Frequency, temperature and In dependent electrical conduction in NiFe2O4 powder

A series of polycrystalline spinel ferrites with the composition NiIn_xFe_2-xO₄ (0 ≤ x ≤ 0.3) were prepared by the solid state reaction to study the effect of In³⁺ ions substitution on their dc electrical resistivity and dielectric properties. The dc resistivity has been investigated as a function of temperature and composition. The indium ion increases the dc resistivity and activation energy of the system. A study of the dielectric properties of these mixed ferrites, as a function of composition, frequency and temperature, has been undertaken. The dielectric constant (ε′), dielectric loss (ε″) and dielectric loss tangent (tanδ) all decreases with frequency as well as with the composition. The dielectric constant (ε′) and dielectric loss tangent (tanδ) were increases with increasing temperature. AC conductivity increases with increase in applied frequency. The dielectric behavior of the present samples is attributed to the Maxwell-Wagner type interfacial polarization. The conduction mechanism in these ferrites is due to electron hopping between Fe²⁺ and Fe³⁺ ions on adjacent octahedral sites.     

Enhancing giant dielectric properties of Ta5+-doped Na1/2Y1/2Cu3Ti4O12 ceramics by engineering grain and grain boundary

Various strategies to improve the dielectric properties of ACu₃Ti₄O₁₂ (A = Sr, Ca, Ba, Cd, and Na_1/2Bi_1/2) ceramics have widely been investigated. However, the reduction in the loss tangent (tanδ) is usually accompanied by the decreased dielectric permittivity (ε′), or vice versa. Herein, we report a route to considerably increase ε′ with a simultaneous reduction in tanδ in Ta⁵⁺–doped Na_1/2Y_1/2Cu₃Ti₄O₁₂ (NYCTO) ceramics. Dense microstructures with segregation of Cu– and Ta–rich phases along the grain boundaries (GBs) and slightly increased mean grain size were observed. The samples prepared via solid-state reaction displayed an increase in ε′ by more than a factor of 3, whereas tanδ was significantly reduced by an order of magnitude. The GB–conduction activation energy and resistance raised due to the segregation of Cu/Ta–rich phases along the GBs, resulting in a decreased tanδ. Concurrently, the grain–conduction activation energy and grain resistance of the NYCTO ceramics were reduced by Ta⁵⁺ doping ions owing to the increased Cu⁺/Cu²⁺, Cu³⁺/Cu²⁺, and Ti³⁺/Ti⁴⁺ ratios, resulting in enhanced interfacial polarization and ε′. The effects of Ta⁵⁺ dopant on the giant dielectric response and electrical properties of the grain and GBs were described based on the Maxwell–Wagner polarization at the insulating GB interface, following the internal barrier layer capacitor model.     

Surface barrier layer effect in (In + Nb) co‐doped TiO2 ceramics: An alternative route to design low dielectric loss

Giant dielectric permittivity (ε′) with low loss tangent (tanδ) was reported in (In + Nb) co‐doped TiO₂ ceramics. Either of electron‐pinned defect‐dipole or internal barrier layer capacitor model was proposed to be the origin of this high dielectric performance. Here, we proposed an effectively alternative route for designing low‐tanδ in co‐doped TiO₂ ceramics by creating a resistive outer surface layer. A pure rutile‐TiO₂ phase with a dense microstructure and homogeneous dispersion of dopants was achieved in (In + Nb) co‐doped TiO₂ ceramics prepared by a simple sol‐gel method. Two giant dielectric responses were observed in low‐ and high‐frequency ranges, corresponding to extremely high ε′≈10⁶‐10⁷ and large ε′≈10⁴‐10⁵, respectively. After annealing in air, a low‐frequency dielectric response disappeared and could be restored by removing the outer surface of the annealed sample, indicating the dominant electrode effect in the initial sample. Annealing can cause improved dielectric properties with a temperature‐ and frequency‐independent ε′ value of ≈1.9 × 10⁴ and cause a decrease in tanδ from 0.1 to 0.035. High dielectric performance in (In_0.5Nb_0.5)_xTi_1?xO₂ ceramics can be achieved by eliminating the electrode effect and forming a resistive outer surface layer.     

