates favorable insertion of cations, whereas narrow tunnel size (∼1.89 Å) for the β phase restricts the diffusion of charge particles yielding poor capacitance performance.

Investigating the Structure and Dynamics of Apo‐Photosystem II

AbstractPhotosynthetic water oxidation is a model for future technologies employing solar energy to split water into hydrogen and oxygen. Natural water oxidation is carried out by a special manganese catalyst, the water‐oxidizing complex (WOC), located in photosystem II (PSII) of cyanobacteria, algae, and plants. Hence, there is great interest in the molecular structure as well as structural changes during catalytic activity and assembly/disassembly of the WOC. In particular, the light‐driven assembly during photosystem II repair under physiological conditions is poorly understood, and structural information about manganese depleted PSII (apo‐PSII) is required as a starting point for improving this understanding. Recently Zhang et al. (eLife 2017;6:e26933) showed that the cavity harboring the WOC in PSII remains largely intact upon manganese‐depletion and suggested that deprotonation of hydrogen‐bonding pairs enables the charge‐compensated insertion of the manganese cations without any major change of the cavity structure. By computational methods we have further investigated the structure of apo‐PSII and show how it can be stabilized by protons localized at the terminal carboxylate groups inside the remaining cavity. Ab‐initio molecular dynamics simulations suggest that not more than two water molecules fill the void left by manganese depletion.

DFT perspective on the selectivity and mechanism of ligand-free Heck reaction involving allylic esters and arenediazonium salts

A density functional theory (DFT) study has been carried out with respect to the cationic and neutral mechanism of ligand-free Heck-Matsuda cross-coupling reaction involving allylic esters and arenediazonium salts. Full Heck-Matsuda (HM) catalytic cycles were explored in the presence of different possible combinations of ligands based on previous mass-spectrometry studies. DFT calculations were performed to examine the olefinic substrate influences on the regioselectivity of this ligand-free Heck reaction. A multi-step mechanism was revealed for the oxidative addition of palladium (0) center to carbon-nitrogen bond of arenediazonium cation. The cationic migratory insertion pathway is favored by a chelated coordination involving the palladium center and the allylic ester. In contrast, for neutral complexes, a bidentate coordination of acetate ligand is the favored pathway. Regarding the hydride elimination step, the resulting free energy profile is quite flat, revealing that the Heck product and the hydride complex are easily formed for both cationic and neutral cycles. The reductive elimination step assisted by acetate is a very exothermic process, going through small relative reaction barriers. These results constitute new insights to a better understanding of the selectivity and the mechanism of ligand-free Heck-Matsuda reactions.

Decoupling the Role of Anion and Solvent on Mg Electrodeposition Efficiency through Interfacial Speciation Determination

Chemistries based on divalent working cations, such as Mg, are one class where significant effort is required to develop reductively and oxidatively stable electrolytes to support high efficiency metal deposition and cation insertion for practical energy storage systems beyond Li ion batteries. A growing body of literature exists describing bulk Mg(II) speciation over a range of electrolyte types providing insight into the origin of parasitic reactions that limit cell efficiency and overall performance. Bulk Mg(II) speciation can be argued to be an approximate descriptor of electrolyte stability at best, as the interfacial cation-anion-solvent coordination complex is what actually determines the consequences and efficiency of electron transfer. Limited knowledge is reported for interfacial Mg(II) coordination complexes, in part, due to limited available operando probes capable of discriminating between the coordination complexes at the electrode surface and within the bulk of the electrolyte. In this paper, we demonstrate the use of fluorescent and electron yield modes of operando x-ray absorption spectroscopy (XAS) to determine interfacial composition as a function of potential for select Mg(II)-anion-ether systems. We further conduct systematic variation in the coordination strength (e.g., donicity) and coordination diversity (e.g., mono- vs multi-dentate) of anions and ethers with respect to the divalent cation as a means of decoupling the role of anion and solvent in defining stability. Comparison of spectroscopic responses of Mg(II) with Zn(II) allow for additional modulation in anion/solvent coordination enthalpy further clarifying the roles of anion and solvent. The ability of XAS to discriminate early stage interphase formation at the anode providing chemical signatures of parasitic reaction will also be discussed. The methodology presented is equally applicable to electrolyte oxidative stability at the cathode, laying the foundation for design of electrolytes with suitable stability for practical, high energy density Mg ion batteries. This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

