Decrease In Dc Conductivity Research Articles

Impedance dynamics in tandem solar cells based on c-Si with upper layers of CsPbBr3 (CsPbI3) perovskite nanocrystals

The application of an additional nanoparticle layer is a common practice for enhancing the optical and electrical properties of third-generation solar cells. In this study, we present the results of impedance spectroscopy (IS) for modified solar cells using Nyquist and Bode diagrams. The structure investigated consists of a conventional double junction based on crystalline silicon (c-Si) coated with thin films of inorganic perovskite nanocrystals (NC) of lead halides CsPbI3 and CsPbBr3. The latter are characterized by a significant phonon disorder, which leads to unique electron-phonon interactions and dielectric responses. The IS results indicate that, under the same conditions, the measured Nyquist plots align well with the simulated ones. An equivalent circuit model is proposed, featuring ohmic resistance, recombination resistance, and geometric capacitance. These elements arise due to charge accumulation, charge transfer resistance, and/or additional interfacial electronic states. The study finds that the introduction of a CsPbI3 layer enhances the photoresponse under bias conditions, but this photoresponse leads to a decrease in DC conductivity. In contrast, the addition of a CsPbBr3 layer obstructs the photoresponse under bias while slightly improving the photoresponse in the absence of an applied voltage. The results obtained contribute to the improvement of tandem solar cell characteristics featuring top layers of perovskite nanocrystals.

Enhanced electrical properties of polypropylene insulation based on β‐nucleated crystallization regulation for high‐voltage direct current cable

AbstractThis study investigates the effect of crystallisation regulation on the electrical properties of β‐modified polypropylene (PP) insulation. Various β‐modified polypropylene insulation samples are prepared by controlling the melting temperature within the range of 180°C–200°C, and the ensuing crystallization characteristics of polypropylene insulation are evaluated. It is observed that the crystallinity decreased with increase in melting temperature, while the β crystal fraction and the lamellae long period increased. Notably, PP insulation subjected to a melting temperature of 200 °C demonstrates a substantial 47.1% decrease in DC conductivity, accompanied by a notable 22.6% reduction in space charge accumulation, concomitant with a significant 14.6% enhancement in DC breakdown strength. Additionally, a higher β crystal fraction in PP insulation is found to correspond to an increased density of deep traps, notably at an energy level of 0.95 eV. The elevated melting temperature effectively eradicates the melting memory effect, thereby facilitating the induction of β crystals by the β‐nucleating agents. The parallel lamellae structure inherent in β crystals serves to diminish interface defects between spherulites, consequently mitigating carrier mobility, curtailing space charge accumulation and enhancing breakdown strength.

Investigating the charge transport mechanism and dielectric properties in nickel oxide polyaniline nanocomposites

A simple precipitation method was employed to synthesise Nickel Oxide (NiO) nanoparticles and in-situ polymerization method was employed to synthesise Polyaniline (PANI) and PANI/NiO nanocomposites. To investigate the charge transport mechanism, DC and AC conductivity studies have been carried out. The drastic decrease in DC conductivity by two orders with an addition of NiO is noticed. Impedance and AC conductivity characteristics of these composites were examined in the frequency ranging from 10 Hz to 8 MHz. All samples obey Jonscher's Power law of disordered material at higher frequencies. The values of dielectric constant as well as dielectric loss decreased with an increase in applied frequency for all the samples. The samples show non-Debey relaxation mechanism verified by Havriliak – Negami model. Composite sample 5 wt % NiO show low tangent loss behaviour which are of importance in high frequency device applications. The obtained results are promising applications for energy storage applications and organic electronic devices.

Influence of Er/Fe Substitution on Mg-Zn Nanoparticles’ Electromagnetic Properties and Applications

