Ionic Polarization Research Articles

Spontaneous out-of-plane ionic polarization and improved carrier characteristics in two-dimensional perovskite oxides: A case study of CdTiO3/PbTiO3 and CdTiO3/SrTiO3 heterostructures

Two-dimensional (2D) perovskite oxides are a new member of the low-dimensional material family, with many potential properties to be explored. By using first-principles calculations, we studied two types of perovskite heterostructures (CdTiO3/PbTiO3 and CdTiO3/SrTiO3) to understand their novel properties and explore ways to expand their functionalities. It was found that these heterostructures can exhibit controllable bandgaps, high carrier mobility and high surface charge concentration, demonstrating good potential for applications in photovoltaic and catalytic fields. Moreover, a spontaneous out-of-plane ionic polarization occurs in CdTiO3/PbTiO3 heterostructure, which makes it possible to couple its properties with external electric field, strain, etc., thus increasing the ways to regulate the system properties. Our findings are beneficial to the development and optimization of advanced 2D materials based on perovskite structures.

A New Method for Investigating the Ionic Polarization of Ferroelectric Materials

A New Method for Investigating the Ionic Polarization of Ferroelectric Materials

Application of Metal Oxide in Litho-Vanadium Glasses Containing Non-Magnetic Metal Ions: Physical and Optical Properties Analysis

Sodium-modified litho-vanadium glasses containing non-magnetic Aluminium ions of composition 50Li2CO3 - (30-X) Na2 CO3- 20V2O5 -xAl2O3 (30 ≤ x ≥ 5) (LNVA) glasses were prepared by melt quenching technique. The density of the glass samples was measured and found to increase with the Aluminium content of the glass matrix. The measured values of refractive index and polaron radius of the glass network show opposite behaviour with an increase of Aluminium content. Through band gap energy and refractive index, Oxide ion polarizability and electronic polarizability were determined by using the Lorentz-Lorenz equation. The value of Oxide ion polarizability and electronic polarizability is found to be decreased with decreasing band gap energy and increasing refractive index. The value of optical basicity was measured using electronic polarizability and is found to be decreased with decreasing inter-nuclear distance. The band gap energy values of the glass network were found to decrease from 3.241 to 2.134 eV. The metallisation criterion of the glass material was calculated and found to decrease with Aluminium content.

Effect of zirconium oxide nanoparticles on thermal, optical, and radiation shielding properties of Bi2O3-B2O3-MnO2 glasses

This study has explored the DSC, UV–Vis absorption spectroscopy, gamma ray and neutron shielding properties of Bi2O3-B2O3-MnO2: ZrO2 glasses. It demonstrates a unique approach to photon shielding analysis using JENDL/PD-2016 photonuclear data and employs a validated spherical neutron model for neutron shielding. Five transparent glasses were prepared with the chemical composition (in mol%) of 29Bi2O3-70B2O3-(1-x)MnO2: xZrO2, and labeled as MZ0.00 (for x = 0), MZ0.25 (for x = 0.25), MZ0.50 (for x = 0.5), MZ0.75 (for x = 0.75) and MZ1.00 (for x = 1). The glass ceramic nature of the samples has been characterized by DTA thermograms. The glass forming ability parameters (Kgl, S & H) were found to be highest for the sample MZ1.00. The UV–Visible optical absorption spectra have been interpreted, and hence the cut-off wavelength (λcut-off) and optical band gap (Eo) were evaluated. The absorption spectra have revealed the co-existence of manganese ions in three stable valence states Mn4+, Mn3+ and Mn2+ in the samples. When ZrO2 nanoparticles were added in the composition up to x = 0.50 mol%, the red shift in the cut-off wavelength (λcut-off) with gradual shrinkage in optical band gap (Eo) has been observed. Also, the linear and non-linear optical parameters viz., refractive index (no), non-linear refractive index (n2), linear optical susceptibility (χ(1)) and non-linear optical susceptibility (χ(3)) have been evaluated. These parameters showcased that B-O, Bi-O, Mn-O, Zr-O, etc. bonds could be strengthened by subsequent reduction of polarization of the trivalent ions (B3+ ions, Bi3+ ions and Mn3+ ions) in the glass system at higher concentrations of ZrO2. Photoatomic and photonuclear attenuation studies portrayed that the sample MZ0.50 has the lowest photon shielding capability. The fast neutron effective removal cross section (ΣR) was observed to be the highest for the sample MZ1.00. Thus, these glasses can be used to design the thermally stable transparent glasses, tunable optical elements, and radiation shielding materials.

