Dielectric Impedance Analysis Research Articles

Dielectric and Thermal Behavior of Polystyrene/Sr2TiMnO6 (STMO) Composites

Materials with high dielectric permittivity are in demand due to their potential applications in microelectronics, capacitors and related fields. Polymer/ceramic composites, due to their improved properties, can be studied to meet this demand. In this work, high permittivity double perovskite Sr2TiMnO6 (STMO) ceramics were synthesized by solid state reaction route and polystyrene (PS) composite thick films (∼200 μm) with up to 50 vol% loading of STMO were prepared by solution casting technique. The composite films were characterized using X-ray diffraction and Fourier transform infra-red spectroscopy for their structural properties. Microstructure of the composites was examined using scanning electron microscopy. Thermal behavior was studied using differential scanning calorimetry and thermo-gravimetric analysis. Dielectric properties, such as permittivity, loss and AC conductivity were measured using a dielectric impedance analyzer. Permittivity and dielectric loss of the base polymer were found to increase with the addition of STMO. Glass transition for composites shifted to higher temperature than that of pure PS. The composites exhibited enhanced thermal stability and these composite films can be explored as dielectric materials for capacitor applications.

Dielectric properties of natural Borneo woods: Keranji, Kayu Malam, and Kumpang

The dielectric behavior and properties of three types of Sarawak woods, under various conditions (untreated, alkaline treated, potassium carbonate treated, and heat treated), were investigated and discussed. The dielectric constant, loss, and dissipation factor tests were conducted via a dielectric impedance analyzer. The results revealed that the dielectric properties decreased in relation to an increase in frequency. With considerations to the treatment method, the highest dielectric constant values for the untreated samples were found in Kumpang wood, the highest dielectric constant values for the heat-treated samples and potassium carbonate treated samples were found in Keranji wood, and the highest dielectric constant values for sodium hydroxide treated samples were found in Kayu Malam wood. Therefore, it was evident that the physical properties, e.g., internal structure, density, moisture, temperature, etc., could affect the dielectric behavior and properties of the wood materials.

Effect of lithium fraction fLi on glass transition temperature Tg and ionic conductivity σ of lithium borosilicotitanate glasses

Three different lithium borosilicate glass systems with TiO2 addition have been synthesized by melt quenching technique. The XRD was done for all glass samples to confirm their amorphous nature. Electrical conductivity (σ) of these glasses has been studied by dielectric impedance analyzer as a function of frequency at different temperatures in the range 480 to 650 K. Glass transition temperature Tg for the glasses has been determined by using DTA. The density of all glass samples has been determined. It has been observed that the electrical conductivity increases with increasing content of TiO2 which can be attributed to the modification of the structure by the addition of larger titanium ions. It is observed that higher lithium fraction fLi content glass series has highest conductivity. A good correlation is observed between the ionic conductivity, glass transition temperature and lithium fraction of the glasses. The analysis of IR spectra reveals the presence of Ti ions in tetrahedral TiO4 units as well as creation of NBOs, which supports the conductivity results.

Synthesis, characterization and supercapacitor application of ionic liquid incorporated nanocomposites based on SPSU/Silicon dioxide

In this study, we report about novel polymer electrolytes containing sulfonated polysulfone (SPSU) as the polymer matrix, silicon dioxide (SiO2) as nano additive and ionic liquid (1-Ethyl-3-methyl-imidazolium tetrafluoroborate) IL) as a softening agent. In addition, the physical and chemical properties of ionic liquid containing nanocomposite gel polymer electrolytes were studied and subsequently the optimized electrolyte was used to assemble the supercapacitor device. Nanocomposite gel polymer electrolytes demonstrated higher thermal stability and lower glass transition temperatures (Tg) required for supercapacitor application. The ion conductivity of the nanocomposite polymer electrolytes was investigated using a dielectric-impedance analyzer at various temperatures. The highest conductivities were obtained for the samples SPSU/0.1IL and SPSU/%3n SiO2/0.2IL with values 3.1 × 10−4 and 3.2 × 10−3 S cm−1 at 100 °C, respectively. In addition, symmetrical cell formation based on Al/C/SPSU/%3nSiO2/0.2IL/C/Al showed a maximum specific capacitance of 134.1 F g−1 at 1 A g−1. The same cell also yielded a maximum energy density in supercapacitor as 18.6 Wh kg−1 at a power density of 1089 W kg−1.

An investigation of lithium ion conductivity of copolymers based on P(AMPS‐co‐PEGMA)

ABSTRACTIn this work, a series of novel lithium ion‐conducting copolymer electrolytes based on 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and poly(ethyleneglycol) methacrylate (PEGMA) were produced and characterized. The copolymers were synthesized by free‐radical polymerization of the corresponding monomers with three different feed ratios to form P(AMPS‐co‐PEGMA)‐based electrolytes. After the polymerization, AMPS units of the copolymers were lithiated via ion exchange. The characterization of the electrolytes was done by 1H‐NMR, FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy (SEM), and impedance analyzer. The copolymers were thermal stable approximately to 200 °C. Single Tg transitions in DSC curves verified the homogeneity as well as amorphous characteristics. SEM further confirmed the homogeneity of the electrolytes. The lithium ion conductivity of these new polymer electrolytes was studied by impedance dielectric impedance analyzer and the effect of PEGMA contents onto the ionic conductivity of these copolymer electrolytes were investigated. It was observed that the temperature dependence of ionic conductivity was interpreted over Vogel Tammann Fulcher model. The Li ion conductivity increased by PEGMA content and S3 has maximum conductivity of 3 × 10−3 mS cm−1 at 100 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47798.

