Barium Titanate Composites Research Articles

Reinforced properties of ethylene–propylene–diene monomer composites by vinyltrimethoxysiloxane functionalised barium titanate

In this study, non-conductive ethylene–propylene–diene monomer (EPDM)/barium titanate (BaTiO3) composites with high dielectric constant and low dielectric loss are prepared. Fourier transform infrared (FT-IR) spectra show the chemical adherence of vinyltrimethoxysiloxane oligomer (SG-Si6490) to the surface of BaTiO3 particles. Functionalised BaTiO3 particles have better compatibility with EPDM matrix and promote the cure properties of EPDM composites. It is found that when the content of BaTiO3 increases to 40 vol.-%, the resistivity, rheological, dielectric and mechanical properties of EPDM/BaTiO3 composites change drastically. The dielectric constant of EPDM with 50 vol.-% BaTiO3 at 10 MHz is 15, which is 7.5 times higher than that of EPDM control. Meanwhile, the volume resistivity results show EPDM with 50 vol.-% BaTiO3 is still non-conductive. As for mechanical properties, the tensile and tear strength of EPDM control increase from 1.45 MPa and 8.73 kN m−1 to 10.02 MPa (about seven times higher) and 24.65 kN m−1 (about three times higher), respectively.

Impedance spectroscopy and mechanical response of porous nanophase hydroxyapatite–barium titanate composite

The present study aims to develop the porous nanophase hydroxyapatite (HA)–barium titanate (BT) composite with reasonable mechanical and electrical properties as an electrically-active prosthetic orthopedic implant alternate. The porous samples (densification ~40–70%) with varying amounts of BT (0, 25, 35 and 100vol.%) in HA were synthesized using optimal spark plasma sintering conditions, which revealed the thermochemical stability between both the phases. The reasonably good combination of functional properties such as compressive [(236.00±44.90)MPa] and flexural [(56.18±5.82) MPa] strengths, AC conductivity [7.62×10−9(ohm-cm)−1 at 10kHz] and relative permittivity [15.20 at 10kHz] have been achieved with nanostructured HA-25vol.% BT composite as far as significant sample porosity (~30%) is concerned. Detailed impedance spectroscopic analysis was performed to reveal the electrical microstructure of developed porous samples. The resistance and capacitance values (at 500°C) of grain (RG, CG) and grain boundary (RGB, CGB) for the porous HA-25vol.% BT composite are (1.3×107 ohm, 3.1×10−11F) and (1.6×107 ohm, 5.9×10−10F), respectively. Almost similar value of activation energy (~1–1.5eV) for grain and grain boundary has been observed for all the samples. The mechanism of conduction is found to be same for porous monolithic HA as well as composite samples. Relaxation spectroscopic analyses suggest that both the localized as well as long range charge carrier translocations are responsible for conduction in these samples. The degree of polarization of porous samples has been assessed by measuring thermally stimulated depolarization current of the poled samples. The depolarization current is observed to depend on the heating rate. The maximum current density, measured for HA-25vol.% BT sample at a heating rate of 1°C/min is 2.7nA/cm2. Formation of oxygen vacancies due to the reduced atmosphere sintering contribute to the space charge polarization, which is obtained as the dominant polarization mechanism in the developed porous samples. Overall, such integrated functional responses do establish spark plasma sintered porous HA–BaTiO3 nanocomposite as potential alternative for electroactive prosthetic orthopedic implants.

Aging behavior of the silicone dielectric elastomers in a simulated marine environment

A series of silicone–barium titanate composites, designed as dielectric elastomer films to be used as active elements in wave energy conversion devices, were immersed in artificial sea water in pseudo-dynamic conditions to asses their aging behavior.

Dielectric investigation of the composites based on thiourea

The composites of thiourea and lithium niobate as well as lead titanate and barium titanate (thiourea fraction was 0.90 for all cases) have been studied by dielectric spectroscopy close to structural phase transitions in thiourea. It was found that the hysteresis increased and the temperature of ferroelectric phase transition from phase I to phase II decreased for all compositions investigated in comparison with the same properties of polycrystalline thiourea. The largest lowering of the phase transition temperature was observed for the thiourea and barium titanate composite. The results are analyzed within the framework of Landau–Ginzburg theory.

