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Cold Sintering was applied to densify a Potassium-Sodium Niobate solid solution composition, 0.5KNbO3-0.5NaNbO3 (KNN); the process uses a transient chemical sintering aid, moderate pressure (400 MPa), and temperatures between 230–300 °C to obtain ceramics of ∼92 to 96 % theoretical density. Typically, sintering temperatures between ∼1000−1050 °C are required to density KNN using conventional methods. In this paper, the densification was investigated during heating, particularly the shrinkage in the first 60 min of the cold sintering process. The low-field dielectric and electrical properties of the resulting ceramics were found to be comparable to conventionally sintered KNN. Electric fields up to 80 kV/cm could be applied, however the ceramics showed pinched hysteresis loops, even after poling over a wide range of temperatures and electric fields. A Rayleigh analysis was used to investigate domain dynamics and high reversible permittivity. The irreversible behavior was an order of magnitude lower than in conventionally sintered KNN, likely associated with defect pinning of ferroelectric domains. A Transmission Electron Microscopy (TEM) study revealed a high density of line defects in most grains; dislocations in the grains limit poling and domain wall movement, thus suppressing both the piezoelectric properties and the hysteresis. Furthermore, TEM observations indicated crystalline grain boundaries that were faceted with terrace kink ledges. These observations point to the importance of the initial powder optimization and grain boundary diffusion when using cold sintering to prepare ceramics that are intended to show bulk cooperative properties such as ferroelectricity. The impact of limited high temperature homogenization of bulk diffusional processes is discussed.

Controlling the grain growth and grain boundary morphology is of great importance in the manipulation of electrical properties of electro-ceramics. However, it has been a challenge to achieve dense varistor ceramics with grain sizes in submicrons and nanometers using conventional thermal sintering at high temperatures. Here we present a strategy to fabricate dense ZnO based ceramics with controlled grain growth and thin grain boundaries using cold sintering process (CSP). With CSP, the sintering temperature of ZnO based ceramics dramatically drops from 1100 °C to 300 °C. The Bi2O3, Mn2O3, and CoO dopants suppress the grain growth of ZnO under CSP conditions, and Bi-rich intergranular films (2−5 nm) can be observed along grain boundaries. The cold sintered ZnO-Bi2O3-Mn2O3-CoO ceramic shows a non-linear coefficient of 33.5, and a superior breakdown electric field of 3550 V/mm. This work thus demonstrates that CSP is a promising technique for designing new submicron-/nano-ceramics with superior performances.

Although cold sintering remains an emerging processing technique, it is noteworthy to consider recent progress in materials that are of interest to electrochemical systems with elevated service temperatures. Here we discuss a broad number of materials ranging from alkali electrolytes for solid state batteries, to oxygen ion conductors for gas sensing. We also discuss the opportunity to co-fire mixed ionic conductors into multilayered devices. Given the low-temperature sintering temperatures with the cold sintering process (CSP), we will discuss some insights into operating ceramics at temperatures near or above their processing temperature.

A novel process was developed for the fabrication of 5–50 µm lead zirconate titanate (PZT) thick films on metal substrates. Tape cast PZT with a methyl cellulose binder was burned out at 275 °C, humidified, and then partially densified at 300 °C by cold sintering with a wet lead nitrate liquid phase. Lamination of the green tape on dense metal foils led to incomplete densification due to constrained sintering. However, when metal foils were replaced with tape cast Cu, fully sintered PZT/Cu/PZT composites were acquired after a secondary heat treatment at 800 °C. The PZT films has a relative permittivity over 500 and a loss tangent ~12% at 100 Hz because of a Cu2O interface between the PZT and Cu presumably formed during the cold sintering process. The polarization-electric field hysteresis loop shows a remanent polarization over 20 µC/cm2, and the e31,f of the samples is -4.7 C/m2.

The use of low-temperature and energy-efficient techniques to fabricate composites with tailored interfaces is currently a topic of growing interest. This study reports the proof of concept of a process to fabricate functional multilayer varistor (MLV) devices below 150 °C. In this MLV device, a small volume fraction of polyetherimide polymer is used to engineer ZnO grain boundaries, and the multilayer composite is cofired with base metal internal electrodes via the cold sintering cofired ceramic (CSCC). The resulting dense nanocomposite MLV and controlled nonlinear current–voltage response of the device confirmed the potential of CSCC. This work also opens up the possibility to fabricate multilayer devices for other types of applications.