Boron-incorporated Sulfonated polysulfone/polyphosphoric acid electrolytes for supercapacitor application

ABSTRACTIn the present work, boron-doped multicomponent gel polymer electrolytes composed of host polymer, sulfonated polysulfone (SPSU) and the additives; ionic liquid, 1-ethyl-3-methyl-imidazolium tetrafluoroborate (IL), H3BO3, polyphosphoric acid (PPA) were prepared. Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques were used to characterize the sulfonated polysulfone-based electrolytes. Ion conductivity of these gel electrolytes were studied by dielectric impedance analyzer within the temperature from −20 to 100°C. The ionic conductivity of the SPSU-5IL-1PPA and SPSU-5IL-1H3BO3-1PPA were measured as 4.8 × 10−3 and 9 × 10−4 S cm−1, respectively. Supercapacitor having activated carbon-based composite electrode and electrolyte was constructed with the configuration: Al/C/electrolyte/C/Al. The electrochemical properties and ion transfer characteristics of the supercapacitor were investigated by the cyclic voltammetry (CV). Galvanostatic charge—discharge experiments exhibited good electrochemical reversibility and produced a specific capacitance value of 120 F g−1 at 1 A g−1. The symmetric supercapacitor system was retained almost 85% of its initial activity after 1000 cycle.

Synthesis and anhydrous proton conductivity of doped azole functional PGMA-hBN nano-flakes

A novel approach to produce high temperature stable membranes comprising polymer functional hexagonal boron nitride Nano-Flakes (hBNNF) is proposed. In this context, glycidyl methacrylate was polymerized on the surface of hBNNF via free radical polymerization. 3-amino-1,2,4-triazole and 5-aminotetrazole were chemically linked to polyglycidyl methacrylate (PGMA) over epoxide rings. As prepared, the materials were characterized via Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) with EDX. The results indicated that the yield of the surface polymerization was exceeding 15% (w/w). Anhydrous proton conductivity of azole bound polymer functionalized hBNNF was studied by dielectric impedance analyzer. It was clearly shown that even at low dopant rations; there is a considerable increase in the anhydrous proton conductivity for BN-PGMA-ATet10 reaching to 6 × 10−3 S/cm at 150 °C. In dried state, such conductivity enhancement can be described by Grotthuss mechanism, i.e., structure diffusion.

Single Ion Conducting Blend Polymer Electrolytes Based on LiPAAOB and PPEGMA

Single-ion polymer electrolytes are expected to play an important role in the development of next-generation lithium batteries. The current work focuses on the designing of novel solid single-ion conducting inorganic polymer electrolytes based on lithium polyacrylic acid oxalate borate (LiPAAOB) and poly(ethyleneglycol) methacrylate (PEGMA). PEGMA is polymerized into PPEGMA via free radical polymerization and LiPAAOB is prepared from poly(acrylic acid), oxalic acid and boric acid. Blend polymer electrolytes were produced by mixing of LiPAAOB with PPEGMA at different weight fractions to enhance the single ion conductivity of the system. To exploit the flexible chemistry and increase segmental mobility of the blend electrolyte, the composition was changed up to 80% with respect to PPEGMA. FT-IR and differential scanning calorimeter technique verifies the interaction between the host and guest polymers. Thermogravimetry analysis verified that the thermal stability of the blends increased up to approximately 200 °C. Scanning electron microscopy images confirm the homogeneity of the blend electrolytes. Cyclic voltammetry studies showed that electrochemical stability electrochemical stability window is approximately 5 V versus Li/Li+. The effect of PPEGMA on to the Lithium ion conductivity was investigated using dielectric impedance analyzer. The maximum single ion conductivity was measured as 1.3 × 10−4 S/cm at 100 °C for the sample LiPAAOB-80PPEGMA. Clearly these results confirmed the positive effect to the increment in ionic conductivity of the blend electrolytes with the addition of PPEGMA.

Conductivity and Dielectric Properties of Nearly Monodisperse NiFe 2 O 4 Nanoparticles

Oleylamine (OAm) functionalized NiFe2 O 4 nanoparticles were synthesized by reflux method. Oleylamine as a multufunctional ligand provides the essential basic condition for the formation of NiFe2 O 4 nanoparticles, and it has also surfactant and reducing agent roles. The product was characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry, and thermal gravimetric analyzer (TG). The detailed electrical conductivity and dielectric property of measurements have been performed by dielectric impedance analyzer. The conductivity results show that ac conductivity (σ ac) is temperature dependent particularly at low frequencies whereas dc conductivity (σ dc) exhibits only temperature dependency. The highest dc conductivity is 4.37 × 10 −12 S.cm −1 at 120 ∘C. The dielectric constant (e ′), dielectric loss (e ″), and dielectric loss tangent (tan δ) show different behaviors with frequency and temperature. The variation of dielectric properties with temperature is mainly due to temperature-assisted electron exchange between Ni 2+ and Fe 3+ ions.

