Viscous Polymer Processing Research Articles

Enhanced electric breakdown strength and excellent storing density in BaTiO3‐based ceramic in viscous polymer processing

Enhanced electric breakdown strength and excellent storing density in BaTiO₃‐based ceramic in viscous polymer processing

Superior energy storage performance of Sr0.7Bi0.2TiO3-modified Na0.5Bi0.5TiO3-K0.7La0.1NbO3 lead-free ferroelectric ceramics

Na0.5Bi0.5TiO3 (NBT)-based ceramics exhibit significant potential as energy storage dielectric materials due to their high maximum polarization (Pmax). However, their limited energy storage density significantly restricts their practical applications. To address this, this study optimizes the dielectric energy storage characteristics of lead-free relaxor ferroelectric ceramics based on 0.91Na0.5Bi0.5TiO3-0.09 K0.7La0.1NbO3 (NBT-KLN) by incorporating Sr0.7Bi0.2TiO3 (SBT) relaxor additives. The introduction of SBT helps maintain large polarization and induces local disorderly fields, promoting the formation of polar nanoregions. Subsequently, a viscous polymer processing (VPP) technique was employed to reduce defects and enhance density, markedly improving the breakdown strength (BDS). The findings indicate that the BDS of the optimized 0.30SBT (VPP) ceramics increased to 440 kV/cm, while achieving a high energy storage efficiency (η) of 78 % and an elevated energy storage density (Wrec) of 6.29 J/cm3. Additionally, the 0.30SBT (VPP) ceramics demonstrate excellent temperature stability across a broad temperature range from 30 to 120 °C, making them ideal for long-term operation in variable environments. This study demonstrates superior results compared to previous research, thereby opening up new avenues for developing novel lead-free relaxor ferroelectric ceramics with superior energy storage characteristics.

Enhanced energy storage performance in Pb-free Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3-based relaxor ferroelectric ceramics through a stepwise optimization strategy

This study employed a stepwise optimization strategy, including doping Sr(Ga0.5Nb0.5)O3 (SGN) into 0.65Na0.5Bi0.5TiO3-0.35Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics to modify the composition and a further processing improvement. By introducing Ga3+ and Nb5+ ions with high ionic polarization rates into the B-site, the average polarization of the unit cell was maintained while further inducing local disordered fields and promoting polar nanoregions. The high activity of the polar nanoregions was confirmed using piezoelectric microscopy. The effective energy storage density (Wrec) of 2.73 J/cm³ was obtained when the SGN doping was 6.5 %. Subsequently, the densification of ceramics was improved through viscous polymer processing, thereby enhancing the breakdown strength (BDS). A combined approach of finite element simulation and experimental studies was further utilized to investigate the impact of grain size on the BDS. The stepwise optimization strategy enabled the NBT-SBT-6.5SGNVPP ceramics to achieve the Wrec of 5.2 J/cm3 and efficiency (η) of 85 % under 350 kV/cm. Additionally, the ceramics developed by this strategy possess excellent temperature and frequency stability and pulse discharge performance, making them potential candidates for practical applications.

Superior energy-storage density and ultrahigh efficiency in KNN-based ferroelectric ceramics via high-entropy design

The rapidly advancing energy storage performance of dielectric ceramics capacitors have garnered significant interest for applications in fast charge/discharge and high-power electronic techniques. Simultaneously improving the recoverable energy storage density Wrec and efficiency η becomes more prominent at the present time for their practical applications. Herein, a high-entropy concept is implemented on the (K0·5Na0.5)NbO3 (KNN)-based ferroelectric ceramics to design the high-performance dielectric capacitors. First, the strong lattice distortion can absorb some electric energy during the electrical loading process and result in the delayed polarization saturation. Additionally, the large composition fluctuations induce the weak correlation between polar nanoregions and enhance the η. Finally, the high-entropy design and viscous polymer processing method reduce the grain size and improve the Eb. In consequence, excellent Wrec of 11.14 J/cm3 with high η of 87.1% are achieved under an electric field of 750 kV/cm in the high-entropy component. These results demonstrate that the high-entropy concept is a potential avenue to design the KNN-based high-performance dielectric energy storage capacitors.