Preparation and properties of BaTiO3 filled butyl rubber composites for flexible electronic circuit applications

Butyl rubber–micron barium titanate (BR/BT) and butyl rubber–nano barium titanate (BR/nBT) composites were prepared by sigma mixing followed by hot pressing. The tensile tests show that both the composites were mechanically flexible. The microwave dielectric properties of both BR/BT and BR/nBT composites were investigated as a function of ceramic loading and were found to be improved with filler content. The butyl rubber has a relative permittivity (er) of 2.4 and loss tangent (tan δ) of 0.0017 at 5 GHz. At a filler loading of 0.24 volume fraction (vf) of micron sized barium titanate (BaTiO3) powder loading, the composite attained a er of 7 and tan δ of 0.014 and for the same filler content of nano BaTiO3 the composite have er of 8.9 and tan δ of 0.019 at 5 GHz. The thermal and mechanical properties of both the composites were investigated. The experimental values of er of both BR/BT and BR/nBT composites for different volume fractions were compared with theoretical models.

Absence of systemic toxicity in mouse model towards BaTiO3 nanoparticulate based eluate treatment.

One of the existing issues in implant failure of orthopedic biomaterials is the toxicity induced by the fine particles released during long term use in vivo, leading to acute inflammatory response. In developing a new class of piezobiocomposite to mimic the integrated electrical and mechanical properties of bone, bone-mimicking physical properties as well as in vitro cytocompatibility properties have been achieved with spark plasma sintered hydroxyapatite (HA)-barium titanate (BaTiO3) composites. However, the presence of BaTiO3 remains a concern towards the potential toxicity effect. To address this issue, present work reports the first result to conclusively confirm the non-toxic effect of HA-BaTiO3 piezobiocomposite nanoparticulates, in vivo. Twenty BALB/c mice were intra-articularly injected at their right knee joints with different concentrations of HA-BaTiO3 composite of up to 25mg/ml. The histopathological examination confirmed the absence of any trace of injected particles or any sign of inflammatory reaction in the vital organs, such as heart, spleen, kidney and liver at 7days post-exposure period. Rather, the injected nanoparticulates were found to be agglomerated in the vicinity of the knee joint, surrounded by macrophages. Importantly, the absence of any systemic toxicity response in any of the vital organs in the treated mouse model, other than a mild local response at the site of delivery, was recorded. The serum biochemical analyses using proinflammatory cytokines (TNF-α and IL-1β) also complimented to the non-immunogenic response to injected particulates. Altogether, the absence of any inflammatory/adverse reaction will open up myriad of opportunities for BaTiO3 based piezoelectric implantable devices in biomedical applications.

Zirconia doped barium titanate induced electroactive β polymorph in PVDF-HFP: high energy density and dielectric properties

Zirconium-doped barium titanate (BZT-08, Ba(Ti0.92 Zr0.08)O3) particles were synthesized and PVDF-HFP-based composites were prepared by melt mixing to design materials with tunable dielectric and ferroelectric properties. Composites of PVDF-HFP and barium titanate (BT) particles were also prepared to realize the exceptional properties associated with the BZT-08-like stabilization of two ferroelectric phases, i.e. tetragonal and orthorhombic at room temperature. To facilitate the uniform dispersion and interfacial adhesion with the matrix, the particles were modified with (3-aminopropyl) triethoxysilane. The dependence of the dielectric and ferroelectric properties of the as-prepared composites were systematically investigated in this study with respect to a wide range of frequencies. The composites with BZT-08 exhibited the significantly high dielectric permittivity of ca. 26 (at 100 Hz) and a high energy density (2.7 J cm−3 measured on 100 μm thick film) at room temperature with respect to the control PVDF-HFP and PVDF-HFP/BT composites. Interestingly, the BZT-08 particles facilitated the electroactive β polymorph in the PVDF-HFP and enhanced polarization in the composites, leading to improved ferroelectric properties in the composites.

Polydimethylsiloxane–barium titanate composites: Preparation and evaluation of the morphology, moisture, thermal, mechanical and dielectric behavior

Polydimethylsiloxane-α,ω-diols were used as matrix for barium titanate particles to obtain electroactive elastomeric composites. Filler particles were previously treated with a surfactant to improve the compatibility with and dispersibility in the matrix. The composites, processed as films and crosslinked with methyltriacetoxysilane, were investigated from point of view of the morphology, moisture sorption and thermal properties, as well as mechanical and dielectric behavior. Maximum strain value of 850% at 0.32MPa and dielectric permittivity of 4.41 at 10Hz and 20°C were obtained. Two parameters of interest for potential future application of such materials in electromechanical devices (actuation or harvesting), electromechanical sensitivity and harvesting energy capacity, were estimated and discussed in correlation with the molecular mass of the polymeric matrix and the content of the active filler.

