Ferroelectric hysteresis behavior and dielectric properties of 1–3 lead zirconate titanate–cement composites

Lead zirconate titanate (PZT) ceramic was mixed with Portland cement (PC) to form 1–3 connectivity PZT–PC composite using a dice-and-fill technique. Ferroelectric hysteresis behavior and dielectric properties of these composites were investigated using PZT volume content of 60%, 70% and 80%. The results showed that the dielectric constant of the composite materials increased with PZT content and the dielectric constant (?_r) value is 781 for 80% PZT composite at 1 kHz. The dielectric loss tangent (tan δ) was found to decrease with increasing PZT content and the tan δ value of 80% PZT composite is 0.06. Parallel and series models were also compared to the dielectric measurement results. For the hysteresis measurements, the ferroelectric hysteresis loops can be seen for all composites. The “instantaneous” remnant polarization (P_ir) was found to increase with increasing PZT content from 3.20 to 4.28 μC/cm² at 90 Hz when PZT volume content used was 60% and 80% respectively.     

Dielectric and piezoelectric properties of 1–3 non-lead barium zirconate titanate-Portland cement composites

Non-lead barium zirconate titanate (BZT)-Portland cement (PC) composites have been seen as promising new non-lead composites. This paper reports research work on the dielectric and piezoelectric properties of 1–3 non-lead barium zirconate titanate (BZT)-Portland cement (PC) composites. The 1–3 non-lead composites with different BZT contents at 40–70% by volume were fabricated by the dice-and-fill method. The results show that the dielectric loss of the 1–3 non-lead composite was lowest at 0.08 at 70% BZT composites. The models are applied for the calculation with the dielectric constant, piezoelectric coefficient and piezoelectric voltage constant and the results were found to fit closest to that of the parallel model. At 70% BZT content or higher, piezoelectric coefficient was found to have values higher than 130 pC/N. In addition, the new 1–3 non-lead composites can be tuned to an ideal compatible value that match the requirement of concrete structure.     

Crystal structure and dielectric properties of barium titanate–kaolinite composites

Barium Titanate–Kaolinite composites were prepared systematically by conventional solid-state method. The crystal structure and dielectric properties of samples were investigated by XRD and dielectric measurements, respectively. XRD results show that new phase BaAl₂Si₂O₈ was formed as kaolinite added into BaTiO₃. The 10 wt% kaolinite addition led to a considerable reduction in sintering temperature and a strong densification. The dielectric constant of BaTiO₃–Kaolinite composites tended to be stable with increasing of kaolinite content.     

Dielectric and ferroelectric hysteresis properties of 1–3 lead magnesium niobate–lead titanate ceramic/Portland cement composites

In this work, lead magnesium niobate–lead titanate (PMN–PT) ceramic was cut and filled with Portland cement (PC) to produce 1–3 connectivity PMN–PT/PC composites. Dielectric and ferroelectric hysteresis properties of these composites with PMN–PT ceramic volume content of 60% were investigated. Room temperature dielectric constant (?_r) at 1 kHz of the PMN–PT/PC composite was found to be ≈1500. At higher frequency (20 kHz), the dielectric constant was reduced to the value of ≈1300. Ferroelectric (polarization–electric field) hysteresis loops at 10–90 Hz and varying electric field were measured. The “instantaneous” remnant polarization (P_ir) at 50 Hz and at the electric field of 7 kV/cm of the PMN–PT/PC composite was found to be ≈10 μC/cm². These values of 1–3 composites therefore are promising when compared to previous results of composites at similar conditions.     

Pyroelectric properties of Mn-doped lead zirconate–lead titanate–lead magnesium niobate ceramics

The pyroelectric properties of MnO₂ doped compositions in the Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃–PbZrO₃ system have been investigated for an uncooled pyroelectric infrared detecting application, looking primarily at compositions in the PbZrO₃-rich corner of the phase diagram. A processing route from the metal oxides through to the poled ceramic has been developed, which has reduced the size and frequency of defects in the sintered ceramic necessary for producing thin (∼200 μm) ceramic wafers. The electrical properties relevant to the pyroelectric application (dielectric constant, tanδ and pyroelectric coefficient) have been surveyed with respect to composition to produce the best values of the pyroelectric ‘figure of merit’ F_D=p/{c′(εε_otanδ)^1/2} at room temperature. The effects of compositional changes in the ceramic on the two phase transitions from: the ferroelectric low temperature to ferroelectric high temperature phases (F_R(LT) to F_R(HT)) and the ferroelectric high temperature to paraelectric phases at the Curie point have also been investigated. The consequential changes of the electrical properties are reported. The resisitivity of the ceramic proved insensitive to either the amounts of excess lead or manganese doping levels.     