Achieving improved dielectric energy storage properties and temperature stability in 0.91Na0.5Bi0.5TiO3-0.09K0.7La0.1NbO3 based ferroelectric ceramics by composition design and processing optimization

In this study, a ternary solid solution was designed by incorporating varying concentrations of the B-site composite perovskite Ba(Mg1/3Ta2/3)O3 (BMT) into 0.91Na0.5Bi0.5TiO3-0.09K0.7La0.1NbO3 (NBT-KLN-based) ferroelectric ceramics to optimize their energy storage performance. The introduction of BMT disrupted the long-range ordered state of the A/B site in the original perovskite structure, resulting in increased structural disorder and enhanced relaxor characteristics. The viscous polymer processing (VPP) method was employed to attain a significantly denser structure. The 0.10BMT-vpp ceramic has ultimately achieved optimal energy storage performance, along with exceptional temperature and frequency stability. It boasts a high dielectric breakdown strength (BDS) of 440 kV/cm, an ultra-high effective energy storage density (Wrec) of 6.7 J/cm3, and an energy storage efficiency (η) of 82%. Moreover, the 0.10BMT-vpp ceramic exhibits robust pulse performance, characterized by an ultra-fast discharge time (t0.9) of only 77 ns. Furthermore, within the temperature range of −66 °C–354 °C, the temperature coefficient of capacitance (TCC) of the 0.25BMT ceramics undergoes a variation of no more than ±15%, in compliance with X9R specifications (−55 °C–200 °C). The introduction of BMT endows NBT-KLN-based ceramics with remarkable temperature stability and comprehensive energy storage performance, making it a ceramic material with practical potential for industrial applications.

The enhancement of energy storage performance of BaTiO3–Bi(Mg0·5Ti0.5)O3 Pb-free ceramics via an optimized viscous polymer process route

In this study, the viscous polymer processing (VPP) technique is implemented to optimize the characteristics of bulk (1-x)BaTiO3-xBi(Mg0·5Ti0.5)O3 (BT-xBMT) lead-free relaxor ferroelectric ceramics, with a focus on enhancing the recoverable energy storage density (Wrec), improving breakdown strength resistance (Eb), and increasing storage efficiency (η). The influence of polyvinyl alcohol (PVA) inclusion in the VPP process on the resulting dielectric ceramics is thoroughly investigated, covering rheological, dielectric, and ferroelectric properties. The results reveal that a gradual increase in PVA quantity during the VPP process effectively improves the density of ceramic blanks. However, an excess of PVA leads to void formation in the ceramic blanks post-debinding, hindering the achievement of a dense structure in the final ceramics and causing performance degradation. The resulting BT-0.405BMT-40 wt% PVA ceramic showed excellent storage performance, with Wrec, η, and Eb of 6.55 J/cm3 81.45 %, and 480 kV/cm, respectively. In comparison to bulk BT-0.405BMT ceramics, there is a notable 2.47-fold increase in Wrec and a 1.92-fold increase in Eb, accompanied by a substantial improvement in η. Moreover, the BT-BMT-40 wt% PVA ceramic exhibits favorable temperature stability (30–150 °C), frequency stability (1–50 Hz), and commendable charge/discharge performance.