Features of structure and properties of biopolymer composites with inorganic nanoparticles

The morphology, atomic structure, and strength characteristics of composites of barium titanate and silicon dioxide nanoparticles with biopolymers (collagen, lignin, starch) were investigated. Both changes in the inner structures and oriented ordering of morphology were found in the composites of barium titanate with collagen. Formations of quasi-parallel rows from silicon dioxide nanoparticles were found in the collagen composites with silicon dioxide. Thermal resistance of the collagen increased significantly in the process. Formation of a three-dimensional periodic structure from spherical nanoparticles was found in the composites of silicon dioxide with lignin. Interaction mechanisms of nanoparticles and biopolymers causing formation of the observed structures are discussed.

Enhanced electro-optical properties of a nematic liquid crystals in presence of BaTiO3 nanoparticles

Composites of nematic liquid crystals (NLCs) and ferroelectric barium titanate (BaTiO3) nanoparticles (NPs) have been prepared. The alignments of NPs in the host medium have been demonstrated. Effect of NPs doping on various display parameters of NLCs, namely, threshold voltage, dielectric anisotropy and splay elastic constant has been studied using electro-optical and dielectric studies. The nematic ordering of host supports alignment of NPs parallel to the director which consequently improves electro-optical parameters in the composite system. The dielectric and electro-optic properties of LC–NPs composites have been discussed in frame of conventional theories of NLCs.

Piezoelectric and pyroelectric properties of zirconium substituted barium titanate ferroelectric ceramics

In present study, Piezoelectric and pyroelectric properties of zirconium substituted barium titanate compositions (BaZrxTi1−xO3) (x = 0–0.1) have been investigated, as Zr+4 possesses more chemical stability than Ti+4 ions. The grain size increases from 0.55 μm for x = 0.0–3.2 μm for x = 0.025 and 6.15 μm for x = 0.05. With further Zr substitution, grain size decreases to 0.5 μm for x = 0.075 and 0.33 μm for x = 0.1. With increase in sintering temperature from 1,200 to 1,300 °C, the piezoelectric coefficient of BaZr0.025Ti0.975O3 increases from 40.1 to 189.2 pC/N and this is correlated to the type of domain structures. Zr content influences grain size and domain structures leading to an appreciable change in dielectric constant as well as piezoelectric and pyroelectric properties. The value of pyroelectric coefficients increases from 72.23 μC/m2 °C for x = 0.0–5,984.095 μC/m2 °C for x = 0.025 and decreases to 2,719.68 μC/m2 °C for x = 0.05 and 5.96 μC/m2 °C for x = 0.1. The value of figure of merit of x = 0.025 i.e. 1.22 proves its better suitability for infrared detectors.

Silicone–barium titanate composites with increased electromechanical sensitivity. The effects of the filler morphology

Dielectric elastomers were prepared on the basis of high molecular weight polydimethylsiloxane-α,ω-diol filled with barium titanate particles having well-defined size and morphology.

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.

Dependence of magnetoelectric properties on the magnetostrictive content in 0–3 composites

The magnetoelectric response in composites of barium titanate (BTO) and cobalt ferrite (CFO) has been determined by measuring the magnetoelectric susceptibility coefficient. This was done by two different methods: magnetocapacitance measurements and magnetoelectric voltage measurement using a lock-in technique. These composites were prepared by the sol–gel method. Four different compositions with different molar ratios of the magnetostrictive phase (CFO) embedded in a piezoelectric matrix of BTO were studied to investigate the effect of the magnetostrictive content and the number density of interfaces on the magnetoelectric response. It was found from both techniques that the magnetoelectric coupling effect increases with the increase of applied field and it had a non-linear dependence on the percentage of magnetostrictive content in the composites.

Microwave Dielectric Characteristics of Butyl Rubber- Barium Titanate Composites

Butyl rubber-micron barium titanate (BR/BT) and butyl rubber-nano barium titanate (BR/nBT) composites were prepared by sigma mixing followed by hot pressing. The tensile tests show that both the composites were mechanically flexible. The microwave dielectric properties of both BR/BT and BR/nBT composites were investigated as a function of ceramic loading and were found to be improved with filler content. The butyl rubber has relative permittivity (εr) of 2.4 and loss tangent (tan δ) of 0.0017 at 5 GHz. At a filler loading of 0.24 volume fraction (vf) of micron sized barium titanate (BaTiO3) powder loading, the composite attained a εr of 7 and tan δ of 0.014 and for the same filler content of nano BaTiO3 the composite have εr of 8.9 and tan δ of 0.019 at 5 GHz. The thermal stability of the relative permittivity of both the composites was investigated. The experimental values of εr of both BR/BT and BR/nBT composites were compared with theoretical models.

