Large Value Of Dielectric Constant Research Articles

Tuning of Dielectric Properties of Polymers by Composite Formation: The Effect of Inorganic Fillers Addition

Polymer blend or composite, which is a combination of two or more polymers and fillers such as semiconductors, metals, metal oxides, salts and ceramics, are a synthesized product facilitating improved, augmented or customized properties, and have widespread applications for the achievement of functional materials. Polymer materials with embedded inorganic fillers are significantly appealing for challenging and outstanding electric, dielectric, optical and mechanical applications involving magnetic features. In particular, a polymer matrix exhibiting large values of dielectric constant (ε′) with suitable thermal stability and low dielectric constant values of polymer blend, having lesser thermal stability, together offer significant advantages in electronic packaging and other such applications in different fields. In this review paper, we focused on the key factors affecting the dielectric properties and its strength in thin film of inorganic materials loaded poly methyl meth acrylate (PMMA) based polymer blend (single phase) or composites (multiple phase), and its consequences at low and high frequencies are explored. A wide range of different types of PMMA based polymer blends or composites, which are doped with different fillers, have been synthesized with specific tailoring of their dielectric behavior and properties. A few of them are discussed in this manuscript, with their different preparation techniques, and exploring new ideas for modified materials.

INVESTIGATION OF STRUCTURAL AND DIELECTRICAL PROPERTIES OF SOLID POLY (VINYLIDENE DIFLUORIDE-COHEXAFLUOROPROPYLENE) POLYMER FILM FOR ELECTRO CHROMIC DEVICE APPLICATIONS

An electrolyte for electro chromic device applications was prepared by simple solution cast method. The incorporation of functionalized Alkali metal (Nacl) into poly (vinilydene fluoride-co-hexafluoropropylene): Titanium dioxide (TiO2) in the ratio of 80:5 provided an enhanced dielectrical and structural properties, The casting solution, effects of the solvent and non-solvent in addition of nano scale TiO2 particles and Alkali metal (Nacl) complexes were investigated in this study. After annealing of the PVDF-co-HFP/ TiO2 and AM samples at 1600C, the FTIR study showed many spectral changes including the spectral shift to high wavenumbers and the appearance of new peaks. These spectral changes indicate increasing of crystallinity, strong molecular bonds, and some crystal phase transitions. XRD results showed the change in the crystalline phase of PVdF–co-HFP electrolyte with the addition of surface modified TiO2 and Alkali metal (Nacl). The effect of the TiO2 nanoparticles and Alkali metal (Nacl) surface functionality on the degree of crystallinity of the polymer matrix was analyzed using TGA, scanning electron microscopy (SEM) results the surface morphology and porous nature of the fabricated membrane. The particular polymer electrolyte specimen having 15 wt% Alkali metal (Nacl) exhibited the large values of dielectric constant ' in the low frequency region may be due to an enhanced level of storage of charge carriers at the electrolyte-electrode interface thereby resulting in an increase in the equivalent capacitance. Results show that tends to confirm that the best conducting sample with 15 wt% Alkali metal (Nacl) would possess the maximum number of charge carriers among the five different compositions of NCPE system considered during the present endeavor

Room temperature magnetoelectric properties of [Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3]/Ni0.8Zn0.2Fe2O4 bilayer thin films deposited by laser ablation

Ferroelectric-ferromagnetic [Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3](160 nm)/Ni0.8Zn0.2Fe2O4 (30 nm, 60 nm) bilayer thin films (abbreviated as (BZT-0.5BCT)/NZFO) have been grown on Pt/Si(100) substrate by pulse laser deposition techniques. X-ray diffraction analysis confirms polycrystalline nature of the films without any intermediate phase at the interface. The large value of dielectric constant (ε΄ ~ 2.03 × 103 at frequency 100 Hz) and remnant magnetization (Mr ~ 45.25 emu/cc) were observed at room temperature for (BZT-0.5BCT)/NZFO (60 nm) bilayer thin film. Bilayer (BZT-0.5BCT)/NZFO (30 nm) thin film exhibits saturated ferroelectric loop with large value of polarizations Pr ~ 5.57 μC/cm2 and Ps ~ 20 μC/cm2. The large value of ME coefficient (αE ~ 320 mV/cm.Oe) was obtained for (BZT-0.5BCT)/NZFO (30 nm) thin film at room temperature. This indicates its potential for lead-free ME device applications.