Properties of CNTs-modified lead-free BCTS ceramic–Portland fly ash cement composites

Fly ash (FA) is widely used as a supplementary cementitious material in the production of Portland cement concrete. The effect of addition of carbon nanotubes (CNTs) and FA on the properties of barium calcium stannate titanate (BCTS) ceramic–Portland FA cement composites was investigated. These composites have potential for use as sensors and transducers in the monitoring of structural health in concrete structures containing FA. CNTs were found to have filled the pores of the composites. All composites showed good compatibility with the concrete mix. The dielectric constant and electrical conductivity of composites were in the range 200–257 and 1.04 × 10^–6 to 1.66 × 10⁻⁶ S/m, respectively. The presence of FA in composites increased the piezoelectric voltage coefficient (g₃₃). Adding CNTs increased the piezoelectric charge coefficient (d₃₃), thickness electromechanical coupling coefficient (K_t), and also g₃₃ but decreased mechanical quality factor (Q_m), which is related to good for the receiving sensor and transducer application. CNTs can improve the properties of these composites and composite with FA content at 10 vol.%, and CNTs at 1 vol.% exhibited the highest compressive strength and piezoelectric values (d₃₃ = 44 pC/N, g₃₃ = 20.21×10^–3 V m/N, and K_t = 18.9%), along with higher g₃₃ values, than pure BCTS ceramic.     

Structural,piezoelectric and dielectric properties of PSLZT–PMnN ceramics

Pb_0.94Sr_0.05La_0.01(Zr_0.54Ti_0.46)_0.9975O₃–Pb(Mn_1/3Nb_2/3)O₃ (PSLZT–PMnN) ceramics with pure perovskite structure were prepared by conventional mixed oxide method. The influence of PMnN on the structural, dielectric and piezoelectric properties was investigated. The experimental results showed that the perovskite structure changed from tetragonal to rhombohedral symmetry and the Curie temperature decreased gradually with the increase of PMnN. The composition with 3 mol% PMnN exhibited favorable properties of Q_m (400), d₃₃(660 pC/N), k_p (0.60), K^T (1940), tan δ (0.90%) and T_C (247 °C), exhibiting potential usage for piezoelectric actuator and sensor applications.     

Dielectric properties of barium titanate–molybdenum composite

The barium titanate–molybdenum composites were prepared through solid state reaction method in argon atmosphere. The microstructure, resistivity, and dielectric properties of the composites were investigated. XRD results indicated that chemical reactions between barium titanate (BaTiO₃:BT) and molybdenum (Mo) have taken place during sintering, resulting in the formation of BaMoO₄ (BM) and BaTi₂O₅ (BT₂). The resistivity decreased with the increasing amount of Mo in the composites. The composites (when x = 5 and 20 wt.%) showed lower dielectric constant than pure BaTiO₃, especially, the dielectric constant (when x = 20 wt.%) reached a minimum value (<10⁴), while composites (when x = 10 and 15 wt.%) showed rather high dielectric constant at temperatures range from 25 °C to 160 °C. The dielectric constant of the composite gradually decreased with increase in frequency at the room temperature. The dielectric constant of composite (when x = 5 wt.%) comes up to 10⁴, and the T_c (Curie temperature) of the composite was relatively higher than that of BT (120 °C).     

Enhanced piezoelectric properties of barium titanate–potassium niobate nano-structured ceramics by MPB engineering

Barium titanate (BaTiO₃, BT)–potassium niobate (KNbO₃, KN) (BT–KN) nanocomplex ceramics with various KN/BT molar ratios were prepared by the solvothermal method. From a transmittance electron microscopy (TEM) observation, it was confirmed that KN layer thickness of the BT–KN nanocomplex ceramics was controlled from 0 to 44 nm by controlling KN/BT molar ratios. Their dielectric constants were measured at room temperature and 1 MHz, and a maximum dielectric constant of around 400 was measured for the BT–KN nanocomplex ceramics with a KN thickness of 22 nm. TEM observation revealed that below KN thickness of 22 nm, BT/KN heteroepitaxial interface was assigned to the strained interface while over 22 nm, the interface was assigned to the relaxed one. These results suggested that the strained heteroepitaxial interface could be responsible for the enhanced dielectric constants.     

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.     