Effect of Gd[formula omitted]O[formula omitted] on physical, structural, optical and magnetic characteristics of vanadium containing borosilicate glasses

This study reports the effect of Gd2O3 on physical, structural, optical, and magnetic properties of 40SiO2−40B2O3−10V2O5−(10−x)Fe2O3−xGd2O3 (x = 2, 4, and 6 mol%) glasses. The structural, optical, and magnetic characteristics of the as-quenched samples were obtained using various experimental techniques. The optical band gap was decreased with the concentration of Gd2O3 in place of Fe2O3 in glass composition i.e., 4.03 to 3.81 eV whereas, the theoretical optical basicity and oxide ion polarizability increase. The magnetic nature of the as-prepared glasses is soft and exhibited saturation magnetization in the range of 2.1 to 2.6 emu/g with a critical magnetic field of 122 to 138 Oe. With a higher critical magnetic field, the inclusion of Gd2O3 reduces saturation magnetization. This phenomenon could be related to the change in local structure due to glass network modification by Gd2O3 and the presence of some nanocrystalline or microcrystalline phase in a glass matrix. The developed glass has the potential to be used as a thermoseed for treating cancer patients with hyperthermia.

Polarizabilities of the negative ions of hydrogen and positronium in nonideal classical plasmas

We investigate the polarizability of the negative ions of hydrogen and positronium embedded in nonideal classical plasmas using correlated exponential wavefunctions. The interactions among the charged particles in plasmas have been taken care of by a pseudopotential, derived from a solution of Bogolyubov's hierarchy equations. The effects of nonideality of plasma on the ground state energies and the static and dynamic dipole polarizabilities of the negative ions have been studied in detail for wide range of nonideality. The results show interesting features.

Mn–Si synergistically co-doping adjusting microstructures and microwave-millimeter-wave dielectric properties of Y3Al5O12 garnet ceramics: Lattice occupancy and ligand distortion perspective

Y3-xMnxAl5-xSixO12 (x = 0.1–0.5) ceramics were fabricated through the high-temperature reaction method. The effects of Mn2+-Si4+ co-doping on lattice occupancy, ligand distortion and microwave dielectric properties of Y3Al5O12 garnet were inquired. Mn2+ ions successively occupy the lattice sites of Y3+ dodecahedron and Al3+ octahedron along with the increase of distortion degree of [AlO6] octahedron. In Y3-xMnxAl5-xSixO12, εr predominantly correlates with ionic polarizability, average bond ionicity (△fi) and Mn2+ ionic lattice occupation. The Q × f is primarily influenced by factors like relative density, lattice energy (U) and atomic packing fraction. Meanwhile, τf is associated with the distortion of octahedra, bond energy (E), and the bond valence between Y/Mn and O. Ultimately, the microwave and millimeter-wave dielectric properties of the Y2.8Mn0.2Al4.8Si0.2O12 ceramics excel with values of εr = 10.89, Q × f = 56,135 GHz@11 GHz (Q × f = 88200 GHz@25 GHz), and τf = -39.35 ppm/°C.

Ion-combination specific effects driving the enzymatic activity of halophilic alcohol dehydrogenase 2 from Haloferax volcanii in aqueous ionic liquid solvent mixtures.

Biocatalysis in ionic liquids enables novel routes for bioprocessing. Enzymes derived from extremophiles promise greater stability and activity under ionic liquid (IL) influence. Here, we probe the enzyme alcohol dehydrogenase 2 from the halophilic archaeon Haloferax volcanii in thirteen different ion combinations for relative activity and analyse the results against molecular dynamics (MD) simulations of the same IL systems. We probe the ionic liquid property space based on ion polarizability and molecular electrostatic potential. Using the radial distribution functions, survival probabilities and spatial distribution functions of ions, we show that cooperative ion-ion interactions determine ion-protein interactions, and specifically, strong ion-ion interactions equate to higher enzymatic activity if neither of the ions interact strongly with the protein surface. We further demonstrate a tendency for cations interacting with the protein surface to be least detrimental to enzymatic activity if they show a low polarizability when combined with small hydrophilic anions. We also find that the IL ion influence is not mitigated by the surplus of negatively charged residues of the halophilic enzyme. This is shown by free energy landscape analysis in root mean square deviation and distance variation plots of active site gating residues (Trp43 and His273) demonstrating no protection of specific structural elements relevant to preserving enzymatic activity. On the other hand, we observe a general effect across all IL systems that a tight binding of water at acidic residues is preferentially interrupted at these residues through the increased presence of potassium ions. Overall, this study demonstrates a co-ion interaction dependent influence on allosteric surface residues controlling the active/inactive conformation of halophilic alcohol dehydrogenase 2 and the necessity to engineer ionic liquid systems for enzymes that rely on the integrity of functional surface residues regardless of their halophilicity or thermophilicity for use in bioprocessing.