Engineering room-temperature multiferroicity in Bi and Fe codoped BaTiO3

Fe doping into BaTiO3 stabilizes the paraelectric hexagonal phase in place of the ferroelectric tetragonal one. We show that simultaneous doping of Bi along with Fe into BaTiO3 effectively enhances the magnetoelectric (ME) multiferroic response (both ferromagnetism and ferroelectricity) at room temperature, through careful tuning of Fe valency along with the controlled recovery of the ferroelectric-tetragonal phase. We also report a systematic increase in large dielectric constant values as well as reduction in loss tangent values with relatively moderate temperature variation of the dielectric constant around room temperature with increasing Bi doping content in Ba1−xBixTi0.90Fe0.10O3 (0 ≤ x ≤ 0.10), which makes the higher Bi–Fe codoped sample (x = 0.08) promising for use as a room-temperature high-κ dielectric material. Interestingly, the x = 0.08 (Bi–Fe codoped) sample is not only found to be ferroelectrically (∼20 times) and ferromagnetically (∼6 times) stronger than x = 0 (only Fe-doped) at room temperature, but also observed to be better insulating (larger bandgap) with indirect signatures of larger ME coupling as indicated from anomalous reduction of the magnetic coercive field with decreasing temperature. Thus, room-temperature ME multiferroicity has been engineered in Bi and Fe codoped BTO (BaTiO3) compounds.

Investigation of room temperature multiferroic properties in sol-gel derived gadolinium, cobalt doped BiFeO3 nanoceramics

Detailed studies of structural, dielectric, magnetic, ferroelectric, and optical properties of a chemically sol-gel synthesized series of Bi1 − xGdxFe1 − yCoyO3 (x = 0, 0.1 and y= 0, 0.1) nanoceramics are presented. These nanoceramics attract attention as promising candidates for application as room temperature multiferroics in spintronics devices, exhibiting an optimistic set of properties. The average particle sizes of all the samples are calculated, and it was found to be ∼45 nm from the Scanning Electron Microscopy image. The dielectric behavior of the prepared nanoceramics was investigated over a wide frequency (100 Hz–103 kHz) and a temperature (35–350 °C) range. Interestingly, a low temperature dielectric anomaly is observed at around 170 °C for Bi0.9Gd0.1Fe0.9Co0.1O3 due to the magnetoelectric coupling. A noticeably large value of dielectric constant (∼990) and a low tan δ loss have also been observed for this nanoceramic at room temperature. The complex impedance spectroscopic analysis was also performed by plotting Nyquist plots, and the corresponding activation energies are evaluated from the Arrhenius fittings. Magnetization measurements of the samples reveal the presence of weak ferromagnetism due to surface spins as well as a noticeable improvement in the magnetic properties with Gd and Co doping. Ferroelectric properties have also been observed to be slightly improved because of doping, though it becomes somewhat lossy for Gd and Co doped samples. All the promising improved properties directly depend on the subsequent increase in the bandgap from 2.29 eV to 2.45 eV, with doping in the parent BiFeO3 compound confirmed from UV–Vis spectroscopy.