Design,fabrication and properties of 1–3 piezoelectric ceramic composites with varied piezoelectric phase distribution

Here the 1–3 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution were designed. The dielectric, piezoelectric and electromechanical properties of the composites were studied. The results indicate that the composite with varied distribution of piezoelectric ceramic has large relative permittivity, piezoelectric strain constant and electromechanical coupling coefficient at the thickness vibration mode. The composites with varied distribution of matrix phase have larger piezoelectric voltage constant, smaller mechanical quality factor and acoustic impedance value than those with varied distribution of piezoelectric ceramic phase. The electromechanical coupling property of the composites at the planar vibration mode shows obvious dependence on matrix phase distribution. The novel piezoelectric composites show potential applications in fabricating ultrasonic transducers with specific surface vibration amplitude.     

Phase formation and transitions in the lead nickel niobate–lead zirconate titanate system

Despite the many previous studies of the synthesis and characterization of several perovskite ferroelectric materials which have potential applications in electronic and medical diagnostic devices, the synthesis and phase formation of the whole series in the solid solution of (1 ? x)Pb(Ni_1/3Nb_2/3)O₃–xPb(Zr_1/2Ti_1/2)O₃ (PNN–PZT) system has rarely been studied. In this work, the phase formation, morphology, particle size and chemical composition of perovskite powders in the (1 ? x)PNN–xPZT system were investigated. Powders were prepared by a modified mixed-oxide synthesis route for various chemical compositions under different calcination temperatures. It is found that the perovskite phase undergoes a pseudo-cubic to tetragonal transition as composition changes. The degree of spherical shape and agglomeration were observed to increase with increasing PZT content.     

Synthesis,dielectric and relaxation behavior of lead free NBT–BT ceramics

The 0.94(Na_0.5Bi_0.5TiO₃)–0.06BaTiO₃ ceramics have been prepared by the conventional solid state reaction method. Structural analysis of the prepared ceramic was made by means of room temperature XRD, FT-IR and Raman spectra. The formation of perovskite structure is confirmed by XRD and Raman studies. The dependence of dielectric constant on temperature for various frequencies (100 Hz–1.2 MHz) has been determined. The diffuse transition is observed in the variation of dielectric constant and it provides evidence for the relaxor characteristics. The relaxation mechanism of the prepared ceramic is also discussed in detail by using Debye, V–F and Power law relations and the suitable model was predicted by means of goodness of parameter. This is the first time the relaxation process is discussed for the lead free system to the best of our knowledge. High piezoelectric properties with d₃₃=206 pC/N are observed in the present system.     

Structural,morphological, magnetic hysteresis and dielectric properties of cobalt substituted barium–lead hexagonal ferrites for technological applications

M-type, Ba_0.4Pb_0.6Fe_12-xCo_xO₁₉ (x = 0.00, 0.10, 0.20, 0.30, 0.40) hexaferrites, synthesized using citrate gel auto combustion method, and heated at 950 °C, 4 h for lossless applications. XRD analysis shows the development of the M-phase, along with PbM and hematite. The microstructural analysis reveals the stacking clusters of hexagonally shaped platelets. TEM image and SAED pattern of x = 0.3 composition shows polycrystalline nature and formed particles observed to fused with neighbouring particles. M − H loops of all samples reveal hard magnetic behaviour and possess multi-domain structure. The maximum saturation magnetization of 55.427 A m²/kg is observed in x = 0.10 composition and coercivity of prepared hexaferrites was found to vary from 0.058 T to 0.390 T. The cobalt substitution has a strong influence on the dielectric properties of prepared hexaferrites. The value of ac conductivity increases with cobalt substitution from x = 0.00 to x = 0.10, and followed by a reduction from x = 0.10 to x = 0.40. The same trend is observed for the dielectric constant. The low value of loss tangent for all compositions shows apt scope for lossless application.     

The effect of grinding process on mechanical properties and alkali–silica reaction resistance of fly ash incorporated cement mortars

The effect of fineness of fly ash on mechanical properties and alkali–silica reaction resistance of cement mortar mixtures incorporating fly ash has been investigated within the scope of this study. Blaine fineness of fly ash has been increased to 907 m²/kg from its original 290 m²/kg value by a ball mill. Test samples were prepared by replacing cement 20, 40 and 60%, with finer and coarser fly ashes and kept under standard and steam curing conditions until testing. Test results showed that grinding process improved the mechanical properties of all samples significantly. The beneficial effect of grinding fly ash, may increase utilization of this by-product in precast and ready-mix concrete industries. Incorporation of fly ash with different fineness values and ratios also decreased the expansions to harmless levels of cement mortars due to alkali–silica reaction.     