A Hybrid Energy Storage Mechanism of Zinc Hexacyanocobaltate-Based Metal–Organic Framework Endowing Stationary and High-Performance Lithium-Ion Storage

Lithium-ion batteries (LIBs) are considered to be theoretically promising with regard to large-scale energy storage and conversion systems. However, a significant problem is the lack of cost-efficient high-performance cathode materials for LIBs. In this study, we demonstrate a Prussian blue analog, zinc hexacyanocobaltate (ZnHCCo), as the low-cost and high-performance cathode material for LIBs. The open-framework crystal structure of ZnHCCo contributes toward reversible cation insertion and extraction along with the spontaneous valence change of hosts. Specifically, the as-prepared ZnHCCo exhibits a highly reversible capacity of 121.5 mAh g−1 at a current density of 1.25 C, a superior rate capability of 60.5 mAh g−1 at 6.25 C, and a stable cycling stability with a Coulombic efficiency of 96.5%. Therefore, the well-crystallized and low-cost ZnHCCo is expected to be a potential cathode material for LIBs used in grid-scale energy storage and conversion systems. In addition, the synthesis process of the electrode material can be readily up scaled using the earth abundant and environmentally benign precursors via a room-temperature wet-chemical method.

Charge Distribution on S and Intercluster Bond Evolution in Mo6S8 during the Electrochemical Insertion of Small Cations Studied by X-ray Absorption Spectroscopy.

Mo6S8 is regarded as a promising cathode material in rechargeable Mg batteries. Despite extensive studies, some fundamental questions are still unclarified, including the origination of the chemical stability, key factors inducing the structural evolution, and the factors determining the electrochemical reversibility. Herein Mo L2,3 and S K-edge X-ray absorption spectroscopy are utilized to uncover the underlying mechanism. Two kinds of S with different effective charge are found, indicating the nonuniform charge distribution. With one cation inserted, the charge distribution becomes homogeneous, relevant to the chemical stability and electrochemical reversibility. The structural evolution is attributed to the change of bond length induced by the delocalization of inserted cations. Moreover, the evolution of intercluster Mo-Mo bond length can be revealed by the drastic change of the S K pre-edge and is closely related to the electrochemical reversibility. This study can shed light on the aforementioned questions and guide the development of Mg cathode material.

Mechanism for Copper(II)-Mediated Disaggregation of a Porphyrin J-Aggregate.

J-aggregates of anionic meso-tetrakis(4-sulfonatophenyl)porphyrin form at intermediate pH (2.3–3.1) in the presence of NiSO4 or ZnSO4 (ionic strength, I.S. = 3.2 M). These aggregates convert to monomeric porphyrin units via metallation with copper(II) ions. The kinetics for the disassembly process, as monitored by UV/vis spectroscopy, exhibits zeroth-order behavior. The observed zeroth-order rate constants show a two-term dependence on copper(II) ion concentrations: linear and second order. Also observed is an inverse dependence on hydrogen ion concentration. Activation parameters have been determined for the disassembly process leading to ΔH≠ = (+163 ± 15) kJ·mol–1 and ΔS≠ = (+136 ± 11) J·K–1. A mechanism is proposed in which copper(II) cation is in pre-equilibrium with a reactive site at the rim of the J-aggregate. An intermediate copper species is thus formed that eventually leads to the final metallated porphyrin either through an assisted attack of a second metal ion or through a direct insertion of the metal cation into the macrocycle core.