Influence of Cr and Zn substitution on structural, magnetic and dielectric properties of Sr2-xZnxNi2Fe28-yCryO46 X-type hexagonal ferrite

Polycrystalline materials of Sr2-xZnxNi2Fe28-yCryO46 (x = 0.00, 0.01, 0.02, 0.03 and 0.04; y = 0.0, 0.2, 0.4, 0.6 and 0.8) X-type nano-ferrites are fabricated by sol-gel synthetic route. The TGA results of the prepared samples showed that these materials have high thermal stability. The analysis of x-ray diffraction patterns is confirmed X-type phase of these materials. The crystallite size was under 50 nm for all samples, which confirmed that these materials lie in nano-scale range. The large value of dielectric constant (91, 123) and moderate loss (0.52, 0.92) of Sr1.98Zn0.02Ni2Fe27.60Cr0.4O46 and Sr1.97Zn0.03Ni2Fe27.40Cr0.6O46 samples respectively were observed. Slope versus concentration graph indicated that the ac conductivity of all the exhibited frequency dependent behavior. Cole-Cole plots exhibited complete semicircle for these materials, which showed the grain boundary resistance inside the samples. The magnetic properties such that saturation, remanent magnetization (Ms, Mr), squareness ratio (Mr/Ms), coercivity (Hc), anisotropy constant (K) and magnetic moment are examined from hysteresis loops. The saturation magnetization was increased (45.42–52.45 emu/g) while the coercivity was decreased (414–630 Oe) by substitution of Cr3+-Zn2+. The increase in magnetic moment from 21.08 μB to 24.34 μB was observed by inclusion of Cr3+-Zn2+. The multi domain nature was evidenced by the smaller squareness ratio (0.36–0.40) of these ferrites. The high saturation magnetization and small coercivity of Sr1.98Zn0.02Ni2Fe27.60Cr0.4O46, Sr1.97Zn0.03Ni2Fe27.40Cr0.6O46 samples was obtained up to 52.45 emu/g, 49.42 emu/g and 345 Oe, 448 Oe respectively, which show their applications for absorption of electromagnetic radiation at microwave region and development of multilayer chip inductors. The dielectric properties of Sr1.98Zn0.02Ni2Fe27.60Cr0.4O46 and Sr1.97Zn0.03Ni2Fe27.40Cr0.6O46 ferrites showed that these materials might be consider for the development of super-capacitor devices.

Effect of Al3+substitution on the electrical and magnetic properties of Li-base ferrites

Aluminum substituted lithium ferrites with chemical formula Li0.6 (Ni Co)0.2Alx Fe2.2−x O4 (x = 0.0 ,0.15,0.3,0.45,0.6) have been synthesized by sol-gel method and sintered at 900 °C for 5 h. The samples were characterized by XRD, electrical, dielectric and VSM measurements. X-ray diffraction studies confirmed that all the samples exhibit single phase cubic spinel structure with space group Fd3m. The crystallite size, bond lengths, x-ray density and lattice parameters decrease with the increase of Al3+ concentration. Dielectric properties such as dielectric constant (ε′), complex dielectric constant (ε″), tangent loss (tanδ) and ac conductivity (σac) of all the samples were measured and evaluated as a function of frequency at room temperature. The variation of dielectric properties; ε′, ε″, tan and σac versus frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+. The Al-doped nano-crystalline lithium ferrite samples exhibit a very large value of dielectric constant of the order of 104. The room temperature resistivity and activation energy increases with the increase of Al3+ concentration. The temperature dependent resistivity of all samples decreases with increase of temperature indicating the semiconducting behavior. The room temperature DC resistivity increases from 1.65 × 1010 to 2.23 × 1011 ohm-cm. The small value of magnetization may be due to canting superparamagnetic spins at the surface of the samples. The decrease in the magnitude of magnetization value may also be due to the presence of Al3+ paramagnetic ions with spin-down orientation instead of Fe3+ cations with spin-up orientation in the octahedral sites. The squareness ratio (Mr/Ms) is less than 1 which indicates single domain behavior. The increase in coercivity is attributed to lattice defects and decrease is associated with the superparamagnetic behavior.

