Preparation,characterization and dielectric properties of polyetherimide nanocomposites containing surface‐functionalized BaTiO3 nanoparticles

Polyetherimide (PEI)/hydroxyl‐functionalized barium titanate (BaTiO₃) nanocomposite films were successfully prepared through solution‐casting followed by subsequent thermal imidization. The results of Fourier transform infrared spectroscopy confirmed that the chemical treatment with hydrogen peroxide (H₂O₂) could efficiently derive hydroxyl groups on the surface of BaTiO₃ nanoparticles. The strong interaction between the hydroxyl‐functionalized BaTiO₃ and the PEI matrix greatly enhanced the particle dispersion as well as the interfacial adhesion, as evidenced by scanning electron microscopy. The PEI nanocomposite with hydroxyl‐functionalized BaTiO₃ nanoparticles (50 vol% BaTiO₃ loading) showed an increased dielectric permittivity of 52.78 at 1 kHz compared with the dielectric permittivity (33.87) of PEI/raw BaTiO₃ composite. The loss tangent was still low (less than 0.03) when the content of hydroxyl‐functionalized BaTiO₃ was 50 vol%. For PEI/BaTiO₃ nanocomposites, the frequency and temperature dependences of the dielectric properties were significantly reduced through functionalizing the surface of BaTiO₃ nanoparticles with H₂O₂. Different theoretical approaches were employed to predict the effective permittivity of the nanocomposite systems and the results are compared with the experimental results. Copyright © 2012 Society of Chemical Industry     

Dielectric performance of composites of BaTiO3 and polymers for capacitor applications under microwave frequency

Composites of nano-sized barium titanate (BaTiO₃) with volume fractions up to 0.5 and poly(butylene terephthalate) (PBT) or linear low-density polyethylene (LLDPE) were made via extrusion. Scanning electron microscopy demonstrated that BaTiO₃ is well dispersed in the polymer matrices. The crystalline content (DSC) and thermal stability (TGA) of both polymers decreased with increasing BaTiO₃ loading. Dielectric properties of the composites were measured using a vector network analyzer. Both dielectric permittivity and tangent loss increased with increasing BaTiO₃ content. At 2.45 GHz, the dielectric permittivity for 48 vol% BaTiO₃-filled LLDPE and 43 vol% BaTiO₃-filled PBT was 25 and 21.2, respectively. There was a good fit between the Lichtenecker model and experimental data obtained up to a certain value, with the permittivity variations being dependent on volume fraction. The improved dielectric performance achieved on inclusion of BaTiO₃ confirms both composite systems as potential candidates for microwave frequency capacitor applications.     

Nanocomposites of Surface‐Modified BaTiO3 Nanoparticles Filled Ferroelectric Polymer with Enhanced Energy Density

We report nanocomposites of increased dielectric permittivity, enhanced electric breakdown strength and high‐energy density based on surface‐modified BaTiO₃ (BT) nanoparticles filled poly(vinylidene fluoride) polymer. Polyvinylprrolidone (PVP) is used as the surface modification agent and homogeneous nanocomposite films have been prepared by solution casting processing. The dielectric permittivity of the nanocomposite with treated BT is higher than those with untreated BT and reaches the maximum value of 77 (1 kHz) at BT concentration of 55 vol%. The electric breakdown strength of the nanocomposite is greatly enhanced to 336 MV/m at BT concentration of 10 vol% and the calculated energy density is 6.8 J/cm³. The results indicate that using PVP as surface modification agent can greatly enhance the dielectric permittivity and electric breakdown strength of the ceramic–polymer nanocomposite and achieve high‐energy density for energy storage and power capacitor applications.     

Impact of BaTiO3 as insulative ferroelectric barrier on the broadband dielectric properties of MWCNT/PVDF nanocomposites

This study was devoted to investigating the effects of BaTiO₃ incorporation on the broadband dielectric properties of melt‐mixed multi‐walled carbon nanotube/poly(vinylidene fluoride) (MWCNT/PVDF) nanocomposites. BaTiO₃, as insulative barrier, was incorporated into the composites with MWCNT loadings close to and above the percolation threshold, where conductive networks were unstable and newly formed. The results showed that BaTiO₃ did not create any change in the volume resistivity and percolation curve; nevertheless, it reduced the dissipation factor considerably. For instance, at 100 Hz the dissipation factor of the MWCNT/PVDF nanocomposite was 130, which dropped to 48 and 0.45 by adding 1.0 and 3.0 vol% BaTiO₃, respectively. It was also observed that incorporating BaTiO₃ muted the descending trends of dielectric permittivity and dielectric loss with frequency, confirming the role of BaTiO₃ as insulative barrier. The positive impact of BaTiO₃ on the dielectric properties of the MWCNT/PVDF nanocomposites was attributed to deteriorated conductive network. POLYM. COMPOS., 299–304, 2016. © 2014 Society of Plastics Engineers     