Mg0.8Zn0.2ErxFe2-xO4 (x = 0.00, 0.005, 0.01, 0.015, 0.02, and 0.025) nanoparticles made using the citrate gel autocombustion process were examined for their structure, morphology, and behavior. The single-phase cubic spinel structure was formed according to the diffraction pattern. Observations revealed that as the Er focus went from to 0.0 to 0.025, the average crystallite size (D) increased from 12.4 to 18.6 nm. The findings of the SEM and EDAX analyses reveal that the particles are uniform, with just a little amount of agglomeration and no impurity pickup. Nanoparticles from transmission electron microscopes (TEM) were present, the range from 12 to 19 nm. In IR spectroscopy using the Fourier transform (FTIR), nearly all the spinel ferrites presented generate two absorption bands that have wavelengths of around 400 cm and 600 cm. The BET surface area of the Er3+ ion doping Zn-Mg ferrites rises from 23.860 m2/gm to 29.845 m2/gm. The TG–DTA analysis of the prepared samples confirms the thermal stability of the samples; the temperature ranges from 100 to 750 °C.The transition temperature (Seebeck coefficient) of the samples was studied using thermoelectric power (TEP) measurement studies, and it was found that all the samples showed N-type semiconductor behavior. With an increase in erbium concentration, DC conductivity decreases. At room temperature, the magnetic characteristics of hysteresis loops, squareness ratio (SQR), anisotropy constant (K), magnetic moment (), coercivity (Hc), saturation magnetization (Ms), and retentivity (Mr) were examined. When erbium concentration rises, the magnetic moment (B) increases. The saturation magnetization values were 288.4615 and 244.5266 emu/g, and squareness ratio values from 0.01554 to 0.03303 were observed. These materials are converted from hard permanent magnet materials to soft magnet materials.

Effect of Cyclic Olefin Copolymer on Dielectric Performance of Polypropylene Films for Capacitors

In this article, aiming at the high conductance loss and low breakdown strength of the polypropylene (PP) film under a high-temperature environment, we attempt to improve the dielectric properties of PP films by blending cyclic olefin copolymer (COC). It is shown that these two materials have good interfacial compatibility. COC has little effect on the crystal form and dielectric loss of the PP/COC film because it is an amorphous polymer without the polar group. At 105 °C, a low proportion of the COC is beneficial to the decrease of dc conductivity and the increase of the breakdown strength. Since the glass transition temperature of COC is much higher than PP, the dimensional stability of the PP/COC film is improved at high temperatures. The cyclic structure of COC restricts the movement of PP molecular chains in the free volume, which plays an important role in inhibiting the migration of carriers and improving the breakdown properties. This method provides a feasible idea to improve the high-temperature resistance of metalized film capacitors (MFCs).

Characterization of Ionic Transport in Li2O-(Mn:Fe)2O3-P2O5 Glasses for Li Batteries.

We present a systematic study of the lithium-ion transport upon the mixed manganese-iron oxide phosphate glasses 3Li2O-xMn2O3-(2-x)Fe2O3-3P2O5(LMxF2-xPO; 0≤ x ≤2.0) proposed for the use in a cathode for lithium secondary batteries. The glasses have been fabricated using a solid reaction process. The electrical characteristics of the glass samples have been characterized by electrical impedance in the frequency range from 100 Hz to 30 MHz and temperature from 30 °C to 240 °C. Differential thermal analysis and X-ray diffraction were used to determine the thermal and structural properties. It has been observed that the dc conductivity decreases, but the activation energies of dc and ac and the glass-forming ability increase with the increasing Mn2O3 content in LMxF2-xPO glasses. The process of the ionic conduction and the relaxation in LMxF2-xPO glasses are determined by using power-law, Cole-Cole, and modulus methods. The Li+ ions migrate via the conduction pathway of the non-bridging oxygen formed by the depolymerization of the mixed iron-manganese-phosphate network structure. The mixed iron-manganese content in the LMxF2-xPO glasses constructs the sites with different depths of the potential well, leading to low ionic conductivity.

Structure-Property Correlation in Sodium Borophosphate Glasses Modified with Niobium Oxide

Bulk glasses of the series (100−x)[0.4Na2O-0.2Nb2O5-0.4P2O5]-xB2O3 with x = 0–48 mol% B2O3 were prepared by slow cooling in air. Their glass transition temperature increases within the range of 0–16 mol% B2O3, but further additions of B2O3 result in its decrease. Their structure was investigated by Raman, 11B, and 31P MAS NMR spectroscopy. The relative number of BO4 units decreases with increasing B2O3 content, while the number of BO3 units increases up to 59 % at x = 48. The upfield shift of a broad resonance peak in the 31P MAS NMR spectra is ascribed to an increasing connectedness of the structural network with increasing B2O3 content. Strong Raman band at 916–929 cm−1 shows on the presence of NbO6 octahedra in the structural network of these glasses. With the B2O3 addition, a decrease in DC conductivity is observed, which is attributed to the decrease in the concentration of Na+ ions.