Structural, microwave permittivity, and complex impedance studies of cation (Cr, Bi, Al, In) substituted SrNi-X hexagonal nano-sized ferrites

Sr2Ni2TxFe28-xO46 (T = Cr3+, Bi3+, Al3+, In3+; x = 0.25) hexa-ferrites were fabricated via the sol-gel route. The phase temperature, which was obtained using thermo-gravimetric analysis (TGA), reveals that the X-type hexagonal phase of these materials is highly stable above 1200 °C. The phase formation was confirmed using X-ray diffraction (XRD) patterns. The variation in lattice strain shows the significant effect of substituted cations on the structure of the materials. The crystallite size of these materials was found in the range of 18–19 nm. The increase in dielectric constant, as well as with moderate loss, was observed in all substituted samples between 0.001 GHz and 1 GHz. The large values of dielectric constant were observed for Al3+ and In3+ substituted materials at higher frequency. The values of slope (n) reveal that all the materials exhibit frequency dependent ac conductivity. The Cole-Cole plots show the single semicircle for all samples. These semicircles of the Cole-Cole plots indicate that resistance inside the material is due to grains and grain boundaries. The both grain and grain boundaries resistance inside the material may cause large values of dielectric constant as well as the losses in the material. The large values of dielectric constant and impedance with moderate dielectric losses of these materials reflect their significant role in the fabrication of electronic devices as a radiation/microwave absorber or high frequency equipment components. Magnetic analysis shows the large values of magnetization and coercivity for Al3+ and In3+ substituted samples, which reflect that these materials might be beneficial for the absorption of electromagnetic radiation, formation of multilayer chip inductors and recording/storage purpose.

Effect of Cr3+ on growth, thermal, photoluminescence and electrical properties of potassium dihydrogen citrate single crystal

Potassium Dihydrogen Citrate (KDC) is well recognized food additive and hence it is interesting to investigate the influence of toxic metal doping on its properties. The pure and 0.2 mol% Cr3+ doped KDC crystals are grown using solvent evaporation technique at room temperature. The grown crystals exhibits needle shape morphology. The EDAX analysis confirms the presence of chromium along with the constituent elements of KDC crystal. The powder XRD indicates the triclinic symmetry of the grown crystals. The FT-IR spectroscopic study indicates the presence of various functional groups in the pure and doped crystals. The Cr3+ improves the thermal stability of KDC crystal. The influence of Cr3+ doping is clearly shown by large value of dielectric constant of doped KDC crystals compared to pure KDC. The variation of dielectric constant, dielectric loss and A.C. conductivity with frequency are studied. The Photoluminescence study confirms the defect in hydrogen bonding network of KDC crystal due to doping of Cr3+.

Ferroelectric and optical behavior of Pb0.5Ba1.5BiNbO6 double perovskite

Solid solution of (Pb0.5Ba1.5BiNbO6 (PBBN) poly-crystalline sample has been traversed here to study its electrical and optical behavior. For preparation of the compound conventional mixed oxide route method was adopted. To study its structure and stability we have taken care of different experimental support like room temperature X-ray diffraction (XRD), scanning electron micrograph (SEM) image, energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy. From XRD and SEM data it is confirmed that material is single phase and highly dense. The purity of the sample/absence of foreign particle was confirmed from EDS analysis. Both stretching and bending type of vibration are dominated in FTIR data of the studied compound. For electrical and optical properties of the material authors have selected the experimental set up like impedance analyzer, UV–vis and photo luminescence spectrometer. The dielectric measurement data shows compound has large value of dielectric constant (at RT) and relaxor type ferroelectric phase transition. From UV–vis and PL data it is seen material has very good optical properties having optical band gap of ∼2.08 eV which is usually useful for photo catalytic blue LED etc.