Microstructure and dielectric properties of Ag-BaTiO3 composite ceramics

Di-phase composite ceramics based on BaTiO₃ with 5?vol% of Ag filler have been prepared by sintering the mixture of powders at temperatures above the silver melting point (1000?°C–1300?°C/2?h). As predicted by finite element calculations, the addition of metallic particles should produce a field concentration in some regions of the BaTiO₃ matrix and therefore, an enhanced dielectric response with respect to pure BaTiO₃. The role of oxygen vacancies on the dielectric relaxation mechanisms of Ag-BaTiO₃ composites has been investigated. The sintering temperature of 1200?°C provided optimized ceramics with excellent dielectric properties, i.e. with low losses (tanδ?<?3%) and room temperature permittivity measured at 50?kHz exceeding 6500 (and above 13,000 at the Curie temperature), as result of a good densification (94% relative density) and a synergy effect of the metallic particles inclusions and ceramic grain size in the range of ≈1?μm, where BaTiO₃ has a well-known maximum of its permittivity.     

Microstructural evolution and electric properties of mechanically activated BaTiO3 ceramics

Ceramic materials with a perovskite related structures such as non-doped and doped barium titanate ceramics are attracting much interest for their application as capacitor dielectrics, resistors, thermal sensors, etc. Since mechanical activation can be used in order to modify properties of these materials, in this study microstructure evolution and electric properties of mechanically activated BaTiO₃ have been analyzed. The sintering process of high purity non-doped mechanically activated BaTiO₃ was monitored using a sensitive dilatometer with a heating rate of 10 °C/min. Investigation of the microstructure evolution of mechanically activated BaTiO₃ was performed using scanning electron microscope (SEM) and digital pattern recognition (DPR) methods. A dielectric study of the paraelectric–ferroelectric phase transition in the barium titanate ceramics was performed by recording the temperature dependence of dielectric permittivity.     

Simultaneous enhancement of dielectric properties and temperature stability in BaTiO3-based ceramics enabling X8R multilayer ceramic capacitor

Modified BaTiO₃ ceramics that possess high dielectric permittivity and acceptable temperature stability have been widely utilized as multilayer ceramic capacitors (MLCCs) for high-frequency bypass and power filtering in automotive applications. However, since the increasing demand for high-capacity and small-size, high-permittivity materials that can serve as dielectric layers in MLCCs are urgently required. In this work, we design and fabricate a special BaTiO₃-0.03Mg-0.02Y-0.02CaZrO₃ ceramic with a high dielectric permittivity of 3000 and the dielectric variation below ±13% in the temperature range of -55–150°C, fulfilling the requirements of X8R capacitors. To achieve these results, we employed grain size engineering and cation doping, using BaTiO₃ precursors with a particle size of 240 nm to prepare the BaTiO₃-based ceramics with fine grains, while Mg and Y co-doping was used for improving the temperature stability due to dielectric dispersion. Utilizing these high-permittivity BaTiO₃-based materials, we fabricated MLCCs that satisfy the X8R criterion, possessing a high dielectric constant of 2950 and a high breakdown field (410 kV/cm).     

Fabrication of BaTiO3-PTFE composite film for embedded capacitor employing aerosol deposition

The potential for using aerosol deposition (AD) as an alternative fabrication method to the conventional polymer composite process for embedded capacitors was examined. In order to achieve a high relative dielectric permittivity, BaTiO₃-polytetrafluoroethylene (PTFE) composite thick films were attempted by AD at room temperature. For the high dielectric constant, the BaTiO₃-PTFE composite films grown by AD should satisfied the following two critical conditions: a reduced decrement in ceramic particle size and a relieved distortion of the crystal structure. However, the relative permitivity of the composite films was too low compared with that of the BaTiO₃ films grown by AD. By predicting the dielectric constant in several composite models using the Hashin-Shtrikman bounds theory and 3-dimenstional (3-D) electrostatic simulation, we confirmed that the connectivity between ceramic particles is a highly critical factor for achieving a high dielectric constant in composite films.     