Fourier transform infrared spectroscopic and AC electrical conductivity studies of chitin and its derivatives

The vibrational modes and the purity index of chitin and its derivatives as biopolymers are studied by Fourier transform infrared spectroscopy in the wavenumber range from 4000 to 400 cm^?1. The absorption bands of chitin and its derivatives are assigned. New bands appeared at 1419, 1209, 915, and 800 cm^?1 for chitin derivatives due to the change of vibrational modes. The purity indexes are calculated from the ratio of the absorption band of C = O at 1662 cm^?1 and OH at 3443 cm^?1. Generally, the purity indexes of chitin derivatives are higher than that of chitin, which is due to the decrease of OH. The dielectric properties such as the real part of the dielectric constant (ε′) and loss tangent tan (δ) are measured as a function of temperature at different frequencies ranging from 200 to 2000 kHz. The increase of (ε′) and tan (δ) with increasing temperature is discussed on the basis of increasing polarizability and the decrease with increasing frequency can be attributed to the dielectric dispersion. AC electrical conductivities as a function of the reciprocal of the absolute temperature are also discussed. The mechanism of the charge carrier is discussed as a tunneling model in the temperature range from 300 to 360 K. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 936–943, 2005     

Structural,dielectric and ferromagnetic behavior of (Zn,Co) co-doped SnO2 nanoparticles

Nanoparticles of basic composition Sn_0.94Zn_0.05Co_0.01O₂, Sn_0.92Zn_0.05Co_0.03O₂ and Sn_0.90Zn_0.05Co_0.05O₂ were synthesized by chemical precipitation method. The incorporation of Co and Zn in SnO₂ lattice introduced significant changes in the physical properties of all the three nanocrystals. The average particle size estimated from TEM data decreased from 15.71 to 6.41  nm with enhancement in concentration of oxygen vacancies as Co content is increased from 1 to 5 wt%. Increasing Co content enhanced the Sn:O atomic ratio as a result concentration of oxygen vacancies increased. The dielectric study revealed strong doping dependence. The dielectric parameters (ε′, tanδ and σ_ac) increased with increasing Co content and attained maximum values for 5% (Zn, Co) co-doped SnO₂ nanoparticles. The dielectric loss (ε′′) exhibited dispersion behavior and the Debye’s relaxation peaks observed in dielectric loss factor (tanδ), whose intensities increased with increasing Co content. The variation of dielectric properties and ac conductivity revealed that the dispersion is due to Maxwell-Wagner interfacial polarization and hopping of charge carriers between Sn⁺²/Sn⁺³ and Co⁺²/Co⁺³. The large dielectric constant of all samples made them interesting materials for device application. Magnetization measurements (M (H) loops) revealed enhancement in saturation magnetization with doping which is due to the formation of large amount of induced defects and oxygen vacancies in the samples. The present study clearly reveals doping dependent properties and the oxygen vacancies induced ferromagnetism in Zn, Co co-doped SnO₂ nanoparticles having applications in ultra-high dielectric materials, high frequency devices and spintronics.     

Cd-substituted Mg composites with dual-equivalent permeability and permittivity for high-frequency miniaturization antennas

Spinel Mg ferrites Mg_1-xCd_xCo_0.05Fe_1.95O₄ (x=0.0, 0.2, 0.3 and 0.4) as potential agents for the miniaturization of high frequency antennas are presented. All the synthesized compositions were experimentally revealed to possess pure spinel phase. Dual-equivalent permeability and permittivity (μ'≈26, ε'≈25, x=0.3 and μ'≈29, ε'≈28, x=0.4) from 5 to 100 MHz can be achieved by introducing Cd²⁺ ions, yielding large miniaturization factors of up to 25 and 28. To figure out the effects of Cd²⁺ ions substitution on magnetic and dielectric properties, the change in microstructure is mainly investigated. Meanwhile, enhanced magnetic properties including upward saturation magnetization (Ms) (approximately 47.60 emu/g) and reduced coercivity (approximately 54.22 Oe) are obtained due to increased grain size and denser microstructure arrangements reflected from scanning electron microscopy images. With low magnitude order of magnetic and dielectric losses factors (tanδ_ε reaches 10^-4, tanδ_μ reaches 10^-2), the composites can potentially exhibit high operating efficiencies at high frequencies.     

