Dielectric properties of BaTiO<Subscript>3</Subscript>/epoxy composites by lamination process for embedded capacitor application

Because of the fabricability of polymer and excellent dielectric properties of ceramics, ceramic-polymer composites have been investigated widely for embedded capacitors which can improve electric performance greatly. In order to obtain further application of composite, the embedded capacitors with three-layer sandwich structure containing the BaTiO₃/epoxy composites as dielectric layer and copper foil as electrodes were fabricated. The dielectric properties are improved by preventing the defect in dielectric layer through lamination process. Our results show that the capacitors exhibit high dielectric permittivity (ε = 20), low dielectric loss (0.01) at 10³ Hz from 40 to 100 °C and high breakdown strength (24 kV/mm), which indicate that the lamination is a promising process for embedded capacitor fabrication and BaTiO₃/epoxy composites have potential for high-performance embedded capacitors application in field of microelectronics.     

Properties of calcium copper titanate and barium titanate filled epoxy composites for electronic applications: effect of filler loading and hybrid fillers

Inorganic ceramics such as calcium copper titanate, CaCu₃Ti₄O₁₂ (CCTO) and barium titanate (BaTiO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler types and loading range on the dielectric, tensile, morphology, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin film composites with 20 vol% filler loading of CCTO and BaTiO₃ showed good dielectric properties, thermal stability, and thermal conductivity. However, the tensile properties of the CCTO/epoxy thin film composite was reduced as the filler loading increased. On the other hand, the tensile properties of BaTiO₃/epoxy thin film composite improved as the filler loading increased. Hybrid fillers CCTO and BaTiO₃ filled epoxy composites were fabricated and the effect of hybrid fillers on the dielectric properties and morphology of the epoxy thin film composites were investigated. Results indicated that positive hybrid effect in dielectric constant and dielectric loss showed by the hybrid composites.     

Ceramic/natural rubber composites: influence types of rubber and ceramic materials on curing,mechanical, morphological,and dielectric properties

Influence of different types of rubber and ceramic material on cure characteristics, mechanical, morphological, and dielectric properties of natural rubber (NR) vulcanizate was studied. Two types of ferroelectric ceramic materials: barium titanate (BaTiO₃) and lead titanate (PbTiO₃) were prepared by solid-state reaction with calcinations at 1100 °C for 2 h. The ceramic powders were then characterized by X-ray diffraction (XRD), particle size analyzer, and SEM techniques. Ceramic/rubber composites were then prepared by melt mixing of rubber and ceramic powders. Two different types of NR (i.e., epoxidized NR [ENR] and unmodified NR) and two types of ceramic powders (i.e., BaTiO₃ and PbTiO₃) were exploited. It was found that incorporation of ceramic powders in rubber matrix and the presence of epoxirane rings in ENR molecules caused faster curing reaction, and higher delta torque but lower elongation at break. This is attributed to lower mobility of molecular chains and higher interaction between ENR molecules. Furthermore, SEM results revealed that the BaTiO₃ composites showed finer and better distribution of the particles in the rubber matrix than that of the PbTiO₃ composite. This caused superior mechanical properties of the BaTiO₃ composites. Furthermore, higher dielectric constant and loss tangent was observed in the ENR/BaTiO₃ composites.     

Three-phase polymer–ceramic–metal composite for embedded capacitor applications

This paper addresses the materials and processes for printed wiring board compatible embedded capacitor using ceramic, polymer and metal. The Ca[(Li_1/3Nb_2/3)_0.8Ti_0.2]O_3?δ (CLNT)–epoxy–silver, three-phase composites were prepared by two step mixing and thermosetting technique. The dielectric properties of the three-phase composites were investigated in terms of volume fraction of silver, temperature and frequency. The dielectric properties of epoxy–CLNT composites were compared with theoretical predictions. The relative permittivity of the three-phase composites increased with silver loading. Addition of 0.28 volume fraction of silver increases the relative permittivity of epoxy–CLNT composites from 8 to 142 at 1 MHz. This composite is flexible and can be fabricated into various shapes with low processing temperature.     