The effect of CaO on the partitioning behavior of REE, Y and Sc between olivine and melt: Implications for basalt-carbonate interaction processes

The partitioning of REE,Y and Sc (R3+) between olivine and melt has been investigated experimentally during basalt-carbonate interaction. Three synthetic basalts (meltMg#72, meltMg#75 and meltMg#78) were doped with 0, 10 and 20 wt% CaCO3 and then equilibrated for 72 h at 1 atm, 1,150, 1,200 and 1,250 °C, and the QFM oxygen buffer. The thermal decomposition of CaCO3 produced CaO contents in the melt up to ~22 wt%. Regular relationships are found between the ionic radius and the partition coefficient (DR3+), showing typical near-parabolic patterns. DR3+ is weakly dependent on temperature, but decreases with increasing CaCO3 in the starting material (e.g., DSc decreases from 0.20 to 0.13). From the point of view of the lattice strain theory, DR3+ is described in terms of the radius of the crystal site (r0), the Young Modulus (E) due to the elastic response of that site to lattice strain caused by cation insertion, and the strain-free partition coefficient (D03+). The value of r0 decreases as Ca cations are accommodated into the more distorted M2 site of olivine via progressive CaFe substitutions. This mechanism is accompanied by a higher proportion of Mg cations entering into the smaller M1 site, making the optimum ionic radius smaller and favoring the crystallization of more forsteritic olivines from decarbonated melts. The enrichment of Ca in the crystal lattice is also proportional to the number of Si and Ca cations available in the melt. This causes E to be anticorrelated either with Ca in olivine or the activity of CaO in the melt. R3+ cations behave as network modifiers and, during basalt-carbonate interaction, the increasing abundance of non-bridging oxygens enhances the solubility of REE, Y and Sc in the melt. As a consequence, D03+ is negatively correlated with the degree of melt depolymerization. Additionally, the strain of the crystal lattice dominates the DR3+ parabolic patterns and D03+ is strongly controlled by forsterite and aluminium concentrations in olivine. The accommodation of REE, Y and Sc in the crystal lattice requires maintenance of local charge-balance by the generation of vacancies, in accord with a paired substitution of R3+ and a vacancy for Mg in octahedral sites.

Evolving spin periodicity and lock-in transition in the frustrated ordered ilmenite-type β−Mn2InSbO6

Polar magnets are promising materials for applications such as multiferroics or in spintronics. In double-corundum-related oxides, the cation ordering imposes a polar structure and the use of high pressure facilitates the insertion of magnetic cations into the compounds. Here we present the high-pressure synthesis of a polar and ferrimagnetic corundum derivative of ${\mathrm{Mn}}_{2}{\mathrm{InSbO}}_{6}$, which adopts the ordered-ilmenite-type structure. Neutron powder diffraction reveals that the high-temperature nearly collinear ferrimagnetic phase evolves to an incommensurate helical structure with ${k}_{\ensuremath{\delta}}=[0\phantom{\rule{0.28em}{0ex}}0\phantom{\rule{0.28em}{0ex}}{k}_{z}]$ propagation vector, which then locks to the commensurate value of ${k}_{z}=1/8$. This complex magnetic behavior is likely to be related to magnetic frustration and the polar nature of the ordered double-corundum structure.

Self-Healing Lamellar Structure Boosts Highly Stable Zinc-Storage Property of Bilayered Vanadium Oxides

Rechargeable aqueous zinc-ion batteries have been considered one of the promising alternative energy-storage systems to lithium ion-batteries owing to their low cost and high safety. However, there is lack of long-life positive materials, which severely restricts the development of zinc-ion batteries. The strong interactions present between the intercalated multivalent cations and host materials inevitably cause structural distortions and create large migration barriers for the diffusion of cations, resulting in poor cycling stability and limited rate performance. Here, we report the application of bilayered ammonium vanadium oxide (NH4V4O10) as the cathode material for zinc-ion batteries. A self-healing lamellar structure, which combines a macroscopically reversible morphological transformation and a microscopically adjustable interlayer spacing to accommodate the strong interactions, is observed upon insertion and release of cations. This stable architecture enables a specific capacity of 147 mA h g-1 at a current density of 200 mA g-1 (voltage window: 1.7-0.8 V vs Zn2+/Zn) and a capacity retention of more than 70.3% over 5000 cycles (5000 mA g-1). Our finding provides a new alternative for zinc-ion batteries and inspiration for how to further develop advanced positive electrodes by employing materials with flexible microarchitectures.