Good dielectric performance and broadband dielectric polarization in Ag,Nb co-doped TiO2

Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO₂-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag⁺/Nb⁵⁺ co-doped (Ag_1/4Nb_3/4)_xTi_1−xO₂ (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 10³ and 1.6 × 10⁴ at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics.     

Embedded Capacitor Technology Using Aerosol Deposition

Embedded passives, which achieve miniaturization, cost reduction, and higher performance, are regarded as one of the most promising technologies for a future RF module substrate. Currently, a BaTiO₃/Polymer composite is being used for the embedded capacitors in printed wiring boards. One of the drawbacks of this composite is its relatively low dielectric constant, because the polymer component with a low dielectric constant suppresses the dielectric constant of the whole composite. We propose a resin build-up circuit board with passive functions embedded in a ceramic film without any polymer component for the next-generation low-cost RF modules. We have already manufactured a prototype board with ceramic capacitors embedded in an FR-4 substrate using a unique ceramic deposition technology: aerosol deposition (ASD) in which many kinds of ceramics can be deposited on a substrate at room temperature by making use of accelerated ceramic nanoparticle aerosol bombardment with a nozzle. In this study, first we examine the effects of the characteristics of raw ceramic powder on the crystal structure and the dielectric properties of ASD films. As a result, we confirmed that dense BaTiO₃ dielectric films can be deposited when raw powder without strain is used. From the resulting polarization versus electrical field (P–E curve), we confirmed that paraelectric was observed in the dense films, while the porous BaTiO₃ films deposited using milled powder exhibit a small hysteresis loop. We also clarified that dense BaTiO₃ dielectric films exhibit a nanostructure with a texture consisting of particles under 10 nm in diameter. We also examine the interfacial behavior between BaTiO₃ dielectric films and the Cu electrode, in order to investigate the deposition temperature and the reliability of a BaTiO₃ ASD film under high temperature (250°C), high humidity (100 Rh%), thermal cycle condition (−55°C to 150°C), and bias DC voltage (5 V). We clarified that the BaTiO₃ ASD film satisfies the criteria of reliability in the microelectronic packaging area.     

High permittivity BaTiO3 and BaTiO3-polymer nanocomposites enabled by cold sintering with a new transient chemistry: Ba(OH)2∙8H2O

Cold sintering process (CSP) offers a promising strategy for the fabrication of innovative and advanced high permittivity dielectric nanocomposite materials. Here, we introduce Ba(OH)₂?8H₂O hydrated flux as a new transient chemistry that enables the densification of BaTiO₃ in a single step at a temperature as low as 150 °C. This remarkably low temperature is near its Curie transition of 125 °C, associated with a displacive phase transition. The cold sintered BaTiO₃ shows a relative density of 95 % and a room temperature relative permittivity over 1000. This new hydrated flux permits the fabrication of a unique dense BaTiO₃-polymer nanocomposite with a high volume fraction of ceramics ((1-x) BaTiO₃ – x PTFE, with x = 0.05). The composite exhibits a relative permittivity of approximately 800, at least an order of magnitude higher than previous reports on polymer composites with BaTiO₃ nanoparticle fillers that are typically well below 100. Unique high permittivity dielectric nanocomposites with enhanced resistivities can now be designed using polymers to engineer grain boundaries and CSP as a processing method opening up new possibilities in dielectric materials design.     

Processing,Dynamic mechanical thermal analysis,and dielectric properties of barium titanate/cellulosic polymer nanocomposites

High dielectric constant BaTiO₃/ethyl cellulose (BT/EC) nanocomposites having BT loadings of up to 13 vol% were fabricated through a simple casting technique. The BT filler powder, synthesized through an ultrasonic‐assisted solid‐state route, was revealed by X‐ray powder diffractometry (XRD) and Raman spectroscopy to be dominantly tetragonal. Scanning electron microscopy (SEM) showed good dispersion of the BT nanoparticles in the EC polymer matrix at lower BT concentrations. However, at higher concentrations, the BT particles form a continuous phase or a “filler network” leading to weak BT/EC interactions. This finding is well supported by the results of the tensile strength and storage modulus. The dielectric properties of the BT/EC nanocomposites were investigated over wide ranges of frequency and temperature. The addition of BT significantly increased the permittivity (ε ′) and dielectric loss (ε ″) and improved the ionic conductivity of the EC. The electric modulus (M″ ) results were analyzed in terms of the Havriliak–Negami function through three distinct relaxation mechanisms (namely α, β*, and β relaxations) in the temperature range 30–150°C. The dc conductivity (σ _dc) results suggest that the BT/EC nanocomposites formed at low BT loading (up to 7.0 vol%) and a temperature of ≤60°C are good candidates for antistatic applications while those formed at higher concentrations and temperatures are recommended for use in electrostatic dissipation applications. POLYM. COMPOS., 38:893–907, 2017. © 2015 Society of Plastics Engineers     