Dielectric behavior of CCTO/epoxy and Al-CCTO/epoxy composites

A composite of epoxy embedded with a giant dielectric constant material CaCu₃Ti₄O₁₂ (CCTO) was fabricated. Various theoretical models were employed to rationalize the dielectric behavior of these biphasic composites. Amongst different models that were employed to predict the dielectric properties of the composites, the effective dielectric constants (ε_eff), obtained via Yamada model were in close agreement with the experimental values. A metallic inclusion in CCTO/epoxy composite was found to be effective way to enhance its dielectric constant. A three phase percolative composite (Al-CCTO/epoxy) was fabricated and percolation theory was employed to describe its dielectric behavior.     

Dielectric and ferromagnetic properties of BaTiO<Subscript>3</Subscript>/Ni<Subscript>0.93</Subscript>Co<Subscript>0.02</Subscript>Cu<Subscript>0.05</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> composites

xBaTiO₃ + (1 − x)Ni_0.93Co_0.02Cu_0.05Fe₂O₄ (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to 15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation magnetization (M _s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric materials.     

Tensile,dielectric, and thermal properties of epoxy composites filled with silica,mica, and calcium carbonate

The minerals silica, mica, and calcium carbonate (CaCO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler loading and type on the morphology, tensile, dielectric, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin films with 20 vol% filler loading showed good dielectric properties, thermal conductivity, and thermal stability. However, the tensile properties of the thin films were reduced as the filler loading was increased due to brittleness. Dielectric constant and dielectric loss of epoxy/inorganic composite films generally increased with increasing mineral filler loading. Meanwhile, the presence of mineral filler improved the thermal stability of the thin film composites. The highest dielectric constant of 5.75 with 20 vol% filler loading at a frequency of 1 MHz was exhibited by the epoxy/CaCO₃ composite, followed by epoxy/mica and epoxy/silica. Therefore, the epoxy/CaCO₃ composite is the most potential candidate for capacitor application. Moreover, precipitated CaCO₃ provided better tensile properties and slightly improved the dielectric properties compared with mineral CaCO₃.     

Dielectric response of Ag/BaTiO<Subscript>3</Subscript>/epoxy nanocomposites

Dielectric properties and relaxation phenomena of hybrid material (functionalized nanosilver/BaTiO₃/epoxy) were studied as a function of ceramic content. Nanoparticles were obtained through chemical reduction in ethanol and triethylenetetramine. Epoxy resin, functionalized Ag and BaTiO₃ were mixed and composites were prepared onto glass substrates by dipping technique. Samples containing various amounts of ceramic filler were examined by thermal and SEM analysis. Dielectric measurements were performed at different frequencies and temperatures. It was found that hybrid materials had high permittivities and their relaxation processes were influenced by the epoxy resin near its T _g, while metallic and ceramic content modified the real permittivity values.     

Effect of filler size and concentration on the structure and properties of poly(vinylidene fluoride)/BaTiO<Subscript>3</Subscript> nanocomposites

The effect of filler size and content in the thermal, mechanical, and electrical response of poly(vinylidene fluoride) (PVDF)/BaTiO₃ nanocomposites has been investigated. Dielectric constant increases significantly with increasing filler content and decreasing filler size. Space charge effects at the interface between BaTiO₃ and PVDF strongly influence the dielectric response. The electroactive β-phase of PVDF is nucleated by the presence of the ceramic filler, the effect being strongly dependent on filler size and independent on filler content. This filler/matrix interaction is also responsible for the variations observed in the activation energy of the thermal degradation of the polymer. Smaller particles lead to larger relative contact areas and are responsible for the main variations observed in the thermal, mechanical, and electrical properties of the composites.     