Electro-chemo-mechanical effects of lithium incorporation in zirconium oxide

Understanding the response of functional oxides to extrinsic ion insertion is important for technological applications including electrochemical energy storage and conversion, corrosion, and electronic materials in neuromorphic computing devices. Decoupling the complicated chemical and mechanical effects of ion insertion is difficult experimentally. In this work, we assessed the effect of lithium incorporation in zirconium oxide as a model system, by performing first-principles based calculations. The chemical effect of lithium is to change the equilibria of charged defects. Lithium exists in $\mathrm{Zr}{\mathrm{O}}_{2}$ as a positively charged interstitial defect, and raises the concentration of free electrons, negatively charged oxygen interstitials, and zirconium vacancies. As a result, oxygen diffusion becomes faster by five orders of magnitude, and the total electronic conduction increases by up to five orders of magnitude in the low oxygen partial pressure regime. In the context of Zr metal oxidation, this effect accelerates oxide growth kinetics. In the context of electronic materials, it has implications for resistance modulations via ion incorporation. The mechanical effect of lithium is in changing the volume and equilibrium phase of the oxide. Lithium interstitials together with zirconium vacancies shrink the volume of the oxide matrix, release the compressive stress that is needed for stabilizing the tetragonal phase $\mathrm{Zr}{\mathrm{O}}_{2}$ at low temperature, and promote tetragonal-to-monoclinic phase transformation. By identifying these factors, we are able to mechanistically interpret experimental results in the literature for zirconium alloy corrosion in different alkali-metal hydroxide solutions. These results provide a mechanistic and quantitative understanding of lithium-accelerated corrosion of zirconium alloy, as well as, and more broadly, show the importance of considering coupled electro-chemo-mechanical effects of cation insertion in functional oxides.

Concentration-Mediated Band Gap Reduction of Bi2MoO6 Photoanodes Prepared by Bi3+ Cation Insertions into Anodized MoO3 Thin Films: Structural, Optical, and Photoelectrochemical Properties

A secondary cation insertion technique to fabricate ternary Bi2MoO6 thin films with reduced optical band gaps and shallow valence bands by the controllable insertion of Bi3+ cations into anodized MoO3 thin films has been established. Near-complete conversion of the MoO3 thin film to a low-temperature-phase γ(L)-Bi2MoO6 thin film was achieved when the MoO3 thin films were subject to hydrothermal treatment in a low Bi(NO3)3·5H2O solution concentration. In contrast, a bilayered Bi2MoO6/MoO3 thin film photoelectrode comprising predominantly a high-temperature-phase γ(H)-Bi2MoO6 oxide–electrolyte interface top region and a MoO3 oxide–collector interface bottom region was formed when a high Bi(NO3)3·5H2O solution concentration was utilized. UV–vis spectroscopy shows both the γ(L)-Bi2MoO6 (Eg = 2.7 eV) and γ(H)-Bi2MoO6 (Eg = 3.05 eV) thin films exhibit smaller band gaps than MoO3 (Eg = 3.4 eV). For γ(L)-Bi2MoO6, the reduction in optical band gap was attributed to the formation of a higher-lying O 2p valence band maximum while, for the γ(H)-Bi2MoO6 thin film, hybridization of the Bi 6s orbitals with the O 2p valence orbitals lowers the potential of the valence band maximum, leading to the reduced band gap. Overall, the Bi2MoO6 thin films with the highest γ(L)-Bi2MoO6 concentration exhibited the highest photocurrent density. The photocurrent enhancement can be attributed to two main reasons: first, the trilayer Bi2MoO6/MoO3 heterostructure obtained from the direct thin film assembly enables a smooth percolation of photoexcited charges from the surface generation sites to the charge collection sites at the Mo substrate, minimizing charge recombination losses; second, the MoO6 octahedra-coordinated γ(L)-Bi2MoO6 possesses a wide conduction band enabling fast separation and migration of delocalized charges. The secondary cation insertion technique has potential as a universal method to prepare complex oxides with narrow band gaps and shallow valence bands from insertion-type oxides for solar energy applications.