Mechanisms for optimizing the dielectric properties of spinel Li10ZnTi13O32 ceramics by Na+ doping

Herein, the dielectric properties of Na + doped Li10ZnTi13O32 ceramics were investigated by first-principles computational prediction and combined with the solid-phase reaction method. Li9.88Na0.12ZnTi13O32 obtained the best dielectric properties by sintering at 1050 °C for 4 h: εr = 30.01, Q × f = 90,879 GHz (@7.8 GHz), τf = 3.93 ppm/°C. In terms of extrinsic factors, the optimization of the densification, the creation of the second phase TiO2, and the increase of the grain size resulted in better dielectric properties. Intrinsic factors indicate that the weakening of the damping behavior and the increase in the electron cloud density lead to a decrease in the dielectric loss. The increase in ion polarisation and the blue shift of the Raman wavenumber lead to a gradual increase in εr. The temperature stability is optimized depending on the TiO2 content. The optimized Li9.88Na0.12ZnTi13O32 ceramics have unlimited applications in microwave communications.

Microstructured optical fiber sensor for detection of temperature-dependent light-induced ionic liquid molecular polarizability

Microstructured optical fiber sensor for detection of temperature-dependent light-induced ionic liquid molecular polarizability

Re2TiO5: Special dielectric titanates exhibiting abnormally low permittivity and a positive coefficient of resonance frequency

AbstractIn this study, a series of rare‐earth titanates with the general formula Re2TiO5 (Re = Er, Tm, Yb, and Lu) were synthesized and their microwave dielectric properties were reported. The impact of differences in rare‐earth cation radii on the structure and dielectric properties was systematically analyzed. The findings indicated that ceramics of Re2TiO5 (Re = Er, Tm, Yb, and Lu) were crystallized into a cubic structure with space group Fd‐3m, as confirmed by Rietveld refinement and selected‐area electron diffraction patterns. The rare‐earth elements were analyzed for their impact on microwave dielectric properties, considering factors such as ionic polarizability, packing fraction, and bond valence theory. The resulting materials exhibited excellent microwave dielectric properties with a low permittivity (6.95–7.21), high‐quality factors (19 451–20 115 GHz), and low positive temperature coefficient of resonance frequency (19.34–20.90 ppm/°C). The origin of low permittivity was elucidated through the analysis of bond length, X‐ray photoelectron spectroscopy, and impedance spectroscopy. This series of titanates exhibited unusually low permittivity characteristics in the microwave frequency range, which could meet the low signal transmission delay requirements in wireless communication.

Interplay Between Electron Correlations, Magnetic State, and Structural Confinement in LaNiO<sub>3</sub> Ultrathin Films

We report a theoretical study of the effects of electron correlations and structural confinement on the electronic properties and magnetic state of LaNiO3(LNO) thin films epitaxially deposited on the(001)LaAlO3(LAO) substrate. Using the DFT + U method we compute the electronic band structure, magnetic properties, and phase stability of the 1.5 unit-cell-thick NiO2-terminated LNO thin films. Our results reveal complex diversity of the electronic states caused by the effects of structural confinement, interfacial charge transfer and electronic correlations. Our calculations suggest the appearance of in-plane (110) charge disproportionation of the Ni ions in the interface NiO2layer of the antiferromagnetically ordered LNO thin films. Moreover, the electronic states of both the antiferromagnetic and ferromagnetic LNO/LAO show a large orbital polarization of the Ni ions in the surface NiO2layers. Our results suggest the crucial importance of oxygen defects to explain the metal-to-insulator phase transition experimentally observed in a few-unit-cell-thick LNO/LAO thin films.