An ultrahigh energy storage efficiency and recoverable density in Bi0.5Na0.5TiO3 with the modification of Sr0.85La0.1TiO3via viscous polymer process

Currently, the development of dielectric ceramic capacitors is restricted by the contradiction between high efficiency and high recoverable density. Therefore, a novel strategy was designed to achieve a superior balance between them. Firstly, introducing Sr0.85La0.1TiO3 can enhance the content of the weak polar phase (P4bm) to become the main component, which can optimize the relaxor behaviour and improve efficiency. Then, the electric breakdown strength was effectively enhanced by grain refinement and viscous polymer processing. Finally, a high recoverable energy density of ∼5.3 J/cm3 and an excellent efficiency of ∼92.2% were attained in 0.9Bi0.5Na0.5TiO3-0.1Na0.8Sr0.1NbO3 ceramic with the addition of 0.35Sr0.85La0.1TiO3 after viscous polymer processing. The piezoelectric force microscope had been applied to prove the high activity of the polar nanoregions and finite element analysis was adopted to explain the reasons for the enhancing electric breakdown strength. In addition, this ceramic exhibits good temperature and frequency stability, and a fast discharging rate of 0.11 μs, making it a potential candidate for the actual application.

Excellent dielectric energy storage properties of barium titanate based Pb-free ceramics through composition modification and processing improvement

To acquire electric capacitors with enhanced energy storing performance, a composition embellishment and process improvement strategy were adopted. A serial of lead-free (Ba0.875Bi0.125) (Li0.0625Nb0.0625Ti0.875)O3(BBLNT) ceramics were prepared via both conventional solid-state method and viscous polymer processing technology (VPP). The BBLNT-VPP ceramics achieved an ultrahigh energy storing density of 5.34 J/cm3 and a reasonable efficiency of 88% at 470 kV/cm. In addition, the ceramics have particularly extraordinary temperature stability of Wrec2.8 J/cm3, △η2.5% over 30–150 °C, as well as excellent frequency stability with Wrec3.46 J/cm3, η88%, △Wrec±2.7% and △η±4% in the range of 5–300 Hz. Meanwhile, the power density of the ceramic remained above 84.04 MW/cm3 when the temperature was increased from room temperature to about 150 °C, indicating the ceramics possess great promise. Therefore, the BBLNT-VPP ceramics with excellent properties obtained in this work can be potentially applied in dielectric capacitors.

The study of rheology, dielectric, ferroelectric, energy storage properties of Mg-doped Na0.425Bi0.425Ca0.15TiO3 lead-free ceramics through a viscous polymer process

Lead-free relaxor ferroelectric ceramics 0.95Na 0.425 Bi 0.425 Ca 0.15 TiO 3 -0.05 Mg with different polyvinyl alcohol contents (NBCT-Mg- x PVA) were prepared by viscous polymer processing to generate high density and induce high breakdown strength (BDS) and high recoverable energy storage density ( W rec ). The rheology properties of the ceramic pastes had been systematically studied. The content of PVA has exhibited a great influence on the microstructure and property of ceramics. Through the analysis of ceramics with different PVA contents, it is found that the less PVA content, the less pores and greater BDS on the premise of film formation. The related other electrical performances of the resulting ceramics have also been performed. Especially for the NBCT-Mg-0.4PVA ceramics, the BDS of it reached as high as 320 kV/cm, and the W rec was 4.51 J/cm 3 , which also exhibited excellent temperature stability (30–135 °C) and frequency stability (0.2–50 Hz), as well as good stability during charged-discharged process and achieve high power density.

Energy storage performance of 0.55Bi0.5Na0.5TiO3-0.45SrTiO3 ceramics doped with lanthanide elements (Ln = La, Nd, Dy, Sm) using a viscous polymer processing route

Lead-free bismuth sodium titanate-strontium titanate (NBT-ST) dielectric ceramic materials have been extensively investigated energy storage materials because of their relaxor characteristics. In this study, four different lanthanide elements were introduced into the ferroelectric NBT-ST ceramic to improve their relaxor properties. The introduction of the lanthanide resulted in an increase in disorder at location A within the perovskite lattice and improved relaxor characteristics, leading to a stored energy density of more than 3.5 J/cm3. In particular, an ultrahigh recoverable stored energy density of 4.94 J/cm3 and efficiency of 88.45% were achieved at 440 kV/cm when the NBT-ST ceramic was modified with neodymium. The modified ceramic also exhibited good thermal stability in the range of 30–120 °C, as well as a fast discharge time of ∼153 ns, indicating that Nd-incorporated NBT-ST is a promising candidate for electrical energy storage ceramic.