Lead indium niobate (PIN)—lead magnesium niobate (PMN)—lead titanate (PT) solid solution in the ratio of 0.26PIN–0.40PMN–0.34PT was fabricated by tape-casting in random and pc textured forms. PIN–PMN–PT was textured using 5 vol% barium titanate templates. The Lotgering factor, f, of 0.26PIN–0.40PMN–0.34PT textured ceramics was approximately calculated as 95%. Quenching from above the Curie temperature down to the room temperature was applied to both random and textured samples, which led to drastic increases in the ferroelectric and piezoelectric properties. The Curie temperature, dielectric constant (er), converse piezoelectric charge coefficient (d 33 * ) and piezoelectric voltage constant (g33) of textured and quenched sample were found to be 223 °C, 2455, 1432 pm/V and 27.60 × 10−3 Vm/N, respectively.

High-performance lead-free piezoelectrics are of interest as alternate materials to confront potential legislative actions on lifting the exemption on lead-based piezoelectric materials. In this work, we demonstrated a highly textured commercial-grade Li- and Ta- modified (Na, K)NbO3 (NKN) lead-free piezoceramic that was sintered under low oxygen partial pressure (pO2) atmospheres using the solid state template grain growth (TGG) method. It was found that a moderate low pO2 condition not only facilitated the reactive template grain growth but also lowered the temperature required for such process. Highly textured NKN with a converse piezoelectric coefficient d 33 * ≈ 680 p m V - 1 was obtained, this remarkable piezoelectric property can be explained by the position of the polymorphic phase boundary of NKN. With considerations on both performance and cost, this work not only presented the potential for NKN to meet the requirement of commercial applications, but also provided an effective processing strategy to utilize low cost base metal inner electrodes in the future.

PZT-based perovskite structure relaxors are very attractive for high power piezoelectric applications. Targeting multilayer co-fired piezoelectric transformers, we developed a PNN-PMW-PZT system [Pb(Ni1/3Nb2/3)O3-Pb(Mg1/2W1/2)O3-0.9Pb(Zr0.5Ti0.5)O3+xMnO2] and used flux materials to decrease the sintering temperature. Systematically investigating the effect of MnO2 content on piezoelectric and dielectric properties, the composition with 0.25 wt% MnO2 hardener exhibited excellent piezoelectric properties after sintering at 1000 °C for 2 h (Qm: 1150, kp: 0.63, d33: 345, tan δ: 0.0040, eT33/e0: 1030). In addition to the compositional development, this work also involved functional tests and high-power characterization of a multilayer piezoelectric transformer utilizing this new ternary system that provided 38 W/cm3 output power density with 92% efficiency and a step-up ratio of 7.

0.62[0.75(Pb(Mg1/3Nb2/3)O3)-0.25(Pb(Yb1/2Nb1/2)O3)]-0.38(PbTiO3) ceramics were successfully textured in [001] via the template grain growth method using 1–7 vol% platelike BaTiO3 (BT) templated (the Lotgering factor of 0.91 at 5 vol% BT). Dielectric spectra indicated a normal ferroelectric behavior without any frequency dispersion and no low-temperature phase transition. The chemically stable BT phase within the matrix gave rise to a composite effect and its relatively inferior properties affected the dielectric and electromechanical properties. The lower TC of the BT decreased the Curie temperature from 226 to 213 °C (with a depolarization temperature of 204 °C). Significantly higher levels of strain (0.33%), narrower hysteresis level (7.7%), higher piezoelectric strain coefficient (660 pm/V), and low-field (

WOS: 000397503100013, In this study, uniform rectangular plate-like perovskite Na0.5Bi0.5TiO3 templates were obtained by molten salt synthesis method in three steps. Perovskite plate-like Na0.5Bi0.5TiO3 templates were synthesized from bismuth-layered Na0.5Bi4.5Ti4O15 by topochemical microcrystal conversion method at the third and final step. The most important point was that the plate-like morphology remained as desired, but templates were obtained in cubic perovskite structure. The Na2CO3 excess in the third step was the main controlling parameter. The crystalline orientation of the particles was investigated by electron backscatter diffraction analysis. The results indicated that the particles are single crystalline in nature. In the case of the 90mol% excess of the stoichiometric Na2CO3 ratio, the NBT platelets had highly regular, rectangular prismatic morphology and single-crystal nature. The structure was also confirmed through high-resolution transmission electron microscope and selected area electron diffraction analysis., Scientific and Technical Research Council of Turkey-TUBITAK [114M518], This work was financially supported by the Scientific and Technical Research Council of Turkey-TUBITAK through the Project no. 114M518.