Polyimide dielectric nanocomposites containing functional nanofillers based on multilayer structure: Design,preparation, and properties

Polyimide (PI) dielectric nanocomposites containing functional nanofillers based on layered structure (single-layer: BT@Al₂O₃@PI, double-layer: PI/BT@Al₂O₃@PI, three-layer: PI/BT@Al₂O₃@PI/PI) were designed and prepared by using PI as matrix, barium titanate (BT)@alumina (Al₂O₃) as nanofillers through in-situ polymerization compounding technology. FTIR tests indicated that PI and PI dielectric nanocomposites have been synthesized successfully. The molecular mass of BaTiO₃@Al₂O₃@PAA oligomer was higher than that of pure PAA when BT and Al₂O₃ nanofillers were incorporated simultaneously, as verified by GPC and intrinsic viscosity tests. XRD analysis showed that the addition of nanofillers destroyed the order of PI molecular structure and reduced the arrangement density of PI molecular chains. Both FESEM and HRTEM observations showed that the nanofillers were homogeneously dispersed in the PI matrix, contributing to the property improvements of PI dielectric nanocomposites. TGA results indicated that adding nanofillers improved the thermal stability and heat resistance of PI dielectric nanocomposites. The dielectric constant of PI/BT@Al₂O₃@PI double-layer nanocomposites was between the single-layer nanocomposites and pure PI. Due to the effective medium theory, the dielectric constant of three-layer PI/BT@Al₂O₃@PI/PI nanocomposites containing 5 wt% BT@Al₂O₃ reached 5.43. This work can be expected to provide an effective strategy to fabricate PI dielectric nanocomposite films for energy storage applications.     

Barium titanate‐based nanodielectrics of two chemically recyclable thermosets

In this work was investigated the effect of the addition of barium titanate (BaTiO₃) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO₃‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10^?8 S m^?1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO₃ ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (10² Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (T_g) values in the range 125–180 °C. An increase of 7 °C in T_g was observed after the incorporation of 0.5 wt% of BaTiO₃ into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO₃. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry     

Flexible 0–3 Ceramic‐Polymer Composites of Barium Titanate and Epoxidized Natural Rubber

Flexible composites with a high electrical permittivity are pursued in materials research, due to their potential applications in electrical devices. We synthesized such ceramic‐polymer composites from BaTiO₃ and epoxidized natural rubber. The influence of BaTiO₃ concentration on cure characteristics, mechanical (static & dynamic), dielectric, and morphological properties of the composites was investigated. The tensile strength and elongation at break decreased with BaTiO₃ loading, while the storage modulus and permittivity of composites increased. As for dynamic electrical properties, the dielectric loss factor and tan δ of the composites showed a maximum peak within the frequency range extending up to 10⁵ Hz, reflecting the relaxation process of the polymer matrix. All of the composites showed two peaks in the frequency dependence of electric modulus, due to conductivity and molecular relaxation. Scanning electron microscopy micrographs confirmed the 0–3 structure of composites, with isolated BaTiO₃ particles.     

Improved dielectric properties and energy density of PVDF composites using PVP engineered BaTiO<Subscript>3</Subscript> nanoparticles

This work systematically investigates the effect of modifier polyvinylpyrrolidone (PVP) on the microstructure, dielectric and energy storage properties of BaTiO₃/PVDF composites. The results demonstrate that the BaTiO₃ nanoparticles modified by PVP are uniformly dispersed in the composites, and the defects including cracks and voids are obviously decreased in contrast to the composites with unmodified BaTiO₃ nanoparticles. Due to the enhanced interfacial polarization, the composites with BaTiO₃@PVP show improved dielectric properties compared with the composites with unmodified BaTiO₃ nanoparticles. For instance, at 1 kHz, the dielectric constant and dielectric loss of the composite with 50 vol% of BaTiO₃@PVP nanoparticles are 80.4 and 0.085, while of which the BaTiO₃/PVDF are 35 and 0.265, respectively. The discharge energy density of the composites is largely improved with PVP engineered BaTiO₃ nanoparticles. The composite with 30 vol% BaTiO₃@PVP achieves a discharged energy density of 4.06 J/cc at 240 kV/mm, which is 116% larger than that of pure PVDF (1.88 J/cc). This research provides an effect modifier to prepare high performance dielectric materials.     