Исследование электропроводности спиртовых растворов солей

Electrical conductivity of solutions depends on the nature of the solute and solvent. It is associated with the mobility of ions that are formed during the dissociation of substances in the corresponding solvents. In solvents with large dielectric constant values, substances dissociate into their constituent ions to a greater degree. The dielectric constant of water at room temperature is 78.25. It is a universal solvent and most salts dissolve in it with the decomposition into ions. In proton solvents containing mobile hydrogen ions, salts also dissolve with dissociation into ions. Such solvents include alcohols, the dielectric constant of which is significantly less than the dielectric constant of water. To describe the electrical conductivity of salt solutions in solvents with small dielectric constant, it is proposed to use the Pisarzhevsky-Valden equation in literature. This equation assumes that solvents have a similar chemical nature and the mechanism of salt ion solvation by molecules of different solvents is the same. The degree of solvation changes significantly from one solvent to another for salts containing small ions. This is due to the different solvation of ions in different solvents. Therefore, for such solutions, Pisarzhevsky-Valden equation should not be satisfied. To account for the mechanism of ion solvation in different solvents, A.M. Shkodin proposed an equation that takes into account the dielectric constant of solvent. In this regard the possibility of describing the equivalent conductivity of alcohol solutions of salts with infinite dilution by the equations of Pisarzewski-Valden and Shkodin has been studied in this article. Electrical conductivity of the studied solutions was judged by the specific χ and equivalent to λ electrical conductivities. These two conductivities are related by the equation λ = χ/С, where С is the solution concentration. In this article, for salt solutions of with different concentrations in a certain alcohol, the values of χ and λ were found. By analyzing the dependences 1/λ = f(λС), the values of the limiting equivalent conductivity (λ∞) were found at C = 0. For solutions of each salt in different alcohols, the possibility of describing the obtained values of λ∞ by the Pisarzhevsky-Valden (λ∞· = const) and Shkodin (λ∞· = А·exp(-B/D), where  and D are viscosity and the dielectric constant of alcohol; A, B = const). It was found that the experimental data obtained for solutions of sodium iodite and chlorides of cobalt, iron (3), lithium, calcium, nickel, copper, zinc in alcohols (ethanol, propanol-2 and batanol-1) are better described by the Shkodin equation.

Electrical properties of Strontium Barium Niobate [formula omitted] thin films deposited by pulsed laser deposition technique

Growth of Sr0.6Ba0.4Nb2O6 (SBN60) thin films on Pt-Si substrate has been carried out using Pulsed Laser Deposition (PLD) technique by varying the oxygen pressure from 1.33×10−3mbar to 26.67×10−3mbar and at a fixed substrate temperature of 800°C. The crystalline behavior of as-deposited films was studied using X-ray diffraction technique indicating the preferential growth along c-axis. The Metal- Ferroelectric- Metal (MFM) structure was used to measure the current-voltage (I-V) and dielectric properties of as-prepared SBN thin film. A large value of dielectric constant of about 503 at 1 MHz was obtained for SBN60 thin film with good ferroelectric polarization-hysteresis loop (Pr=5.32μC/cm2 and Pmax=9.86μC/cm2 . A high value of total stored energy density 4.60J/cm2 with an efficiency of 17% efficiently contributes towards its potential application in non-volatile memory devices.

Preparation, structural, spectroscopic and magneto-electric properties of multiferroic cadmium doped neodymium manganite

Cadmium doped neodymium manganite having general formula Nd1−xCdxMnO3 where x = 0.05, 0.20 were prepared by solid state reaction technique. The effect of cadmium doping on the structural, dielectric and magnetic properties were understood by various characterization probes like X-ray diffractometer, scanning electron microscope, energy dispersive X-ray analyzer, Fourier transform infrared spectroscope, impedance analyzer, vibrating sample magnetometer and resistivity measurements for low temperature using four probe method. XRD analysis confirms the single phase formation with perovskite structure having orthorhombic phase. The crystallite size was found to be in the range of 30–50 nm as determined by Debye-Scherer relation and Williamson’s Hall method. Density of the samples were determined theoretically and experimentally and compared with the results obtained by Archimedes principle. The scanning electron micrograph shows that the particle size distribution is almost homogeneous and spherical in shape for all grains. FTIR spectra depict the presence of various atomic bonds within a molecule and the present study depicts the presence of the Mn–O bond and O–Mn–O stretching for these compositions. A very large value of dielectric constant was observed at low frequencies due to the presence of grains and interfaces. The variation of dielectric constant value with the change in frequency and temperature were studied and compared for two compositions. Magnetization study confirms the phase transition of the materials from the paramagnetic to ferromagnetic behaviour of the material at low temperature. The variation in resistance below room temperature were studied and compared for both the compositions.