Enhancement of energy storage performance in lead-free barium titanate-based relaxor ferroelectrics through a synergistic two-step strategy design

Dielectric capacitors are widely used because of their advanced performance, including superior power density and high charge–discharge speed. Nevertheless, limitations in energy-storage density (Wrec), efficiency (η) and thermal stability hinder their practical application. Herein, these concerns are addressed using a synergistic two-step strategy of designing the composition of Bi(Zn2/3Nb1/3)O3 and optimizing the preparation for viscous polymer processing (VPP), thus achieving domain engineering, enhanced relaxor behavior, and improved breakdown strength (Eb) in (Ba0.8Sr0.2)TiO3-based ceramics. The broadening of the permittivity peak and highly dynamic polar nanoregions (PNRs) are correlated to expected relaxation characteristics, as indicated by the brightness of atomic position and calculated spontaneous polarization vectors determined through transmission electron microscopy. The relatively small grain size and increased band gap, verified through scanning electron microscopy and ultraviolet − visible spectrophotometry, contribute to the Eb. A prominent Wrec of 5.16 J/cm3 under 540 kV/cm and excellent temperature stability (Wrec = 3.6 J/cm3, η = 92.8%, 20–120 °C) are achieved in 0.91(Ba0.8Sr0.2)TiO3 − 0.09Bi(Zn2/3Nb1/3)O3 ceramics formed by VPP (BZN9VPP). The material possesses an exceptional current density of 647.56 A/cm2, a power density of 113.32 MW/cm3, and a rapid discharge speed of < 60 ns. The comprehensive outstanding performance supports the great potential of this sample for application in pulsed power capacitors.

Ultrahigh dielectric breakdown strength and excellent energy storage performance in lead-free barium titanate-based relaxor ferroelectric ceramics via a combined strategy of composition modification, viscous polymer processing, and liquid-phase sintering

BaTiO3 (BT)-based lead-free ceramics are regarded as one kind of prospective candidates for next generation pulsed power capacitors due to their environmentally friendly and relatively high energy storage properties. Nevertheless, BT-based ceramics are still suffering from their small recoverable energy storage density (Wrec < 3 J cm−3) and relatively low electric breakdown strength (BDS < 350 kV cm−1). Herein, we proposed a combined strategy via composition modification, viscous polymer processing, and liquid-phase sintering into BT-based ceramics to improve their BDS and Wrec. Both an ultrahigh BDS (>410 kV cm−1) and a large Wrec (3.54 J cm−3) are achieved in Sr0.7Bi0.2TiO3 and Li2CO3 modified BT ceramic simultaneously. High Wrec (>2.5 J cm−3 at 300 kV cm−1) with small variation is maintained over a wide temperature range (30–150 °C) and frequency range (0.1–100 Hz), demonstrating very excellent temperature and frequency stability. The recorded ultrahigh BDS with high Wrec achieved in this work indicates that our combined strategy is effective to elevate the electric energy storage performances of BT-based dielectric ceramics and could be further generalized to other ceramic materials for the applications of advanced pulsed power capacitors.

Laser Patterned ZNO Substituted Calcium Phosphate Scaffolds via Viscous Polymer Processing for Bone Graft

Polymer dough processing is a method which can easily overcome this problem. In current study ZnO doped calcium phosphate (Zn-CaP) micropatterned scaffold was explored through viscous polymer processing route. Zn-CaP nanopowder was synthesized using the wet chemical route. It was characterized using SEM, TEM, XRD and EDX. Highly ductile micro-patterned bone grafts were constructed using ZnO doped calcium phosphate scaffolds using roll milling followed by Laser machining. It was kept for cell culture and cytocompatibility using MTT, DNA quantification, and ALP assay. Hemolysis and blood cell aggregation assay was conducted for in vivo applicability. The cellular growth was also observed using fluorescence microscopy, live-dead assay, and SEM. Further gene expression was analyzed using PCR studies which showed osteogenic differentiation of bone marrow-derived stem cells without any supplemented media. The material showed a significant zone of inhibition against both gram positive and negative bacteria. Selective cellular growth was observed at micropatterned zone.