Eliminating concentration polarization with gradient lithiophilic sites towards high performance lithium metal anodes under low N/P ratio

Three-dimensional (3D) skeletons have been extensively explored for effectively inhibiting dendrite growth and mitigating the volume change of lithium (Li). However, the ionic concentration polarization ascribing to the different ionic transmission distance in 3D skeletons inevitably induce the uneven growth of Li, leading to preferential deposition of Li in the top region rather than a spatially ordered manner from bottom-up. This uncontrollable deposition will deviate the original guidance of 3D skeleton. In this study, a gradient lithiophilic carbon fibers (CFs) is designed and constructed by regulating the distribution of ZnO nucleation sites (CFs@GZnO skeleton) to achieve a spatially ordered Li plating/stripping process. Additionally, the top lithiophobic CFs layer acts as a buffer layer to accommodate inactive Li, avoiding the block of Li+ inward migration, the middle and bottom CFs layer decorated with different amounts of lithiophilic ZnO nucleation sites enable lithium preferentially deposits in the bottom layer and further supporting the sequential bottom-up depositing process. Benefiting from this gradient lithiophilic design, the non-uniform ionic polarization within the 3D skeleton is mitigated, effectively inducing Li plating/stripping in a controllable spatially ordered manner and suppressing the volume variation. Full cell with an ultrahigh mass loading NCM811 cathode (38 mg cm−2) and Li-CFs@GZnO (CFs@GZnO skeleton pre-plated with Li) anode under a low negative to positive N/P ratio of 2 achieved a lifespan of 100 cycles with a capacity fading of only 0.083 % per cycle and an average CE of 99.7 %. Thus, the strategy of inducing gradient lithiophilic sites into 3D skeletons may provide a new avenue to construct a dendrite-free and stable metal anode for high energy density LMBs.

Crystal structure, lattice energy and microwave dielectric properties of melilite-type Ba1-xSrxCu2Ge2O7 ceramics

The Ba1-xSrxCu2Ge2O7 was successfully obtained through the solid-state reaction method, with single-phase BaCu2Ge2O7 formed at 850 °C. Scanning electron microscopy analysis revealed the excellent chemical compatibility of Ba1-xSrxCu2Ge2O7 with silver. The properties of Ba1-xSrxCu2Ge2O7 ceramics were explained using the P-V-L theory. The εr-corr decreased with the polarization rate (Σχu*Nbu) and ion polarization of the unit cell. The Q×f increased with the chemical bond strength and lattice energy (Ucal), particularly the lattice energy of the Ge-O bond (U(Ge-O)). The τf exhibited an opposite trend to the Q×f value and was influenced by the U(Cu-O) and susceptibility of the Cu-O bond (χ(Cu-O)). Sintering at 875 °C for 3 h yielded optimal microwave dielectric performance for Ba1-xSrxCu2Ge2O7 ceramics, with observed values of εr = 9.26 ± 0.14, Q×f = 85,660 ± 4200 GHz, and τf = −15.6 ± 1.1 ppm/°C at x = 0.10. These promising microwave dielectric properties make Ba1-xSrxCu2Ge2O7 a potential candidate for LTCC material applications.

Boosting the Performance of Photomultiplication-Type Organic Photodiodes by Embedding CsPbBr3 Perovskite Nanocrystals.

In this study, it is demonstrated that CsPbBr3 perovskite nanocrystals (NCs) can enhance the overall performances of photomultiplication-type organic photodiodes (PM-OPDs). The proposed approach enables the ionic-polarizable CsPbBr3 NCs to be evenly distributed throughout the depletion region of Schottky junction interface, allowing the entire trapped electrons within the depletion region to be stabilized, in contrast to previously reported interface-limited strategies. The optimized CsPbBr3 -NC-embedded poly(3-hexylthiophene-diyl)-based PM-OPDs exhibit exceptionally high external quantum efficiency, specific detectivity, and gain-bandwidth product of 2,840,000%, 3.97×1015 Jones, and 2.14×107 Hz, respectively. 2D grazing-incidence X-ray diffraction analyses and drift-diffusion simulations combined with temperature-dependent J-V characteristic analyses are conducted to investigate the physics behind the success of CsPbBr3 -NC-embedded PM-OPDs. The results show that the electrostatic interactions generated by the ionic polarization of NCs effectively stabilize the trapped electrons throughout the entire volume of the photoactive layer, thereby successfully increasing the effective energy depth of the trap states and allowing efficient PM mechanisms. This study demonstrates how a hybrid-photoactive-layer approach can further enhance PM-OPD when the functionality of inorganic inclusions meets the requirements of the target device.