Ion dynamics in a highly compressed solution of tetra-ethylammonium – tetra-fluoroborate salt in propylene carbonate: A study in the equilibrium and glassy states

Electrical conductivity of a solution of (Et4N+,BF4−) in propylene carbonate is measured by varying the pressure and temperature along different thermodynamic paths: pressure is increased from a low value in the liquid state up to ̴ 3.6 GPa well above the glass-transition pressure PG, along isotherms at temperatures between ̴ 295 K and ̴ 326 K. Up to a crossover pressure Pcross ̴ 1 GPa, the dc-conductivity decreases and obeys the Walden rule. Above Pcross, an anomalous pressure-dependence of the conductivity spectra is observed, leading to an increase in dc-conductivity up to PG. The dc-conductivity obeys density scaling, showing in the glassy state an exponential decrease against the scaling variable, independently of the thermobaric history of the sample. The conductivity spectra obey the time-temperature-pressure-superposition principle, therefore, the ion dynamics is not affected by the transition from the liquid state to the non-ergodic glassy state.

DIELECTRIC BEHAVIOUR OF MAGNETIC NICKEL NANOPARTICLES ENCAPSULATED IN SILICA

The impedance measurement showed activation energy of 1.3 eV and decrease in dc conductivity with temperature. The high dielectric constant over a wide frequency range is explained as a consequence of concentration of Ni much higher than the percolation threshold. The conductivity mechanism is dominated by tunneling at low frequency and electron hopping at high frequencies. The material suffers a low loss in high frequency range, making it suitable for high frequency magnetic applications.

Graftable voltage stabilizer for enhancing insulation performance of crosslinked polyethylene

AbstractWith the popular application of alternating current/direct current (AC/DC) hybrid power grid, ultra‐high‐voltage (UHV) AC/DC cables of long‐distance and large‐capacity transmission systems have been strongly demanded. Voltage stabilizers are widely used to resist AC electrical tree of cross‐linked polyethylene (XLPE) insulation materials, but poor compatibility with polymer matrix limited improvement of DC insulation performance. In this research, the maleic anhydride‐modified 2,4‐dihydroxybenzophenone as a novel voltage stabilizer 4‐(4‐benzoyl‐3‐hydroxyphenoxy)‐4‐oxobut‐2‐enoic acid (MDVS) was synthesized to improve the electrical properties of XLPE. The XLPE‐g‐MDVS with different contents of MDVS was prepared, and both AC electrical properties and DC electrical properties were tested. The results indicate that the modified XLPE retain the characteristic of voltage stabilizer to resist AC electrical tree and improve breakdown strength, and to exhibit excellent DC insulation performance in a wide temperature range. In the comparison with the pristine XLPE, the graft of MDVS can significantly suppress space charge accumulation and decrease DC conductivity. At 70°C, the maximum amount of space charge density of XLPE‐g‐1.2wt%MDVS is 56.2% lower than that of XLPE, and the DC conductivity decreases by nearly two orders of magnitude. Furthermore, the DC breakdown strength of XLPE‐g‐1.2wt%MDVS materials exhibit higher than that of the pristine XLPE. In addition to the self‐excited energy dissipation of the voltage stabilizer, quantum chemical calculations demonstrated that the improvement of DC performance attributed to the deep traps introduced by MDVS.

Mitigation of Surface Oxidation in Sb2Se3 Thin Films Via Te Doping: An Effective Strategy Towards Realization of Efficient Electronic Devices

Sb2Se3 and Te-doped Sb2Se3 films of ∼250 nm film thickness were deposited using a facile thermal evaporation technique from the bulk powder synthesized via the melt quenching technique. Thermogravimetric analysis of pure and Te-doped Sb2Se3 alloys in bulk form indicates decomposition of the alloys in the 303–673 K temperature range. The X-ray diffraction pattern revealed single-crystalline orthorhombic phase stabilization of as-prepared alloys in bulk as well as in the annealed thin films. Phase formation is also evident in the recorded Raman spectra from the appearance of two peaks at ∼189 and 210 cm–1, which are ascribed to the Sb2Se3 Ag mode. The absorbance spectra of as-annealed pure Sb2Se3 and Te-incorporated Sb2Se3 films exhibit significant reduction with Te doping due to an increase in the optical band gap. The conductivity in as-annealed Sb2Se3 and (0.08%)Te-doped Sb2Se3 films recorded from 308 K (room temperature) to 392 K show a decrease in DC conductivity and activation energy with the insertion of Te in the Sb2Se3 system. Such a trend in conductivity and activation energy is attributed to arise as a result of structural changes as well as defect passivation enabled by Te insertion in the alloy. Interestingly, the DC conductivity is in the range of ∼10–7 Ω–1 cm–1 at 308.5 K, which is 10 times higher than that of the previously reported conductivity of Sb2Se3 films. Presently, the nonpreferential grain growth, undesirable deep-level defects, and surface oxidation in Sb2Se3 thin films are pressing issues that render them unsuitable for practical application in devices. Herein, this study brings to the fore a strategy to overcome these issues by doping Te in Sb2Se3 thin films, and hence it is a step forward towards the replacement of environmentally toxic CdTe-based devices.