Dielectric properties of polyethylene terephthalate/polyphenylene sulfide/barium titanate nanocomposite for application in electronic industry

Polymer/ceramic nanocomposites designed for application as electronic packaging were prepared using corotating twin‐screw extruder. The dielectric properties of the composites made from polyethylene terephthalate (PET), polyphenylene sulfide, and barium titanate were studied as a function of BaTiO₃ fraction in the range between 0.75 and 1.5 wt%. Processing parameters were optimized in order to obtain the nanocomposites with appropriate dielectric properties like dielectric permittivity ε′, dielectric losses ε″, and their temperature stability in a wide frequency range. The measurements showed the increase of the dielectric permittivity value ε′ in the composites in comparison to both pure polymers. The dielectric loss factor tgδ of the composites was found to be much smaller than that of the pure PET. The weak influence of the ceramics on the temperature stability of the dielectric properties of the composites was stated. POLYM. ENG. SCI., 50:1613–1619, 2010. © 2010 Society of Plastics Engineers     

Duplex structure in K0.5Na0.5NbO3-SrZrO3 ceramics with temperature-stable dielectric properties

Temperature-stable dielectric properties have been developed in the 0.86 K_0.5Na_0.5NbO₃-0.14SrZrO₃ solid solution system. High dielectric permittivity (ε′ = 2310) with low loss sustained in a broad temperature range (−55–201 °C), which was close to that of the commercial BaTiO₃-based high-temperature capacitors. Transmission electron microscopy with energy dispersive X-ray analysis directly revealed that submicron grains exhibited duplex core-shell structure. The outer shell region was similar to the target composition, whilst a slightly poor content of Sr and Zr presented in the core region. Based on Lichtenecker’s effective dielectric function analysis along with Lorentz fit of the temperature dependence of dielectric permittivity, a plausible mechanism explaining the temperature-stable dielectric response in present work was suggested. These results offer an opportunity to achieve the X8 R specification high-temperature capacitors in K_0.5Na_0.5NbO₃ based materials.     

Enhanced dielectric permittivity of BaTiO3/epoxy resin composites by particle alignment

Barium titanate (BaTiO₃)/epoxy resin composites with a novel structure, in which the BaTiO₃ particles were directionally aligned in the epoxy resin matrix, were fabricated using the ice-templating method. The effects of the filler particle alignment and the filler fraction on the dielectric permittivity as well as the dielectric loss of the composites were studied. The results show that the aligning filler particles can significantly improve the dielectric permittivity while maintaining the dielectric loss compared with the traditional composite structure (homogeneously distributed). Due to the feasibility of the enhancement of the dielectric properties of the composites, the particle alignment that is achieved via the ice-templating method can be used in the field of high energy density capacitors.     

Improvement of high-temperature energy storage properties of polyimide-based nanocomposites with sandwich structure

The demand for dielectric materials that have high energy and power density properties, and are operational at high temperature has increased with the advancement in new energy technology, high-end microelectronics, and other industries. Pure ceramic and polymer capacitors are not enough to meet the ever increasing energy requirements in a wide range of applications. In this article, we report a sandwich structure nanocomposite film based on polyimide (PI) with high breakdown strength SiO₂/PI as the outer layers and high dielectric constant strontium titanate (SrTiO₃)/PI as the sandwich layer. The results showed that the prepared composites can obtain high energy storage density and low dielectric loss at high temperatures. The composites achieved an energy storage density of 5.5 J cm⁻³ and a dielectric loss of 0.004 at a temperature of 150°C when the filling amount of SrTiO₃ was 0.5 vol% and the filling amount of SiO₂ was 3 vol%. This work shows that the composites are promising dielectrics for applications at high temperature and provides a new idea for high-temperature energy storage devices.