Effects of annealing temperature on structure and electrical properties of sol–gel derived 0.65PMN-0.35PT thin film

0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ (0.65PMN-0.35PT) thin films were deposited on Pt/Ti/SiO₂/Si substrates annealed from 550 to 700 °C using sol-gel process. The effects of annealing temperature on microstructure, insulating, ferroelectric and dielectric properties were characterized. The result reveals that 0.65PMN-0.35PT thin films possess a polycrystalline structure, matching well with the perovskite phase despite the existence of a slight pyrochlore phase. The film samples annealed at all temperatures exhibit relatively dense surfaces without any large voids and the grain size increases generally with the increase of the annealing temperature. Meanwhile, pyrochlore phase is considerably generated because of the deformation of perovskite phase caused by volatilization of Pb at an excessive high-temperature. The film annealed at 650 °C exhibits superior ferroelectricity with a remanent polarization (P_r) value of 13.31 μC/cm², dielectric constant (ε_r) of 1692 and relatively low dielectric loss (tanδ) of 0.122 at 10⁴ Hz due to the relatively homogeneous large grain size of 130 nm and low leakage current of approximately 10^-6 A/cm².     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.     

Influence of the stoichiometry,microstructure, and metallization method on the dielectric properties of 0.94 Na0.5Bi0.5TiO3-0.06 BaTiO3

The morphotropic composition of the lead-free solid solution between Na_0.5Bi_0.5TiO₃ and BaTiO₃ (0.94 Na_0.5Bi_0.5TiO₃-0.06 BaTiO₃ or NBT-6BT) is of particular interest for the next generation of high-temperature capacitors but remains plagued by the diversity of dielectric properties reported in the literature. In order to explain the apparent inconsistencies among the reported dielectric properties of NBT-6BT, we examine the influence of stoichiometry, phase separation, and metallization method. We show that the nominal stoichiometry has a crucial effect, since increasing the nominal Na/Bi ratio increases conductivity and dielectric losses (tan δ). It also increases the real part of the permittivity (ε’) and the frequency dispersion of both ε’ and tan δ, thereby altering the shape of the evolution with temperature of the dielectric properties. Moreover it increases the depolarization temperature (T_d) and decreases the temperature of maximum permittivity (T_m). Phase separation also occurs during the synthesis of NBT-6BT as Na evaporation leads to the formation of secondary Ba-containing phases. We report that these phases can have a positive impact on the dielectric properties: a moderate volume fraction (2.5 to 3.0%) and average grain surface (0.9 to 3.0 µm²) of these secondary Ba-containing phases increase the relative permittivity, decrease the dielectric losses, and increase the insulation resistance. We also show that the metallization method impacts the dielectric properties and therefore may contribute to the differences between various reports. The dielectric properties of NBT-6BT samples are measured during successive heating/cooling cycles and reveal that the permittivity value is lower during the first heating when silver paste, even cured, is used. These three components contribute to explaining the diversity of the reported dielectric properties of NBT-6BT.     