Dielectrical performance of high-k yttrium copper titanate thin films for electronic applications

The increasing constraints in the miniaturization of modern electronic devices is driving the search for new high-k dielectric materials. Rare-earth transition metal oxides are very interesting because of the large values of dielectric constant observed in bulk samples. Here, we report on a comparison among the dielectric properties of yttrium copper titanate (YCTO) thin films and those of commonly used dielectrics such as SiO2 and MgO, grown in similar device structures. The YCTO permittivity was found to depend strongly on the oxygen pressure during deposition and can reach values even higher than those reported in bulk YCTO with good performances in terms of losses.

Stress induced enhanced polarization in multilayer BiFeO3/BaTiO3 structure with improved energy storage properties

Present work reports the fabrication of a multilayer (5-layer) structure of BiFeO3(BFO)/BaTiO3(BTO) using spin-coating technique. The crystallographic structure, surface morphology and ferroelectric behavior of multilayer structure in metal-ferroelectric-metal capacitor have been studied. Le-Bail refinement of X-ray diffraction data revealed the formation of polycrystalline pure perovskite phase with induced stress. The values of remnant (Pr) and saturation polarization (Ps) for BFO/BTO multilayer structure are found to be 38.14 μC/cm2 and 71.54 μC/cm2 respectively, which are much higher than the corresponding values reported for bare BFO thin film. A large value of dielectric constant of 187 has been obtained for multilayer structure with a low leakage current density of 1.09 × 10−7 A/cm2 at applied bias of 10 V. The BFO/BTO multilayer structure favors the enhanced energy storage capacity as compared to bare BFO thin film with improved values of energy-density and charge-discharge efficiency as 121 mJ/cm3 and 59% respectively, suggesting futuristic energy storage applications.

Refractive index, band gap energy, dielectric constant and polarizability calculations of ferroelectric Ethylenediaminium Tetrachlorozincate crystal

Single crystal of Ethylenediaminium Tetrachlorozincate has been grown by slow evaporation method. The single crystal XRD study confirms the orthorhombic structure of the crystal. The presence of functional group vibrations are ascertained through FTIR and Raman studies. In optical studies, the insulating behaviour of the material is established by Tauc plot. The refractive index and the real dielectric constant of the crystal are calculated. The electronic polarizability in the high frequency optical region is also calculated from the dielectric constant values by using the Clausius–Mossotti equation. The large value of dielectric constant is identified through dielectric studies and it points to the ferroelectric behaviour of the material. Further an experimental study confirms the ferroelectric behaviour of the material. The total polarizability of the crystal owing to the space charge, dipole, ionic and electronic polarizability contributions is obtained experimentally, and it matches well with the theoretically obtained value from Penn analysis. Further, Plasmon energy and Fermi energy of the material are also calculated using Penn analysis.

Robust dielectric properties of B-site size-disordered hexagonal Ln2CuTiO6 (Ln = Y, Dy, Ho, Er, and Yb)