Effect of the dispersibility of BaTiO3 nanoparticles in BaTiO3/polyimide composites on the dielectric properties

We have investigated the effect of coupling agents with different organic moiety on the dielectric properties of polyimide/BaTiO₃ (70 nm) composite films. INAAT (isopropyl tris(N-amino-ethyl aminoethyl)titanate, KR 44) and APTS (3-amino-propyl-triethoxysilane) were used as coupling agents, respectively, for homogeneous dispersion of BaTiO₃ particles into a polyimide matrix. The composite films were prepared by pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA)-based polyimide. Enhanced dispersion of BaTiO₃ particles was obtained by the use of INAAT with more organic moiety compared to that afforded by APTS. The polyimide composite with BaTiO₃ particles (BaTiO₃ content at 50 vol.%) treated by INAAT showed an increased dielectric constant of 19.03 while retaining an appropriate dielectric loss of 0.0109, as compared to the dielectric constant (14.64) of polyimide/APTS-treated BaTiO₃ composite. The results of this work demonstrate the potential use of an INAAT coupling agent with more organo functional groups for obtaining enhanced dielectric properties in a polyimide/BaTiO₃ composite for application in an embedded capacitor.     

Investigation on FT-IR spectra and dielectric property of PVDF/inorganic composites

In order to explore the effects of ceramics’ contents on composites’ macro-performance and microscopic structure, polyvinylidene fluoride/barium titanate composites were prepared by a coating technique. The PVDF/BaTiO₃ (Bi₄Ti₃O₁₂) composites are selected as research objects. It was observed that BaTiO₃ (Bi₄Ti₃O₁₂) powders with different ceramics’ contents affected the performance of PVDF/BaTiO₃ (Bi₄Ti₃O₁₂) composites’ dielectric. As the content of inorganic powders increases in some extent, dielectric constant of PVDF/inorganic powder composites increases. The microscopic structures of the materials were further studied. A red-shift was observed by Fourier transform infrared spectroscopy (FT-IR). Results of X-ray diffraction and FT-IR on PVDF/BaTiO₃ showed that both the physical role (induction of β phase and interface defect) and the chemical bonding effect between BaTiO₃ and PVDF affect the dielectric property of the composites. The chemical bonding effect was also observed in PVDF/Bi₄Ti₃O₁₂ composites by FT-IR. Our results suggest that the intercoupling between fluorine in polyvinylidene fluoride and oxygen vacancy in barium titanates plays an important role in this kind of ferroelectric organic–inorganic composites. Overall, this paper provides some new and useful insights about the relationship between the physical property of PVDF/ceramic composites’ and composites’ microscopic structure.     

机载龙伯透镜天线用聚苯乙烯泡沫塑料的制备及介电常数调控

针对雷达通讯微波频段新型轻质介电复合材料的迫切需求,开展高介电性能复合材料的研究具有现实意义。采用悬浮聚合法制备不同密度的聚苯乙烯泡沫,研究了聚苯乙烯泡沫的介电常数与密度之间的关系,分析了钛酸钡粉末的介电性能。采用干混法添加钛酸钡粉末制备介电常数可调控的轻质钛酸钡/聚苯乙烯复合泡沫。聚苯乙烯泡沫的介电常数随密度增大,表现出弱的频率依赖性和低介电损耗。钛酸钡粉末具有高的介电常数和较低的介电损耗。BaTiO_3/PS复合材料的介电常数随着BaTiO_3含量的增加而升高。相同介电常数的BaTiO_3/PS复合材料和聚苯乙烯泡沫相比,密度显著下降,说明添加BaTiO_3可以实现介电材料的轻质化。     

Electric properties of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript>(BIT)–CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> (CCTO) composite substrates for high dielectric constant devices

A study of the effect of the presence of BIT (Bi₄Ti₃O₁₂) in the dielectric and optical properties of the CaCu₃Ti₄O₁₂ (CCTO) is presented. The samples were prepared by the solid state procedure. Mechanical alloying followed by the solid state procedure has been used successfully to produce powders of CaCu₃Ti₄O₁₂ (CCTO) and BIT (Bi₄Ti₃O₁₂) to be used in the composites. We also look at the effect of the grain size of the BIT and CCTO in the final properties of the composite. The samples were studied using X-Ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopy. We also did a study of the dielectric function K and dielectric loss of the samples. The role played by the grain size of CCTO and BIT in the dielectric constant and structural properties of the substrates are discussed. For frequencies below 10 MHz the K value presented by the CCTO100 sample is always higher than the K value presented by the BIT100 sample. At 100 Hz the value of K 1900 for the CCTO100 sample and 288 for the BIT100 sample. However for the composite sample one has an unexpected result. The dielectric constant is higher for all the frequencies under study. At 100 Hz the value of the K is around 10.000 for the BIT10 sample. Which is more than one order bigger compared to the CCTO100 value for the same frequency. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These composites are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones for example), where the miniaturization of the devices is crucial.     