Interlayer-Spacing-Regulated VOPO4 Nanosheets with Fast Kinetics for High-Capacity and Durable Rechargeable Magnesium Batteries.

Owing to the low-cost, safety, dendrite-free formation, and two-electron redox properties of magnesium (Mg), rechargeable Mg batteries are considered as promising next-generation secondary batteries with high specific capacity and energy density. However, the clumsy Mg2+ with high polarity inclines to sluggish Mg insertion/deinsertion, leading to inadequate reversible capacity and rate performance. Herein, 2D VOPO4 nanosheets with expanded interlayer spacing (1.42 nm) are prepared and applied in rechargeable magnesium batteries for the first time. The interlayer expansion provides enough diffusion space for fast kinetics of MgCl+ ion flux with low polarization. Benefiting from the structural configuration, the Mg battery exhibits a remarkable reversible capacity of 310 mAh g-1 at 50 mA g-1 , excellent rate capability, and good cycling stability (192 mAh g-1 at 100 mA g-1 even after 500 cycles). In addition, density functional theory (DFT) computations are conducted to understand the electrode behavior with decreased MgCl+ migration energy barrier compared with Mg2+ . This approach, based on the regulation of interlayer distance to control cation insertion, represents a promising guideline for electrode material design on the development of advanced secondary multivalent-ion batteries.

Direct Assessment of Nanoconfined Water in 2D Ti3C2 Electrode Interspaces by a Surface Acoustic Technique.

Although significant progress has been achieved in understanding of ion-exchange mechanisms in the new family of 2D transition metal carbides and nitrides known as MXenes, direct gravimetric assessment of water insertion into the MXene interlayer spaces and mesopores has not been reported so far. Concurrently, the latest research on MXene and Birnessite electrodes shows that nanoconfined water dramatically improves their gravimetric capacity and rate capability. Hence, quantification of the amount of confined water in solvated electrodes is becoming an important goal of energy-related research. Using the recently developed and highly sensitive method of in situ hydrodynamic spectroscopy (based on surface-acoustic probing of solvated interfaces), we provide clear evidence that typical cosmotropic cations (Li+, Mg2+, and Al3+) are inserted into the MXene interspaces in their partially hydrated form, in contrast to the insertion of chaotropic cations (Cs+ and TEA+), which effectively dehydrate the MXene. These new findings provide important information about the charge-storage mechanisms in layered materials by direct quantification and efficient control (management) over the amount of confined fluid in a variety of solvated battery/supercapacitor electrodes. We believe that the proposed monitoring of water content as a function of the nature of ions can be equally applied to solvated biointerfaces, such as the ion channels of membrane proteins.

Experimental study on property and electrochromic function of stacked WO3/Ta2O5/NiO films by sputtering

Both WO3 and NiO are known to be electrochromic materials. In this study, a stack of PET/IZO/WO3/Ta2O5/NiO/IZO electrochromic device (IZO: indium zinc oxide) was fabricated on polymeric substrate (polyethylene terephthalate, PET) by sputtering. Before stacking all layers, each material was separately deposited on a glass substrate under different oxygen flow rates and examined for their microstructures, compositions, optical properties and electrochromic functions. The selected oxygen flow rates have all deposited films to be amorphous except NiO with some crystallites. The electrochromism of WO3 and NiO was materialized by electrochemical insertion of cations (Li+) and electrons into WO3 and NiO films before subjected to potential statics and cyclic voltammetry. The coloration efficiency and transparency of films from these electrochemical tests were evaluated by UV–Vis-NIR spectroscopy. It was found that electrochromism is feasible between ±1 V with efficiency reaching 60 cm2/C in WO3 and 20 cm2/C in NiO, and optical transmittance between 65% - 80% in the range of visible light for films deposited under specific conditions. By analyzing and comparing the coloration efficiency and transparency from electrochemical tests, we can determined a feasible set of process parameters, i.e. oxygen flow rates for sputtering. These parameters then were used to fabricate the stack of PET/IZO/WO3/Ta2O5/NiO/IZO and its electrochromic function was successfully demonstrated.