Hexagonal Ln2CuTiO6 (Ln = Y, Dy, Ho, Er, and Yb) exhibits a rare combination of interesting dielectric properties, in the form of relatively large dielectric constants (ϵ′>30), low losses, and extremely small temperature and frequency dependencies, over large ranges of temperature and frequency [Choudhury et al., Appl. Phys. Lett. 96, 162903 (2010) and Choudhury et al., Phys. Rev. B 82, 134203 (2010)], making these compounds promising as high-k dielectric materials. The authors present a brief review of the existing literature on this interesting class of oxides, complimenting it with spectroscopic data in conjunction with first-principles calculation results, revealing a novel mechanism underlying these robust dielectric properties. These show that the large size differences in Cu2+ and Ti4+ at the B-site, aided by an inherent random distribution of CuO5 and TiO5 polyhedral units, frustrates the ferroelectric instability, inherent to the noncentrosymmetric P63 cm space group of this system, and gives rise to the observed relatively large dielectric constant values. Additionally, the phononic contributions to the dielectric constant are dominated primarily by mid-frequency (>100 cm−1) polar modes, involving mainly Ti4+ 3d0 ions. In contrast, the soft polar phonon modes with frequencies typically less than 100 cm−1, usually responsible for dielectric properties of materials, are found to be associated with non-d0 Cu2+ ions and to contribute very little, giving rise to the remarkable temperature stability of dielectric properties of these compounds.

Dielectric properties of carbon-, silicon-, and germanium-based polymers: A first-principles study

A knowledge of factors that control the electronic structure and dielectric constant of materials would be valuable in the design of new insulators with attractive dielectric properties. In an attempt to systematically and directly understand the role of chemical composition and atomic configuration in determining such properties, we have studied (using first-principles computations) nine homopolymer systems based on $XY$${}_{2}$ building blocks, where $X=\mathrm{C}$, Si, or Ge and $Y=\mathrm{H}$, F, or Cl. Two possible generic configurations were explored, and our computations utilized dispersion-corrected semilocal exchange-correlation functionals as well as hybrid functionals. Correlations between stability, electronic structure features, infrared intensities, and the dielectric response are established across the chemical and configurational space considered. Homopolymers containing GeF${}_{2}$ or GeCl${}_{2}$ building blocks are identified as particularly promising. These systems display large dielectric constant values (regardless of the underlying crystal structure) and may display a large band gap for particular configurations. The design of a polymer insulator with optimal dielectric constant and band gap may require consideration of heteropolymers (e.g., involving CH${}_{2}$ and GeF${}_{2}$ building blocks). We provide a convenient strategy for the rapid exploration of that extended chemical and configurational space.

Enhanced magnetic and dielectric properties of Eu and Co co-doped BiFeO3 nanoparticles

Bi1−xEuxFe1−yCoyO3 (x = 0, 0.01; y = 0, 0.01) nanoparticles, having an average size of 13 nm, were prepared by a simple sol gel route. Strong electronegativity of Eu3+ and smaller oxidation-reduction potential of Co3+/Co2+ (0.55 eV) than Fe3+/Fe2+ (1.3 eV) increase the concentration of Fe3+ ions with doping. Distinct magnetic hysteresis and complete saturation of magnetisation indicate the presence of ferromagnetic phase. The successful co-doping of Eu and Co into BiFeO3 (BFO) lattice dramatically enhances the saturation magnetization (Ms) and coercivity (Hc) by about 20 times than that of pure BiFeO3. A large value of dielectric constant of about 650, low loss (<0.001), and small leakage current density (1.79 × 10−8 A/cm2) are observed for the co-doped sample.

Dielectric enhancement in cadmium sulfide—poly(methacrylic acid-ethylene glycol dimethacrylic acid) nanocomposite through interfacial interaction

Dielectrical property on poly(methacrylic acid-ethylene glycol dimethacrylate) [P(MAA-EDMA)] attached with nanosized CdS particles have been studied. The attachment of CdS nanoparticles alters the dielectric property of CdS-P(MAA-EDMA) samples. By addition of a certain amount of CdS nanoparticles, the dielectric constant at room temperature and 100 Hz of the CdS-P(MAA-EDMA) is enhanced by ca. 500 times, which is attributed to the interfacial interaction of CdS nanoparticles with polymer surface. The large value of dielectric constant is due to interfacial space charge polarization.