Enhanced dielectric constant of acrylonitrile–butadiene rubber/barium titanate composites with mechanical reinforcement by nanosilica

Acrylonitrile–butadiene rubber (NBR), a synthetic rubber having C≡N dipoles, was chosen as a polymer matrix with a higher dielectric constant than other non-polar rubber like silicone rubber or ethylene–propylene–diene monomer. Barium titanate (BaTiO₃), as a ferroelectric material, with a high dielectric constant and low dielectric loss was selected as a main filler to further enhance the dielectric constant of NBR. An effective silane coupling agent (KH845-4), selected from five types of silane coupling agents with different characteristic functional groups, was used to modify the surface of BaTiO₃ particles to enhance its interfacial adhesion to the matrix. Fourier transform infrared spectroscopy (FTIR) was used to verify the successful modification. The addition of BaTiO₃ obviously enhanced the dielectric constants. In particular, an uncommon pattern of dielectric loss has been displayed and analyzed in this paper. Nevertheless, the reinforcing effect of mechanical strength of the NBR/treated BaTiO₃ composites is limited. On this basis, the addition of nanosilica (SiO₂), replacing part of NBR, improved the mechanical strength. Confirmed by scanning electron microscopy (SEM), the SiO₂ and treated BaTiO₃ particles were dispersed well in the NBR matrix. The tensile strength was increased from 4.33 to 6.12 MPa when SiO₂ accounted for 4%. Moreover, the curing characterizations, crosslinking density, resistivity, and oil resistance were evaluated. This composite material can be used in manufacturing electronic devices, which are subjected to oily environments for a long time.     

Properties of a ternary calcium sulfoaluminate–calcium sulfate–fly ash cement

In this paper, cement combinations based on calcium sulfoaluminate cement (CSAC) were developed and the effect of fly ash and the hemihydrate form of calcium sulfate on the properties of the systems was studied. Fly ash (FA), anhydrite (ANH), flue-gas desulfurization gypsum (FGDG) and plaster gypsum (PL) were used to develop appropriate CSAC/calcium sulfate and CSAC/calcium sulfate/addition systems, the hydration of which was studied. Tested properties of cements were the compressive strength and the setting times. The results suggest that the use of fly ash in the presence of anhydrite accelerates the formation of a strong ettringite-rich matrix that firmly accommodated unreacted fly ash particles, both synergistically contributing to a dense microstructure. At a given sulfate content, the use of anhydrite was shown to be favourable in terms of the setting times, heat patterns and strength development compared to the hemihydrate-based formulations.     

Electrical properties of low-temperature-fired ferrite–dielectric composites

The effects of the BaO·(Nd_0.8Bi_0.2)₂O₃·4TiO₂ (BNBT) to NiCuZn ferrite ratio and addition of Bi₂O₃–B₂O₃–SiO₂–ZnO (BBSZ) glass on the sintering behavior, microstructure evolution, dielectric and magnetic properties of BNBT–NiCuZn ferrite composites were investigated in developing low-temperature-fired composites for high frequency electromagnetic interference (EMI) devices. The results indicate that these composites can be densified at 900 °C and exhibit superior dielectric and magnetic properties with the addition of BBSZ glass. The dielectric system used in the ferrite–dielectric composites reported in the previous studies mostly belong to the ferroelectricity group, which are not suitable for use in the high frequency range (>800 MHz) due to the selfresonance frequency limit. In this study, the dielectric constant remains nearly a constant over a wide range of frequencies (100 MHz to 1 GHz) and the magnetic resonance frequencies are larger than 100 MHz for the BNBT + BBSZ glass–NiCuZn ferrite composites. Therefore, the BNBT + BBSZ glass–NiCuZn ferrite composites can be a good candidate material for high frequency EMI device applications.     

Effect of fly ash–gypsum blend on porosity and pore size distribution of cement pastes

Abstract

Abstract

This paper reports results on the porosity and pore size distribution (PSD) of cement paste containing simulated desulphurised waste (SDW). The SDW was chosen due to the variability in chemical composition of real desulphurised waste. The SDW is a combination of fly ash and gypsum. The content of fly ash in the SDW changed from 0 to 100% by weight. The water to binder ratio was 0·5. The binder consists of cement and SDW. Cement in the pastes was partially replaced with 25 wt-% SDW. The porosity and PSD of cement pastes at 28 days of curing is reported. Increasing amount of gypsum does not seem to greatly change the pore volume; however, there is tendency of obtaining coarser pore structure in the presence of gypsum. The compressive strength increases with increasing amounts of gypsum. Correlation between strength and PSD is conducted.