Viscoelastic,thermo-mechanical and environmental properties of composites based on polypropylene/poly(lactic acid) blend and copper modified nanoclay

Poly(lactic acid) (PLA)/polypropylene (PP) blends composites were prepared by incorporating 3 wt.% of copper modified montmorillonite (MMT-Cu²⁺), obtained using cation exchange in a CuSO₄ solution, and 10 wt.% of polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer then varying the PLA content until 50 wt.%. These materials were subjected to several investigations such as X-rays diffraction, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile and environmental tests. The DMTA analysis showed that the glassy PLA high stiffness and the PP crystalline phase compensate the decrease in the storage modulus occurring during the PP and PLA glass transitions, respectively. The variations of tan δ revealed no changes on the PP and PLA phases glass transitions temperatures which indicate the immiscibility of the two polymers, as supported by DSC analysis. Blends composites SEM micrographs stated the immiscibility of the system resulting in the poor adhesion of the PLA droplets to the PP matrix. Also, the blends composites exhibited intermediate tensile properties between those of PP and PLA. The incorporation of MMT-Cu²⁺ to the (50/50) PP/PLA blend accentuated its aptitude to water absorption and ensured an efficient antimicrobial activity over a satisfactorily long period of around six months.     

Effects of hetero-armed star-shaped PCL-PLA polymers with POSS core on thermal,mechanical, and morphological properties of PLA

In this study, AB type-heteroarm star-shaped poly(ε-caprolactone)-poly(lactic acid) (PCL-PLA) polymers with polyhedral oligomeric silsesquioxane (POSS) core ((PCL)₄-POSS-(PLA)₄, coded as SPLA) were synthesized successfully by using ring opening polymerization and click chemistry techniques together. The synthesized polymers were compounded with commercial PLA at different blending ratios (PLA/SPLA = 100/0, 95/5, 90/10, and 80/20% wt). The effects of heteroarm SPLA polymers having different arm lengths (n = 10, 20, 30, and 50) on morphological, mechanical, and thermal behaviors of PLA were investigated. It is determined that SPLA polymers with four PLA and four PCL arms on its structure enhanced mechanical properties of PLA. The tensile modulus decreased, and lowest modulus values were observed with blends prepared at 80/20 ratio. Elongation at break values increased in all blends, maximum increment was observed with 1,4-phenylene diisocyanate (PDI) containing SPLA20 blends prepared at 90/10 ratio. This result showed that SPLA20 had optimum chain length for chain extension reactions of between PLA chains. Besides, a trade compatibilizer PDI was utilized to enhance the intercompatibility of binary polymer blends.     

Frequency and voltage dependence of dielectric properties,complex electric modulus,and electrical conductivity in Au/7% graphene doped‐PVA/n‐Si (MPS) structures

In order to increase the capacitance of Au/n‐Si (MS) structure, 7% graphene doped PVA was coated on n‐Si as an interfacial layer. The measured data of capacitance (C) and conductance (G/ω) of Au/7% graphene doped‐PVA/n‐Si (MPS) structure was utilized for the calculation of real and imaginary parts of complex permittivity (ε^* = ε′ − jε″), loss tangent (tanδ), complex electric modulus (M^* = M′ + jM″), and electrical conductivity (σ). The admittance measurements (C and G/ω) were carried out in the frequency range of 0.5 kHz to 1 MHz at room temperature. Frequency dependence of the dielectric constant (ε′), dielectric loss (ε″) and tanδ shows a dispersive behavior at low frequencies. This behavior was explained by Maxwell–Wagner relaxation. Due to the dipolar and the interfacial polarizations, as well as the surface states (N_ss) and the interfacial PVA layer, the parameters exhibited a strong dependence on frequency and applied bias voltage. The σ versus log(f) plot exhibited both low and high frequency dispersion phenomena such that at low frequencies σ value corresponding to the dc conductivity (σ_dc), but at high frequencies it corresponds to the ac conductivity (σ_ac). M′ and M″, both, have low values in the low frequency region. However, an increase is observed with the increasing frequency due to the short‐range mobility of charge carriers. As a result, the change in dielectric parameters and electric modulus with frequency is the result of relaxation phenomena and surface states. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43827.     