High-temperature Breakdown Performance Improvement of Polypropylene Films Based on Micromorphology Control

In this paper, a modification method of polypropylene (PP) films is proposed for capacitors by micro doping of carboxylated cellulose nanocrystals (C-CNCs). Results prove that crystallization process of films is promoted, due to the entanglement effect of acicular ultra-structures of C-CNCs on PP molecular chains. With a proper doping content (0.01 wt%), the thermal properties are elevated, and the DC conductivity decreases by raising crystallinity and limiting carrier movement. Modified films possess a restricted dielectric loss at low frequencies because of regular microstructures and decreased conduction loss. Based on DC experiments at different temperatures, the breakdown strength of C-CNC/PP films shows an increase by approximately 51% at 85 °C, basically equaled to the level of pure PP at 25 °C. The mechanism is attributed to deep trap sites, which are introduced by the large crystal region and result in short free path in carrier transport. This novel PP film shows a great potential for application under thermal-electrical compound field in power systems.

Gel point determination of gellan biopolymer gel from DC electrical conductivity

Abstract Gellan is an anionic bacterial polysaccharide, which in aqueous solution dissociates into a charged gellan polymer molecule containing carboxyl ions and counter ions and forms thermoreversible gel under appropriate conditions. In this study, we investigated the effect of polymer concentration, the concentration of added monovalent metallic ion, and temperature on the DC electrical conductivity of the gellan. Results suggest that the DC conductivity decreases with the increasing polymer concentrations and the added monovalent metallic ions. Such a decrease in DC conductivity can be attributed to the reduction of the mobility of counter ions due to the increase in the crosslinking density of the gellan network. DC conductivity of gellan gels was increased with temperature, which is interpreted as the dissolution of physically cross-linked networks, thus increasing the mobility of counter ions. The behavior of temperature variation of DC electrical conductivity reveals an abrupt change at a specific temperature, which can be considered a way to determine the gel point or sol–gel transition temperature T c of this thermoreversible biopolymer gel. This result agrees with that of rheological measurements where the viscosity showed a similar trend with temperature and diverges to infinity at the temperature close to T c.

Compatibilization of Vulcanized SBR/NBR Blends using Cis-Polybutadiene Rubber: Influence of Blend Ratio on Elastomer Properties

Blends composed of styrene butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were fabricated by melt blending technique using two-roll mill blend machine. Cis- polybutadiene rubber (CBR) was used as a compatibilizer for enhancing the homogeneity between SBR and NBR phases in blends. Although, no previous reports were found to discuss improving electrical properties of vulcanized SBR/NBR blends using unfilled rubber system (i.e. no fillers incorporated). Raman spectra and SEM images indicate that a significant compatibility within the rubber matrix is observed, due to using CBR compatibilizer. The effect of SBR/NBR blend ratio on curing characteristics, physico-mechanical properties, and physicochemical properties (e.g. network characteristics and thermodynamic parameters) were studied. SBR/NBR blend showed comparatively better mechanical properties, compared to each other individually rubber system. Curing parameters e.g. Mooney viscosity and hardness were increased, while a reduction in cure time and specific gravity was observed with increasing SBR ratio in blends. Results revealed that increasing SBR resulted in an enhancement of the tensile strength, modulus at 300 % and elongation at break up to 40 phr, and then gradually decreased. The TGA results indicated that SBR/NBR blends were thermally decomposed at a temperature range of 340-520°C. The notable decrease of DC conductivity (?dc) of vulcanized blends is owing to the decrease of NBR, which is a polar portion and is responsible for increasing the conductivity of vulcanized blends. This proved that the targeted industrial applications for vulcanized blends are entirely depending upon SBR/NBR blend in elastomers matrix.