0.62[0.75(Pb(Mg1/3Nb2/3)O3)–0.25(Pb(Yb1/2Nb1/2)O3)]–0.38(PbTiO3) ceramics were successfully textured in [001] (Lotgering factor of 0.91) using plate-like BaTiO3 templates, for the first time. Samples were densified to 98% of the theoretical density. Significantly higher levels of strain (0.33%) and low-field (

Effect of crystal anisotropy on thermoelectric properties of textured KSr 2 Nb 5 O 15 ferroelectric ceramics is studied for the first time. Temperature dependent conductivity and Seebeck coefficient were measured in directions parallel and perpendicular to the c direction. A transition in electrical conduction from semiconductor to metallic behavior was observed at around 610 K. The power factor was remarkably improved depending on measurement directions such that it was 390 μW/mK 2 in parallel and 283 μW/mK 2 in perpendicular to the c direction at 1120 K. Textured KSr 2 Nb 5 O 15 ceramics are promising candidates to be used as n-type thermoelectric materials at high temperatures and oxidizing environments.

The cold sintering process (CSP) is a technique that enables densification of ceramics and composites at extremely low temperatures (T ​

WOS: 000328471500002, Dimension, shape and materials' properties are the most basic characteristics of a piezoelectric ceramic transducer determining the device performance. In our studies better electromechanical performance was obtained from piezoelectric ceramic itself by creating designs based on built-in amplification mechanisms obtained through the shape and geometry of the transducer, i.e. the macroscale engineering. Piezoceramics in thin hollow shell and fiber forms were fabricated by slip casting and alginate gelation. Additionally, improving materials properties along preferred directions can be achieved through the fabrication of crystallographically textured piezoceramics, i.e. Microscale Engineering. Alginate gelation and templated grain growth was used to produce them., Scientific and Technological Research Council of Turkey (TUBITAK) [MISAG 202, 107M092, 110M627], These studies were conducted with the financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) through the projects: MISAG 202, 107M092, 110M627.

WOS: 000375518700008, Sr0.61Ba0.39Nb2O6 (SBN61) ceramic fibers with a high [001] texture were fabricated by a combination of alginate gelation method and templated grain growth process using acicular Ba2NaNb5O15 (BNN) template particles. The rod-like BNN template particles were prepared by molten salt synthesis method with salt/powder ratio of 2 giving the highest aspect ratio. Fibers were drawn from alginate based slurries without or with 10 wt% BNN template particles. Increasing sintering temperature and time were found to increase the texture. Textured SBN61 bulk ceramics with dimensions in cm scale were fabricated by wet packing a limited number of grain oriented green fibers and sintering the green bulk to obtain a dense, textured bulk ceramic through templated grain growth. A maximum texture fraction, f, of 0.91 was obtained, as measured by Lotgering factor. Increased remnant polarization and electromechanical properties were obtained as a result of this preferred grain orientation. (C) 2016 Elsevier Ltd. All rights reserved., Scientific and Technical Research Council of Turkey (TUBITAK) [110M627]; Turkish Academy of Sciences (TUBA) through the Young Scientists Award Programme (GEBIP), This work was financially supported by the Scientific and Technical Research Council of Turkey (TUBITAK) through the Project no. 110M627 and by the Turkish Academy of Sciences (TUBA) through the Young Scientists Award Programme (GEBIP).

The effect of crystallinity and particle morphology of the submicron barium hexaferrite (BaFe12O19) powders on the magnetic properties was investigated on powders synthesized by solid-state calcination (BHF-c) and molten salt synthesis (BHF-m) methods. Solid-state calcination route was found to yield agglomerated powders with poor crystallinity, whereas molten salt synthesis resulted in well crystallized powders with an anisometric morphology. The saturation magnetization of the BHF-m and BHF-c samples is 59 emu/g, and 56 emu/g at 300 K, and 90 emu/g, and 86 emu/g at 10 K. The temperature dependence of magnetization of the BHF-m is higher and the increase in magnetocrystal anisotropy with decreasing temperature is also steeper than that of the BHF-c due to the higher crystallinity. The magnetocrystalline anisotropy constant, K, calculated from the Stoner–Wohlfarth theory, of the BHF-m and BHF-c powders is 14.24 and 10.14 HA2/kg, respectively. The higher effective anisotropy, Keff of the BHF-m is also confirmed through ferromagnetic resonance measurements. In conclusion, the higher crystallinity, slightly higher particle size and anisometric morphology of the BHF-m particles translated into higher magnetic properties and magnetocrystalline anisotropy.