原位反应增容制备可生物降解PLA/PCL复合材料

基于原位反应增容原理制备了一种可生物降解的聚乳酸(PLA)/聚己内酯(PCL)共混材料。探究了PLA/PCL不同配比及相容剂乙烯-丙烯酸丁酯-甲基丙烯酸缩水甘油酯(EBA-GMA)(8份)对增韧效果的影响,目的是研究设计一种增韧效果最佳的PLA/PCL/EBA-GMA可降解材料。并采用平板流变仪、傅里叶红外光谱仪(FTIR)、扫描电子显微镜(SEM)及差示扫描量热法(DSC)对其反应机理、微观形貌及热性能进行了表征。结果表明,在不加相容剂时,PLA/PCL(80/20)能取得最好的增韧效果;加入8份相容剂后,PLA/PCL(85/15)的缺口冲击强度达75.4 kJ/m^2,增韧效果最好。     

Biodegradable polyester blends for biomedical application

A new family of bioabsorbable materials suitable for biomedical applications was designed and prepared by means of blending of some available polyesters to develop new biodegradable materials tailored for different requirements. Multiphase polymer blends containing poly(d, l-lactide) (PLA), poly(ε-caprolactone) (PCL), poly(d, l)-lactide-co-poly(ethylene glycol) (PELA), poly(ε-caprolactone) -co-poly(ethylene glycol) (PECL), and poly(ß-hydroxybutyrate) (PHB), PLA/PCL, PELA/PECL, PHB/PLA, PHB/PELA, PHB/PCL, and PHB/PECL blends were respectively investigated. It was found that PLA/PCL, PHB, and PHB/PLA and PHB/PCL blends were seemingly immiscible, with their morphology and hydrolytic behavior were determined by the composition of the blends. On the other hand, the miscibility of PELA/PECL, PHB/PELA, and PHB/PECL blends was improved by using PELA and/or PECL block copolymers that contained poly(ethylene glycol) (PEG) as compatibilizer. The blends showed to a certain extent miscibility, fine phase morphology, and fast hydrolysis. © 1995 John Wiley & Sons, Inc.     

Effect of block copolymer containing ionic liquid moiety on interfacial polarization in PLA/PCL blends

Compared with poly(?‐caprolactone)‐b‐poly(ethylene glycol) block copolymer (BC), a systematic study of the effect of the concentration of the compatibilizer, poly(?‐caprolactone)‐b‐poly(ethylene glycol) BC containing ionic liquid moiety (BCIL), on the interfacial properties of a phase separating blend of poly(l ‐lactic acid)/poly(?‐caprolactone) (PLA/PCL) was performed. BCIL copolymer as a compatibilizer for immiscible PLA/PCL blend can reinforce the interactions between the two polymeric phases by the IL electrostatic interaction at interphase, and the particle size of PCL decreases because of interfacial reinforced‐compatibilization of IL moiety. Ion mobility of IL moiety at interphase and PCL phase for PLA/PCL/BCIL blend can induce interfacial blocking of charge carriers, and IL moiety segregating mainly at the interface can decrease the relaxation rate and increase the dielectric strength of interfacial polarization. Our results provide a methodology to characterize and tune the morphology and blocking of charge carriers with the aim of tailoring the dielectric interfacial properties of blends. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46161.     

Flexible dielectric ZnO-doped reduced graphene oxide bionanocomposites from solution blending for potential application in bio-related devices

Biocompatible materials with high dielectric constant and low dielectric loss have applications in bio-related electronic devices. Development of flexible materials with those properties is still a challenge. In this work, electrospun membranes and films are prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) solutions, incorporated with a reduced graphene oxide-zinc oxide composite (rGO-ZnO). Blending CS with flexible PVA favors electrospinnability and mechanical properties. ZnO contributes to hinder agglomeration of conductive rGO sheets. The structural, mechanical, dielectric and electrical properties of the hybrid materials are investigated. Infrared spectroscopy reveals interaction between the filler and the polymeric components. For mats and films, the increase in rGO-ZnO content leads to lower crystallinity. The Young's modulus and stress at break values increase with increasing rGO-ZnO content. High dielectric constants (ε' = 132 to ε' = 166, at 10³ Hz), associated with low dielectric loss factor (tan δ = 0.02), are determined for the PVA/CS/rGO-ZnO films.     