Dimension dependence of thickness resonance behavior of piezoelectric fiber composites

Aperiodic arrangement PZT5 fiber/epoxy resin 1-3 piezoelectric composites were fabricated by viscous polymer processing. The impedance spectra were used to discuss the radial and thickness resonance models dependent on the size of 1–3 composites. The aspect ratio t/d is found critical to the resonance parameters. As the aspect ratio t/d reducing, the mechanical quality factor Qm would decrease, the frequency constant Nt and the acoustic impedance Z increasing. In general, the composites showed nearly a pure thickness mode with high anisotropy coefficient (kt/kp ∼ 1.38–2.75) and low acoustic impedance (Z ∼ 9.5–11.7 Mrayl) superior to those of monophasic PZT5 materials that have potential applications in medical ultrasonic transducers.

Square cross-section piezoelectric fiber composites: structure and ferroelectric properties

Square cross-section lead zirconate titanate (PZT5) fibers were fabricated by viscous polymer processing. Fibers were perpendicularly arranged in glass tubes and infiltrated with bisphenol-A epoxy resin E51 to form 1–3 composite structures. Phase, micromorphology, mechanical properties and electric properties were identified for fibers and composites. As a result, PZT5 ceramic fibers sintering at high temperature above 1280 °C have pure trigonal perovskite phase and side length of ~300 μm. A brittle broken mechanism was put forward by the linear stress–strain curves of PZT5 fibers. 1–3 composites with 30 % fiber volume fraction demonstrated closed and saturated P–E loops, high remnant polarization P r of 15.94 μC/cm2 and low coercive field E c of 0.91 kV/mm. Moreover, the composites performed high piezoelectric strain constant d 33, piezoelectric voltage constant g 33 and high anisotropy parameters k t/k p. The acoustic impedance Z was about one-third of PZT5 ceramics. The above performances of PZT5 composites showed an excellent application prospect in the fields of ultrasonic medical imaging systems and nondestructive testing.

Temperature-Dependent Properties of a 1–3 Connectivity Piezoelectric Ceramic–Polymer Composite

Abstract In this work, the 1–3 connectivity piezoelectric ceramic–polymer composites have been fabricated by a viscous-polymer processing, where 0.90Pb(Zr0.52Ti0.48)O3–0.05Pb(Mn1/3Sb2/3)O3–0.05Pb(Zn1/3Nb2/3)O3 (PZT–PMS–PZN) fibers with 0.5 volume fraction were aligned in epoxy matrix. The sintered PZT fibers, with average diameter of 300 μm and aspect ratio (height/diameter) higher than 3, all showed a pure perovskite phase structure and highly dense morphology. The dielectric, piezoelectric, ferroelectric properties and the vibration modes of the 1–3 composites were measured and demonstrated in comparison with that of the monolithic piezoelectric ceramics. The results confirmed that the 1–3 composites possessed a low acoustic impedance (Z) of 13 MRayl and a high thickness coupling coefficient (k t) of 0.59, in addition, only single thickness vibration mode with the resonance frequency over 1.5 MHz was observed. With temperature elevation, the properties including dielectric constant εr , k t, the ratio of k t to k p (k t/k p) and the acoustic impedance (Z) increase, while the planar electromechanical coupling coefficient (k p) show opposite temperature dependence. Under test temperature of 100°C, the 1–3 composites still present excellent temperature stability with increased k t/k p ratio up to 3.6. The researches on temperature-dependent properties of the 1–3 composites are critical for improving its applications in various environments.