Dielectric response, functionality and energy storage in epoxy nanocomposites: Barium titanate vs exfoliated graphite nanoplatelets

Barium titanate/epoxy and exfoliated graphite nanoplatelets/epoxy nanocomposites were prepared and studied varying the filler content. Morphological characteristics were examined via scanning electron microscopy, while structural changes occurring in barium titanate as a function of temperature were investigated by means of X-ray diffraction. Broadband dielectric spectroscopy was employed for determining the dielectric response of the prepared systems. Based on the conducted analysis it was found that three relaxation processes are present in the spectra of the examined materials. From the slower to the faster one, these are interfacial polarization, glass to rubber transition of the polymer matrix, and rearrangement of polar side groups of the polymer chain. Systems' functionality and energy storing efficiency were assessed in terms of dielectric reinforcing function. Finally, the energy density of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites.

Effects of the chemical composition of the magnetostrictive phase on the dielectric and magnetoelectric properties of cobalt ferrite–barium titanate composites

Magnetostrictive–piezoelectric composites of CoFe 2O 4–BaTiO 3 and CoMn 0.2Fe 1.8O 4–BaTiO 3 were obtained with standard solid-state ceramic processing. X-ray diffraction (XRD) analysis revealed the presence of the spinel and perovskite phase without the appearance of the residual phase. The influence of the phase content on the dielectric constant, loss tangent, magnetization, magnetostriction and magnetoelectric signal was studied, and the results were correlated with the microstructure and the amount of ferrite. The magnetoelectric response of the composite indicated that the substitution of iron ions for manganese ions decreased the dielectric loss and improved the magnetoelectric signal of the composite samples.

Dielectric and ferroelectric properties of 1-3 barium titanate–Portland cement composites

In the current work, the dielectric and ferroelectric properties of 1-3 barium titanate (BT)–Portland cement (PC) composites have been studied as potential lead-free piezoelectric-cement-based composites. The 1-3 BT–PC composites were fabricated by a dice-and-fill technique with BT:PC ratios of 50:50, 60:40 and 70:30 by volume. The results indicate that the dielectric constant ( ε r ) of the composite materials increases as the barium titanate volume fraction increases; this follows the parallel model. The room temperature ε r at 1 kHz of 70% barium titanate composite was found to have values higher than 750. The loss tangent (tan δ) results were found to decrease with increasing barium titanate volume fraction. On the other hand, the ferroelectric hysteresis loops of composite materials indicate that the “instantaneous” remnant polarization ( P ir ) increases as the barium titanate volume fraction increases. The P ir at 15 kV/cm (90 Hz) of 70% barium titanate composite was found to have a value of ≈3 μC/cm 2.

Dielectric, ferroelectric and piezoelectric properties of 0-3 barium titanate–Portland cement composites

In this work, barium titanate (BT) and cement composites of 0-3 connectivity were produced with BT concentrations of 30%, 50% and 70% by volume using the mixing and pressing method. The dielectric constant (er) and the dielectric loss (tan δ) at room temperature and at various frequencies (0.1–20 kHz) of the ferroelectric BT-Portland cement composites with different BT concentrations were investigated. The results show that the dielectric constant of BT-PC composites was found to increase as BT concentration increases, and that the highest value for er—of 436—was obtained for a BT concentration of 70%. In addition, the dielectric loss tangent decreased with increasing BT concentration. Moreover, several mathematical models were used; the experimental values of the dielectric constants are closest to those calculated from the cube model. The 0-3 cement-based piezoelectric composites show typical ferroelectric hysteresis loops at room temperature. The instantaneous remnant polarization (Pir), at an applied external electrical field (E0) of 20 kV/cm (90 Hz) of 70% barium titanate composite, was found to have a value ≈3.42 μC/cm2. Furthermore, the piezoelectric coefficient (d33) was also found to increase as BT concentration increases, as expected. The highest value for d33 was 16 pC/N for 70% BT composite.

Dielectric Properties and Conductivity of Iron Oxide-Barium Titanate Composites

Sintered composites of iron oxide plus barium titanate in form of core-shell structures are investigated by impedance spectroscopy. The measurements were performed in the frequency and temperature ranges 20 Hz to 1 MHz and 150 K to 510 K, respectively. The composites exhibit strong low-frequency dispersion of electrical modulus and dielectric permittivity which is caused by different mechanisms of electron transfer at low and high temperatures. A hopping transport process with activation energy of 0.22 eV for exchange between Fe2+ and Fe3+ was tentatively assigned to reign below room temperature. It gradually changes to a conducting mechanism with activation energy of 0.45 eV above 345 K.