Effects of (Na<Subscript>1/2</Subscript>Nd<Subscript>1/2</Subscript>)TiO<Subscript>3</Subscript> on the microstructure and microwave dielectric properties of PTFE/ceramic composites

A study on polytetrafluoroethylene (PTFE) composites with Na_1/2Nd_1/2TiO₃ (NNT) ceramic and E glass shorten fiber (E-GF) was described. The E-GF content was fixed at 5 wt.%, and the NNT content varied from 12.1 vol.% to 42.8 vol.%. This paper systematically introduced the preparation process of composites and the effects of NNT filling content on the properties of composites. The surface modification of ceramic powders was observed by Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), which proved that NNT surfaces have been modified by Perfluorooctyltriethoxysilane (F8261) successfully. When the NNT filling content was 42.8 vol.%, substrate material with a low water absorption of 0.12%, high dielectric constant of 9.45, low dielectric loss of 0.0024, and τ_ε of -222 ppm/°C were achieved, which is of great reference significance for the miniaturization and integration of microwave devices.     

Dielectric properties of Pb(Zn<Subscript>1/3</Subscript>Ta<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-introduced (Ba,Pb)TiO<Subscript>3</Subscript> ceramic system

Ceramic powders of the Pb(Zn_1/3Ta_2/3)O₃-introduced BaTiO₃–PbTiO₃ system were prepared using a B-site precursor method. Perovskite formation tendencies of the system compositions were determined by X-ray diffraction. Weak-field low-frequency dielectric properties of the sintered ceramics were investigated. Dielectric constant spectra were further analyzed in terms of diffuseness. Internal microstructures of the ceramics were also examined.     

Preparation and microwave characterization of BaWO<Subscript>4</Subscript> filled polytetrafluoroethylene laminates for microwave substrate applications

Phase pure BaWO₄ ceramic filler has been prepared through solid state ceramic route. Planar BaWO₄ filled Polytetrafluoroethylene (PTFE) composite substrates were fabricated through Sigma Mixing (SM), Extrusion (E), Calendering (C) followed by Hot pressing (H) (SMECH) processes. Morphology and filler distribution of the composites were analyzed using particle size analysis and scanning electron microscopy. The effect of BaWO₄ ceramic filler content on the dielectric properties of the composites was measured at microwave frequency using X-band waveguide cavity perturbation technique. Optimum BaWO₄ filler loading in the PTFE matrix has been found out as 74 wt%. The moisture absorption characteristics of the composite samples were ascertained as per IPC-TM-650 2.6.2.1 method. PTFE/BaWO₄ composite exhibits a dielectric constant of 4.3 and a loss tangent of 0.004 at optimum filler loading.     

Effects of particle size of BaTiO3 powder on the dielectric properties of BaTiO3/polyvinylidene fluoride composites

The effects of particle size of fine BaTiO₃powder on dielectric properties of BaTiO₃/polyvinylidene fluoride (PVDF) composites were investigated. When the frequency of the applied field was less than 100 kHz, the dielectric constant and loss for BaTiO₃/PVDF composites decreased with increasing BaTiO₃particle size. When the frequency was greater than 100 kHz, the opposite results were obtained. The resistivity increased with increasing BaTiO₃particle size, whereas the open areas of hysteresis loops decreased gradually. The degree of poling efficiency for BaTiO₃/PVDF composites increased with increasing BaTiO₃particle size. The BaTiO₃particle size dependence of the dielectric properties of BaTiO₃/PVDF composites is explained by space charge effects at the interface between BaTiO₃and PVDF, and domain configurations (single or multi-domain) of the BaTiO₃powders.     