A comparative study of viscous polymer processed ceramics based on aqueous and non-aqueous binder systems

Lead zirconate titanate (PZT) is an important piezoelectric material which has wide range of applications as sensors, actuators and transducers. Various forms are required for different devices applications. In this work, extrusion and press forming of PZT ceramic rods and thick films produced via a viscous polymer processing (VPP) route have been investigated. The relationships between the rheology, microstructure and formability of both an aqueous and a non-aqueous polymer binder system have been compared. The non-aqueous PVB system exhibits substantially higher bulk yield stress during plug die flow and higher biaxial extensional stress during squeeze film flow compared to the aqueous PVA system. Discussion of the results is based on differences in the adsorption of the polymer onto the PZT particles and the migration behaviour of the polymer/solvent phase in the two systems.

Fabrication of three-dimensional inter-connective porous ceramics via ceramic green machining and bonding

A novel method is demonstrated to fabricate three-dimensional inter-connective porous ceramics with engineered structures. The method is based on machining and bonding of ceramic green sheets. The ceramic green sheets were processed via a viscous polymer processing (VPP) route using thermoplastic (polyvinyl butyral) as a binder, which showed good machinability and surface finishing quality. The experimental results also revealed that an appropriate solvent and adequate applied pressure were critical to ensure good interfacial bonding between green ceramic sheets and subsequent integrity of the sintered three-dimensional inter-connective ceramic bodies. The architectures and microstructures of fabricated ceramic bodies can be readily controlled by the characteristics of the green body and the computer numerically controlled machining conditions.

Fabrication of niobium doped Pb(Zr,Ti)O 3 fibers by viscous polymer processing

A technique based on viscous polymer processing (VPP) was described, which can produce high ceramic content green fibers. PZT-5 ceramic powders were ball milled to get high dispersibility. The slurry prepared for VPP was a composition of PZT-5 powder, PVA binder and glycerin. High ceramic content PZT-5 fibers were extruded with the slurry. The results show that the ceramic powders have fine mean particle size of 0.54 μm, high specific surface area of 3.55 m 2/g and zeta potential of 8.81 mV after 16 h milling. The fibers sintered at 1 280 °C for 4 h have pure perovskite structure and grains of 2–5 μm, in size, with little pores or cracks. The ultimate tensile strength of sintered fibers is up to 13.84 MPa compared with 2.88 MPa of green fibers. The remnant polarization ( P r) and coercive field ( E c) of the fibers are 50.65 μmC/cm 2 and 2.45 kV/mm, respectively. This fiber can withstand an electric field of 9 kV/mm higher than the ceramic (5 kV/mm), which shows high directional and compact qualities.

1–3 connectivity piezoelectric ceramic–polymer composite transducers made with viscous polymer processing for high frequency ultrasound

Potential applications of high frequency ultrasound exist because of the high spatial resolution consequent upon short wavelength. The frequencies of interest, typically from 25 MHz upwards, are easily supported by modern instrumentation but the capabilities of ultrasonic transducers have not kept pace and the transducers in high frequency commercial ultrasonic systems are still made with single-phase crystal, ceramic or piezopolymer materials. Despite potential performance advantages, the 1–3 connectivity piezoelectric ceramic–polymer composite materials now widely used at lower ultrasonic frequencies have not been adopted because of manufacturing difficulties. These difficulties are centred on fabrication of the 1–3 piezoceramic bristle-block comprising tall, thin pillars upstanding from a supporting stock. Fabrication techniques which have been explored already include injection moulding, mechanical dicing, and laser machining. Here, we describe an alternative technique based on viscous polymer processing (VPP) to produce net shape ceramic bristle-blocks. VPP produces green-state ceramic with rheological properties suitable for embossing. We outline how this can be created then report on our work to fabricate PZT bristle-blocks with lateral pillar dimensions of the order of 50 μm and height-to-width ratios of the order of 10. These have been backfilled with low pre-cure viscosity polymer and made into complete 1–3 piezocomposite transducer elements. We outline the performance of the transducers in terms of electrical impedance and pulse-echo behaviour and show that it corresponds well with computer modelling. We conclude that VPP is a promising technique to allow the established advantages of piezocomposite material to be exploited at higher frequencies than have been possible so far.