Multielectron‐Transfer‐based Rechargeable Energy Storage of Two‐Dimensional Coordination Frameworks with Non‐Innocent Ligands

The metallically conductive bis(diimino)nickel framework (NiDI), an emerging class of metal-organic framework (MOF) analogues consisting of two-dimensional (2D) coordination networks, was found to have an energy storage principle that uses both cation and anion insertion. This principle gives high energy led by a multielectron transfer reaction: Its specific capacity is one of the highest among MOF-based cathode materials in rechargeable energy storage devices, with stable cycling performance up to 300 cycles. This mechanism was studied by a wide spectrum of electrochemical techniques combined with density-functional calculations. This work shows that a rationally designed material system of conductive 2D coordination networks can be promising electrode materials for many types of energy devices.

Multielectron‐Transfer‐based Rechargeable Energy Storage of Two‐Dimensional Coordination Frameworks with Non‐Innocent Ligands

AbstractThe metallically conductive bis(diimino)nickel framework (NiDI), an emerging class of metal–organic framework (MOF) analogues consisting of two‐dimensional (2D) coordination networks, was found to have an energy storage principle that uses both cation and anion insertion. This principle gives high energy led by a multielectron transfer reaction: Its specific capacity is one of the highest among MOF‐based cathode materials in rechargeable energy storage devices, with stable cycling performance up to 300 cycles. This mechanism was studied by a wide spectrum of electrochemical techniques combined with density‐functional calculations. This work shows that a rationally designed material system of conductive 2D coordination networks can be promising electrode materials for many types of energy devices.

Structural, magnetic and optical properties of nanosized Ni0.4Cu0.2Zn0.4R0.05Fe1.95O4 (R = Eu3+, Sm3+, Gd3+ and Pr3+) ferrites synthesized by co-precipitation method with ultrasound irradiation

Doped spinel ferrites (Ni0.4Cu0.2Zn0.4R0.05Fe1.95O4 (R = Eu3+, Sm3+, Gd3+ and Pr3+) were synthesized via co-precipitation method with ultrasound irradiation for 2 h at T = 90 °C and dissipated power Pdiss = 46.27 W. The prepared samples were characterized by different techniques: X-ray diffraction (XRD), Energy-Dispersive Spectrometry (EDS), Fourier transform spectroscopy (FTIR), vibrating sample magnetometry (VSM) and photoluminescence (PL) emissions. The experimental results show that co-precipitation method coupled with ultrasound irradiation can lower the crystallite size (15–18 nm) and favors in getting a single spinel phase. Analysis of EDS and FTIR spectra indicates the fruitful insertion of the rare earth cations into ferrite lattice. The saturation magnetization (Ms) measured using VSM at room temperature increases with increasing ionic radius (Eu3+ ≥ Gd3+ > Sm3+ > Pr3+). The photoluminescence properties of these samples are investigated using 240 nm excitation wavelength radiation sources. No changes in PL peaks positions are noted for all samples except their intensities during the experimental analysis.

Correlated Metal SrVO3 Based All-Solid-State Redox Transistors Achieved by Li+ or H+ Transport

Two SrVO3 (SVO)-based all-solid-state redox transistors were fabricated; one with a Li4SiO4 (LSO) Li+ ion conductor and one with Y-stabilized-ZrO2 (YSZ) H+ ion conductor. The two devices showed different electronic conduction characteristic that were in contrast to that expected with similar electronic carrier doping behavior due to monovalent cation insertion. While the YSZ device showed a relatively large drain current enhancement (9%), that shown by the LSO device was very small (0.2%). In both devices, the electrical conduction characteristic was accompanied by considerable hysteresis due to non-steady state ionic diffusion in the SVO thin film. Furthermore, the gate current value was much larger than present in electric-double-layer-transistors (EDLT), indicating that these are redox transistors rather than EDLT.