Investigation of proton conductivity of PVDF based anhydrous proton exchange membranes (PEMs) obtained via a facile “Grafting Through” strategy

In this work, alkaline treated PVDF was used as a macromolecule in conjunction with GMA in the graft copolymerization. Synthesized PVDF-g-PGMA copolymers were functionalized with 5-aminotetrazole (ATet), and subsequently doped with triflic acid (TA) at several mole ratios with respect to tetrazole units. Finally PVDF-g-PGMA-ATet-(TA)x membranes were fabricated. The composition and the structure of the membranes were characterized by Energy Dispersive X-ray spectroscopy (EDS), 1H-NMR, 19F-NMR and FTIR. According to EDS results, 97 % functionalization with 5-aminotetrazole was achieved. The crystallinity and morphology of the polymers were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Proton conductivity of the materials was investigated by dielectric-impedance analyzer. The proton conductivity increased with increasing temperature and acid doping level. In the absence of humidity, the highest proton conductivity was found as 0.04 S/cm at 150 °C for PVDF-g-PGMA-ATet-(TA)3 membrane. Thermogravimetric analysis (TGA) showed that PVDF-g-PGMA-ATet(TA)3 was thermally stable up to 250 °C. The water uptake of the membranes decreased with triflic acid content. Methanol permeability experiments exhibited that the obtained graft copolymer membranes have similar methanol permeability values with Nafion 112.

Polyimide/tetraethoxysilane-based hybrid polyfilms for microelectronics application

Polyimide (PI) has been extensively investigated as matrix for blends in the search of novel materials for microelectronics and engineering. Tetraethoxysilane (TEOS) is used as precursor for inorganic/organic hybrid material. The processing of PI with TEOS in thin film form offers considerable advantages to the state-of-the art for developing low dielectric constant materials with improved mechanical and hygroscopic properties for microelectronics devices. Taking this into account, the TEOS was incorporated in polyamic acid—a precursor to the PI and a number of properties were evaluated for PI + TEOS films with different concentrations of TEOS. The films prepared with 10−3–10 wt% concentration of TEOS exhibit good overall balance of processing behaviour. The 350°C cured PI + TEOS films have shown lower dielectric constant with respect to PI. The lower dielectric constant of PI + TEOS films, as determined by Dielectric Impedance Analyzer was attributed to the in situ generation of air containing silica domains derived from TEOS dispersed within the PI matrix in nano meter regime. FTIR analysis has confirmed the generation of silica while AFM analysis showed the distinct appearance of silica domains dispersed into the PI matrix. The mechanical properties were evaluated by Universal Testing Machine on PI and PI/TEOS films. The films with 10−3–1 wt% composition of TEOS showed enhancement in overall mechanical properties while higher concentration i.e. 5 and 10 wt% of TEOS containing PI showed deterioration with respect to pure PI. The water absorption isotherms were measured and their absorption behaviour was correlated with dielectric constant and associated morphology.

Intergrain connectivity of MgB2 ceramics studied by impedance analysis

First, by using of the conventional Rowell analysis, we demonstrated that the addition of nano BN particles can effectively eliminate MgO and pores in MgB2 resulting in a very high density and good connectivity of BN-doped MgB2. Then, another method—low-frequency dielectric impedance analysis—was introduced to characterize the properties of the grain boundaries of MgB2. A comparative impedance study was performed in the frequency range from 100 Hz to 100 MHz on pure and nano BN-doped MgB2. The study revealed some following interesting results: (1) a dielectric resonance around frequency of 108 in both samples was observed, which was argued to be related to an inductance-capacitance and (2) the pure sample has two dielectric relaxations originating from intergrains, while the doped sample has only one intergranular contribution. This convinces that the electric connectivity of the doped sample is really improved by the addition of nano BN particles. Our results indicate that dielectric technique may be a useful tool to characterize the grain boundary properties and grain boundary-related properties of MgB2.

Optical characterization of ferroelectric glycinium phosphite single crystals

Single crystals of glycinium phosphite (GPI) were grown by isothermal evaporation and conventional temperature-lowering techniques. Single crystal and powder X-ray diffraction analysis confirm the monoclinic structure of the as grown crystals. The structural perfection of the as grown crystal was determined through HRXRD analysis. FTIR and Raman analysis revealed the functional groups present in the grown crystals. The optical absorption of the grown crystal was analyzed and the refractive index values for different wavelengths were measured by prism coupling technique. Thermal stability, melting temperature and phase transition temperature of the as grown crystals were identified from TGA/DSC analysis. The dielectric impedance analysis indicates the continuous phase transition nature of the grown crystals. The mechanical strength and hardening co-efficient were determined from Vicker's microhardness measurements for different loads with constant dwell time. The growth mechanism and the defects were analyzed through chemical etching analysis from various crystallographic planes and etching periods.