Compatibilization of Vulcanized SBR/NBR Blends using Cis-Polybutadiene Rubber: Influence of Blend Ratio on Elastomer Properties

Blends composed of styrene butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were fabricated by melt blending technique using two-roll mill blend machine. Cis- polybutadiene rubber (CBR) was used as a compatibilizer for enhancing the homogeneity between SBR and NBR phases in blends. Although, no previous reports were found to discuss improving electrical properties of vulcanized SBR/NBR blends using unfilled rubber system (i.e. no fillers incorporated). Raman spectra and SEM images indicate that a significant compatibility within the rubber matrix is observed, due to using CBR compatibilizer. The effect of SBR/NBR blend ratio on curing characteristics, physico-mechanical properties, and physicochemical properties (e.g. network characteristics and thermodynamic parameters) were studied. SBR/NBR blend showed comparatively better mechanical properties, compared to each other individually rubber system. Curing parameters e.g. Mooney viscosity and hardness were increased, while a reduction in cure time and specific gravity was observed with increasing SBR ratio in blends. Results revealed that increasing SBR resulted in an enhancement of the tensile strength, modulus at 300 % and elongation at break up to 40 phr, and then gradually decreased. The TGA results indicated that SBR/NBR blends were thermally decomposed at a temperature range of 340-520°C. The notable decrease of DC conductivity (σdc) of vulcanized blends is owing to the decrease of NBR, which is a polar portion and is responsible for increasing the conductivity of vulcanized blends. This proved that the targeted industrial applications for vulcanized blends are entirely depending upon SBR/NBR blend in elastomers matrix.

Non suitability of silver ion conducting polymer electrolytes based on chitosan mediated by barium titanate (BaTiO3) for electrochemical device applications

In this study, we report the non-suitability of silver ion conducting polymer electrolytes mediated by barium titanate (BaTiO3) for electrochemical device applications. Various amounts of BaTiO3 fillers have been added to chitosan: silver triflate (CS:AgTf) solution to prepare polymer composites. Electrical impedance spectroscopy (EIS) has been used to characterize electrical properties of the samples. Charge transfer resistance has been correctly estimated for the samples using electrical equivalent circuit (EEC) model. At 3 and 5 wt % of BaTiO3 filler, the charge transfer resistance was found to increase and diameter of the impedance plots are shown to be widened due to the increase of grain boundaries. The dielectric constant is also observed to decrease with the increase of BaTiO3 concentration. DC conductivities for the composite samples are estimated from AC conductivity spectra. The DC conductivity was found to decrease from 4.7 × 10−7 S/cm to 5.4 × 10−9 S/cm for CS:AgTf system incorporated with BaTiO3 filler. Such decrease has revealed that the electrolytes are not suitable for electrochemical device applications. Shifting of relaxation peaks of imaginary part of electric modulus towards low frequency side has indicated the increase of relaxation time and hence the decrease in DC conductivity. The relaxation processes are also studied using Argand plots. The existence of metallic silver nanoparticles has been examined via ultraviolet–visible (UV–Vis) spectroscopy. The UV–Vis spectra showed that surface plasmon resonance (SPR) peaks are broadened and increased in their intensity as the BaTiO3 concentration increased from 1 to 3 wt %. This implied that the reduction rate of silver ions to silver nanoparticles is increased. Moreover, disappearance of SPR peak was found for the BaTiO3 concentration of 5 wt %, revealing the bulk formation of silver metals. Transmission electron microscopy (TEM) images were obtained for the samples, in which the formation of bulk metallic sizes of silvers was found to be obvious. This growth of bulk silver metals at high BaTiO3 concentration was further supported by optical and scanning electron microscopy (SEM) techniques. The distribution of white specs due to silver nanoparticles on the surface of chitosan-silver triflate solid film was investigated. Large white sheets were appeared on the surface of CS:AgTf incorporated with 5 wt% BaTiO3 and related to the huge amount of aggregated metallic silver particles. Sharp intense peaks due to metallic silver particles and weak peaks due to BaTiO3 fillers have been observed in the analyses of energy dispersive X-ray (EDX) spectra.