Study on the Crystallization,Miscibility, Morphology,Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA₇₀PCL₃₀ blend. This result reveals that the PLA₇₀PCL₃₀ blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the T_g. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA₇₀PCL₃₀ blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.     

Effect of interface affinity on the performance of a composite of microcrystalline cellulose and polypropylene/polylactide blends

The effects of compatibilizer and fillers on the mechanical properties and dispersion state of droplets of polypropylene (PP)/polylactide (PLA) blends were investigated. Two blended composite systems, i.e. PP‐rich (80/20) containing microcrystalline cellulose (MCC) modified with silane (m‐MCC) and PLA‐rich (20/80) containing MCC were prepared by melt compounding using a twin‐screw extruder. The structural differences between MCC and m‐MCC were confirmed using Fourier transform infrared spectra. Universal testing machine results revealed that the tensile strength and Young's modulus increased with the addition of compatibilizer and filler, respectively. These results were supported by the reduction of domain size observed by scanning electron microscopy. Differential scanning calorimetric analysis showed a change of the melting and crystallization behavior of blends according to the presence of compatibilizer or filler. An increase of the dynamic storage modulus and a decrease in tan δ with addition of compatibilizer indicated that the interfacial adhesion between PP and PLA improved. © 2019 Society of Chemical Industry     

Viscoelastic,thermal and environmental characteristics of poly(lactic acid), linear low-density polyethylene and low-density polyethylene ternary blends and composites

Poly(lactic acid) (PLA)/(linear low-density polyethylene (LLDPE)–low-density polyethylene (LDPE)) PLA/(LLDPE-LDPE) ternary blends were prepared and characterized as function of the PLA content. (50/50) PLA/(LLDPE–LDPE) blend was also compatibilized using maleic anhydride grafted low-density polyethylene (PE-g-MA) incorporated with a concentration of 5 wt.%. PLA/(LLDPE–LDPE) blend composites have been prepared by dispersing 5 wt.% of an organophilic montmorillonite (Org-MMT), added according to two different mixing methods. These materials were subjected to several investigations such as X-rays diffraction (XRD), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry, and environmental tests. In the PLA glassy region, DMTA results showed that the storage modulus of PLA/(LLDPE–LDPE) blends decreases upon decreasing the PLA content. When PE-g-MA and Org-MMT were added, PLA exhibited a noticeable increase in the storage modulus across the glass transition region due the interface reinforcement and the enhancement of the blends stiffness. The decrease in the magnitude of the PLA tan δ peak was attributed to the decrease in the molecular mobility that could result from the increase in the interfacial resistance. XRD analysis showed that the method of dispersion of the nanoclay controls the final structural properties of the composites. (50/50) PLA/(LLDPE-LDPE) blend and composites revealed a satisfactory aptitude to biodegradation.     

Influence of solid loading on densification behavior,micromorphology and dielectric properties of Ba0.67Sr0.33TiO3 ceramics fabricated by a novel DCC-HVCI method

Ba_0.67Sr_0.33TiO₃ (BST) ceramics with highly improved dielectric performance were fabricated by a novel direct coagulation casting via high valence counter ions (DCC-HVCI) method. The influence of solid loading on densification behavior, micromorphology, and dielectric performance of the samples was investigated. With the increase of solid loading from 40 to 50 vol%, the maximum densification rate of BST ceramics increased from 0.090 to 0.122 s⁻¹, and the densification temperature decreased from 1424 to 1343 °C, which indicated that high solid loading could promote the densification behavior of samples during sintering. BST ceramics fabricated by the DCC-HVCI method showed uniform grain size and microstructure, which was beneficial for the dielectric properties of BST ceramics. Samples obtained from 45 vol% suspensions possessed the lowest dielectric permittivity (ε_r ≈ 2801), and the dielectric loss (tanδ≈0.0262) was about 1/10 of that of dry-pressed samples (tanδ≈0.301), which could be attributed to the composition homogenization.