Structure characteristics and microwave/terahertz dielectric response of low-permittivity (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr3(MoO4)9 high-entropy ceramics

Microwave dielectric ceramics play a vital role in wireless communication systems. However, it is a great challenge to obtain ideal performances of single-phase ceramics. In this work, (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr3(MoO4)9 (abbreviated as L5ZMO) high-entropy ceramics were successfully prepared by the solid-state reaction method, the pure trigonal L5ZMO structure can be synthesized in the mixture calcined at 700 °C. Rietveld refinement based on XRD data reveals that lattice parameters of L5ZMO ceramics are affected by the radius of the five rare earth elements, which indicates that the rare earth elements have been solubilized and randomly distributed in the Ln-site. The relative density illustrates a strong dependence on sintering temperature, which gradually increases with increasing sintering temperature. Based on the analysis of bond characteristics, the Mo–O bond exhibits a vital effect on the dielectric properties of L5ZMO ceramics. Besides, the infrared reflection spectrum and terahertz time-domain spectroscopy analysis show that ionic polarization is the dominant polarization in the microwave/terahertz bands. Meanwhile, the tan δ can be further reduced by optimizing process parameters. Notably, the L5ZMO high-entropy ceramics sintered at 750 °C exhibit outstanding dielectric properties of εr = 10.46, Q·f = 59,713 GHz, and τf = −21.94 ppm/°C, indicating that the high-entropy design optimizes τf (−38.8 ppm/°C) of the simple La2Zr3(MoO4)9 ceramics. The attempt provides theoretical guidance for the application of high-entropy design concepts in microwave/terahertz bands.

Structural criticality manifested by a polarized ionic layer on a MWCNT yarn surface under mechanical loading

The electrochemical capacitance of an energy harvester based on a multiwalled carbon-nanotube yarn is proportional to the total strain and then rapidly decreases after the strain exceeds a critical value. Rigorous characterization of the nonlinearities in the distortion of the polarized ion layer under an external load is necessary to systematically optimize the performance of energy-harvesting fibers. In this study, we conducted electrochemical experiments and all-atom molecular dynamics simulations to elucidate the dynamics of an ionic polarization layer on a nanotube surface. The in-plane compressive strain exerted under the mechanical tension of the energy harvester induced the radial buckling of the nanotubes, which in turn became the driving force behind the repulsion between adjacent polar ion layers. Therefore, electrochemical stability was guaranteed only under structural stability and the resulting elastic deformation experienced by each nanotube. The proposed mechanism reveals the available mechanical range wherein the polarized ionic layers can substantially function in chemomechanical energy conversion.

Effect of ionic polarization on the static permittivity of electrolyte aqueous solutions

AbstractWe developed a theoretical model with two separate components for the description of the static permittivity of aqueous electrolytes versus concentration and temperature. The first component is due to the water molecular polarization, whereas the second component is governed by the ionic polarization. We found that the permittivity part due to the ionic polarization effect is comparable to that come from the water molecule polarization for aqueous electrolytes at ambient temperatures. The microdynamic mechanism of the phenomenon, which the static permittivity of sodium chloride aqueous solution with concentration of 2.8 mol/L holds constant with the change of temperature, is clarified. The equilibrium compensation between the decrement of the permittivity part due to the water molecular polarization and the increase of that originated from the ionic polarization as increasing temperature is responsible for this phenomenon. The dipole moment reduction of water molecules as rising temperature is also confirmed by the model.

Correlation between Ionic Radii and Cation Polarizability (Review)

The polarizability approach in the glasses has been detailed studied by V. Dimitrov and T. Komatsu. Here a review is taken on the basics of their literature values classifying on number of ions and there average values of cation polarizability given by Kordes and Pauling on the basis of a couple sets of free- ion polarizabilities. Key Words: Cation, Ionic radii, Cation polarizability.

Correlation between Optical Basicity and Oxide ion Polarizability In Glass formers and Glass modifiers (Review)

The oxide ion polarizability and Optical Basicity approach in the glasses has been studied detail by V. Dimitrov and T. Komatsu, V. Dimitro and S. Sakka Duffy. Here a review is taken on the basics of their literature values. The average values of ion polarizability and average values of optical basicity given on the basics of refractive index and energy gap is correlated in glass formers, conditional glass formers, alkaline and alkaline earth oxides glass modifiers. Key Words: Ionic polarizability, Basicity, Glass formers, Conditional glass formers, alkaline and alkaline earth oxides glass modifiers.