Effect of mechanical mixing method of preparation of polyaniline-transition metal oxide composites on DC conductivity and humidity sensing response

In the present work, optimized polyaniline-titanium dioxide (PANI-TiO2) and polyaniline-yttrium oxide (PANI-Y2O3) composites were prepared by mechanical mixing of chemically synthesized PANI with TiO2 and Y2O3 transition metal oxides respectively. The Fourier transform infrared spectroscopy (FTIR) analysis confirmed relative decrease in depth of delocalization band of PANI in the composites as compared to that in PANI. The X-ray diffraction (XRD) studies confirmed decrease in degree of crystallinity and increase in inter-chain separation of PANI in the composites as compared to those of PANI. The scanning electron microscopy (SEM) images confirmed relatively more agglomerated and porous granular morphology of the composites as compared to that of PANI. Decrease in DC conductivity of the composites as compared to that of PANI confirmed experimentally and then supported theoretically by one dimensional variable ranging hopping (VRH) model. The PANI-TiO2 and PANI-Y2O3 composites, when studied for their humidity sensing performance, recorded remarkable maximum sensing response of 94 and 96% respectively at 97% RH as compared to 40% of PANI. The response and the recovery time of PANI-TiO2 composite were 95 and 122 s respectively and those of PANI-Y2O3 composite were 50 and 80 s respectively. Humidity sensing stability of the composites tested for a period of 1 month and confirmed.

Effects of V2O5 on elastic, structural, and optical properties of mixed ionic–electronic 20Na2O–20CaO–(60 − x)B2O3–xV2O5 glasses

Glass samples [20Na2O–20CaO–(60 − x)B2O3–xV2O5, where 0 ≤ x ≤ 2.5 mol%] were prepared using melt-quenching method to study the mixed ionic–electronic (MIE) effect on the elastic and optical properties of the glasses. Ultrasonic velocities, elastic moduli, hardness, and Debye temperature decreased to a minimum at x = 1.5 mol%. The initial decrease in the elastic moduli may have been caused by the increase in the number of non-bridging oxygen (NBO). In this process, V2O5 acted as a modifier at low vanadium concentration but changed to a network former at x > 1.5 mol%. The FTIR spectra showed the presence of VO4, VO5, BO3, and BO4 vibration groups, and this result confirmed that V2O5 played a dual role in the glass network. Considerable decrease in dc conductivity (x = 1.5 mol%) signified a blocking effect on the ionic current in the MIE glasses. Interestingly, the observed anomaly in the elastic moduli coincided with the dc conductivity minima, indicating possible influence of the MIE effect on the elastic anomaly. Quantitative analysis using ideal bulk compression and ring deformation models showed a decrease in Kbc/Ke at x > 1.5 mol% which implies that ring deformation was reduced in the region. Furthermore, the MIE effect also influenced the optical properties of the investigated glasses. The optical band gap (E opt) and refractive index exhibited minimum and maximum values, respectively, at x = 1.5 mol%. The increase in concentration of NBOs and the defect states elucidated the significant changes in the E opt of the glasses.

Effect of iron doping at Mn-site on complex impedance spectroscopy properties of Nd0.67Ba0.33MnO3 perovskite

ABSTRACTThe effect of Fe-doping at Mn-site on the structural and electrical properties of Nd0.67Ba0.33Mn1−xFexO3 (0 ≤ x ≤ 0.05) perovskites has been investigated. X-ray diffraction patterns show that the structural parameters change slightly due to the fact that the Fe3+ ions replacing the Mn3+ have similar ionic radius. The electrical properties of these samples have been investigated using complex impedance spectroscopy technique. a function of the frequency at different temperatures. When increasing the Fe-content, a decrease of dc conductivity was observed throughout the whole explored temperature range and the deduced activation energy values are found to increase from 128 meV for x = 0 to 166 meV for x = 0.05. The curves of the imaginary part of impedance (Z″) show the presence of relaxation phenomenon in our samples. The complex impedance spectra show semicircle arcs at different temperatures and an equivalent circuit of the type of Rg + (Rgb//Cgb) has been proposed to explain the impedance results.

Highly Insulating Polyethylene Blends for High-Voltage Direct-Current Power Cables

The insulation of state-of-the-art extruded high-voltage direct-current (HVDC) power cables is composed of cross-linked low-density polyethylene. Driven by the search for sustainable energy solutions, concepts that improve the ability to withstand high electrical fields and, ultimately, the power transmission efficiency are in high demand. The performance of a HVDC insulation material is limited by its residual electrical conductivity. Here, we demonstrate that the addition of small amounts of high-density polyethylene (HDPE) to a low-density polyethylene (LDPE) resin results in a drastic reduction in DC conductivity. An HDPE content as low as 1 wt % is found to introduce a small population of thicker crystalline lamellae, which are finely distributed throughout the material. The change in nanostructure correlates with a decrease in DC conductivity by approximately 1 order of magnitude to about 10-15 S m-1 at high electric fields of 30 and 40 kV mm-1 and elevated temperature of 70 °C. This work opens up an alternative design concept for the insulation of HVDC power cables.