Highly [00 textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. Fibers were drawn from alginate based slurries without or with 25 and 100wt% KSN template particles. A texture fraction of 0.90 was obtained in the case of 25 wt% and a single crystal like texture was obtained in the case of 100wt%. Piezocomposites with 1-3 connectivity were prepared from the KSN fibers and their electrical and electromechanical properties were investigated. Dielectric constant of 140, piezoelectric charge coefficient of 45 pC/N, remnant polarization of 16.6 μC/cm2 and electric field induced strain of up to 0.035% were obtained from piezocomposites with textured fibers.

A promising n-type thermoelectric oxide, based on the tungsten bronze-structured ferroelectric SrxBa1_xNb2O6-δ (SBN, x~0.61), was investigated to enhance the thermoelectric power factor through templated grain growth (textured poly crystalline). In the reduced SBN textured, both the electrical conductivity (σ) and the magnitude of thermopower (S) are increased in the c axis: σ33 > an and S33 > S11, and consequently, the thermoelectric power factor (PF) increased significantly due to crystal anisotropy and grain boundary density reduction. It was found in randomly oriented polycrystalline ceramics that the thermoelectric properties are dominated by a-axis properties. A ferroelectric-thermoelectric anomaly is observed at 4mm-4/mmm phase transition temperature (TC) and depends on temperature and reduction degree, consistent with our earlier observations in single crystal SBN. Above TC, the carrier transport mechanism is controlled by polaron hopping conduction, and below TC,the behavior depends on the degree of reduction. However, the magnitude of the Seebeck coefficient is dependent on the crystal anisotropy.

Highly [001] textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. Fibers were drawn from alginate based slurries without or with 10 wt% KSN template particles. A maximum texture fraction of 0.96 was obtained. Piezocomposites with 1–3 connectivity were prered from the KSN fibers and their electrical and electromechanical properties were investigated. Dielectric constant of 90, piezoelectric charge coefficient of 60 pC/N, remnant polarization of 10 μC/cm2 and electric field induced strain of up to 0.036% were obtained from piezocomposites with textured fibers.

Lead barium niobate (PBN or PbxBa1–xNb2O6) is a promising tungsten bronze ceramic system that has a morphotropic phase boundary between the orthorhombic and tetragonal phases at x ≈ 0.63, where the spontaneous polarization (Ps ≈ 60–70 μC/cm2) and other ferroelectric properties are known to be higher. However, even textured PBN60 ceramics have low Ps (∼23.9 μC/cm2) and piezoelectric charge coefficient (d33 ≈ 236 pC/N) as compared to the single crystal counterparts. The aim of this study is to control powder processing, green body formation, and sintering conditions to enhance both densification and electrical properties. Therefore, samples were prepared by tape casting methods using single phase PBN60 and reactive mixture of PbNb2O6 and BaNb2O6 powders. Three wt% excess PbO was found to be necessary for densification. Our results showed that undoped PBN60 ceramics reached Ps = 33 μC/cm2, d33 = 305 pC/N, and had a Tc = 340–350 °C. These results are much higher than the reported values in the literature, which can be attributed to the careful ceramic processing such as tape casting (e.g., homogenous green structure), annealing (e.g., control of excess grain boundary phase), and liquid phase sintering (e.g., higher densification).

Textured ceramic fibers were fabricated from the tungsten-bronze type piezoelectric KSr 2 Nb 5 O 15 . Development of crystallographic texture was evaluated through rocking curve analysis and a texture with Lotgering factor of 0.97 was achieved. 1–3 piezocomposites were prepared from the textured fibers and their electrical properties were evaluated. Highly enhanced properties were observed with increasing texture fraction.

Highly [001] textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. The needle-like KSN template particles were prepared by molten salt synthesis method with salt/powder ratio of 2 giving the highest aspect ratio. Fibers were extruded into CaCl2 salt solutions from alginate-based slurries without or with 10 wt% KSN template particles using a nozzle with 2 mm diameter and 80 mm length. Varying sintering temperature from 1300 degrees C to 1450 degrees C and time from 2 to 6 h were found to increase the texture. A maximum degree of orientation, f(00l), of 0.95 was obtained, as measured by Lotgering factor, and a grain orientation distribution, r, of 0.28 was obtained as measured by rocking curve analysis.