Dielectric,thermal and mechanical properties of Sr<Subscript>2</Subscript>ZnSi<Subscript>2</Subscript>O<Subscript>7</Subscript> based polymer/ceramic composites

Polymer/Sr₂ZnSi₂O₇ (SZS) ceramic composites suitable for substrate applications have been developed using the polymers polystyrene (PS), high density polyethylene (HDPE) and Di-Glycidyl Ether of Bisphenol A (DGEBA). The dielectric, thermal and mechanical properties of the composites are investigated as a function of various concentrations of the ceramic filler. The obtained values of relative permittivity, dielectric loss tangent, thermal conductivity and coefficient of thermal expansion of the composites are compared with the corresponding theoretical predictions. The relative permittivity of the polymer/ceramic composites increases with filler loading. The dielectric loss tangent also shows the same trend except for DGEBA/SZS composites. The major advantages of the ceramic loading are improvement in thermal conductivity and a decrease in the coefficient of thermal expansion. The tensile strength of the composites decreases with increase in filler content, whereas an improvement is observed in microhardness. The variation of relative permittivity (at 1 MHz) of the composites is also studied as a function of temperature.     

Comparative study of dielectric properties of the PVDF composites filled with spherical and rod-like BaTiO<Subscript>3</Subscript> derived by molten salt synthesis method

In the molten salt environment, the BaTiO₃ spherical nanoparticles (BTNPs) and BaTiO₃ nanorods (BTNRs) have been synthesized, respectively, in which spherical TiO₂ and rod-like BaTi₂O₅ are precursors. The dissolution–precipitation is the main dominated mechanism in the formation of BTNPs, while the dissolution–diffusion is the main mechanism responsible for the formation of BTNRs. The latter is also called as topochemical mechanism, which is associated with the assembly of [TiO₆] octahedron units in the transformation from BaTi₂O₅ to BaTiO₃. By using these two kinds of BT as fillers, polyvinylidene fluoride (PVDF)-based composites, BTNPs/PVDF and BTNRs/PVDF, have been constructed and their dielectric properties have been investigated. It was found that there were three main factors related to filler morphology affecting the dielectric properties of the composites, i.e., intrinsic polarization of filler, the interface polarization and electric field distribution between the filler and the matrix. Though the spontaneous polarization of 600-nm-sized BTNPs is larger, the interfacial area of BTNRs/PVDF composite is larger than that of BTNPs (600 nm)/PVDF composite, which is advantageous to enhance the interface polarization. Moreover, the analysis through Potential-Across model revealed that BTNRs/PVDF composite has stronger electric field intensity distribution across BTNRs filler in comparison with BTNPs/PVDF, which plays the key role in improving the dielectric properties of composites. This work not only presents the BTNRs/PVDF composite with good dielectric performance, the related design and the theory analysis also facilitate the development of more new high dielectric composites based on morphology control of ferroelectric filler.     

Effect of silver incorporation into PVDF-barium titanate composites for EMI shielding applications

Composites of polyvinylidene fluoride (PVDF) with micron and nano sized BaTiO₃ powders were developed for electromagnetic interference (EMI) shielding applications in the X band. PVDF-nano BaTiO₃ composites show better shielding property compared to PVDF-micron sized BaTiO₃ composites. The composite of PVDF with 40 vol% of nano BaTiO₃ showed the best EMI shielding effectiveness and is about 9 dB. The contributions from reflection and absorption to the total EMI shielding effectiveness is same for the PVDF-BaTiO₃ composites. Addition of small amount of silver particles improved the shielding properties of these composites due to the increased conductivity. An EMI shielding effectiveness of about 26 dB is obtained in the measured frequency range for the PVDF-20 vol% nano BaTiO₃-10 vol% Ag composite of thickness 1.2 mm. Novel three phase composite combining the advantages of metal, nano ceramic and polymer is obtained with the potential for effective EMI shielding applications.