Potassium Sodium Niobate Research Articles

Piezoelectric Biocomposites for Bone Grafting in Dentistry.

In this research, Hydroxyapatite-Potassium, Sodium Niobate-Chitosan (HA-KNN-CSL) biocomposites were synthesized, both as hydrogel and ultra-porous scaffolds, to offer two commonly used alternatives to biomaterials in dental clinical practice. The biocomposites were obtained by varying the content of low deacetylated chitosan as matrix phase, mesoporous hydroxyapatite nano-powder, and potassium-sodium niobate (K0.47Na0.53NbO3) sub-micron-sized powder. The resulting materials were characterized from physical, morpho-structural, and in vitro biological points of view. The porous scaffolds were obtained by freeze-drying the composite hydrogels and had a specific surface area of 18.4-24 m2/g and a strong ability to retain fluid. Chitosan degradation was studied for 7 and 28 days of immersion in simulated body fluid without enzymatic presence. All synthesized compositions proved to be biocompatible in contact with osteoblast-like MG-63 cells and showed antibacterial effects. The best antibacterial effect was shown by the 10HA-90KNN-CSL hydrogel composition against Staphylococcus aureus and the fungal strain Candida albicans, while a weaker effect was observed for the dry scaffold.

Lead-free piezoceramic macro-fiber composite actuators toward active vibration control systems

Macro-fiber composite actuators (MFCAs) suffer from strict restrictions on the utilization of lead-containing precursors due to growing environmental concerns. To address this issue, a novel lead-free MFCA based on potassium sodium niobate piezoceramics has been developed using the dice & fill method. The MFCA demonstrates large electric field-induced displacement (31.4 μm over -500‒1 500 V at 0.5 Hz), excellent frequency stability, and a strong linear relationship between the induced displacement and the external voltage amplitude. Meanwhile, unlike lead-based MFCA that requires superposition of a negative dc bias voltage to pursue higher output performance but risks depolarization, lead-free MFCA can achieve larger displacement by superimposing only a positive bias voltage. This device exhibits excellent reliability, maintaining a stable output over 105 electrical cycles. Additionally, a “back-to-back” coupled MFCA has been developed to regulate bidirectional displacement, making it suitable for various practical applications, including active vibration control. This approach has resulted in a 90% vibration reduction and provides new insights into the design of MFCAs, further facilitating their application in active vibration control systems.

Deciphering the role of A-site ions of AZrO3-type dopants in (K, Na)NbO3 ceramics

As one of the most important lead-free piezoelectric candidates, potassium sodium niobate [(K, Na)NbO3, KNN] has gained popularity due to its attractive functional properties, which are much improved by chemical modifications. However, there still remains an insufficient understanding of how these dopants influence the structure and performance of KNN ceramics. Herein, we comparatively studied a series of changes triggered by introducing (Bi0.5Na0.5)ZrO3, BaZrO3, and PbZrO3 into the KNN matrix. The analysis highlights their different roles in modulating the orthorhombic-tetragonal phase transition temperature (TO-T) by considering discrepancies in the electronegativity and radius among Bi3+, Ba2+, and Pb2+ ions. The synergistic effects of the large electronegativity and the small radius of the Bi3+ ion are the key to regulating TO-T, which is relatively unaffected by Pb2+ and Ba2+ ions. Based on experimental results and first-principles calculations, a multi-scale model is proposed to summary the general law of how the electronegativity and radius of the A-site ion in AZrO3-type dopants synergistically affect the phase structure, ferroelectric domains, and electrical properties of KNN ceramics. Therefore, this work helps understand the role of chemical dopants in the structure and performance of KNN ceramics and promote the future composition design for high performance.

Boosting Piezo‐Catalytic Activity of KNN‐Based Materials with Phase Boundary and Defect Engineering

AbstractAlthough the piezo‐catalysis is promising for the environmental remediation and biomedicine, the piezo‐catalytic properties of various piezoelectric materials are limited by low carrier concentrations and mobility, and rapid electron‐hole pair recombination, and reported regulating strategies are quite complex and difficult. Herein, a new and simple strategy, integrating phase boundary engineering and defect engineering, to boost the piezo‐catalytic activity of potassium sodium niobate ((K, Na)NbO3, KNN) based materials is innovatively proposed. Tur strategy is validated by exampling 0.96(K0.48Na0.52)Nb0.955Sb0.045O3‐0.04(BixNa4‐3x)0.5ZrO3‐0.3%Fe2O3 material having phase boundary engineering and conducted the defect engineering via the high‐energy sand‐grinding. A high reaction rate constant k of 92.49 × 10−3 min−1 in the sand‐grinding sample is obtained, which is 2.40 times than that of non‐sand‐grinding one and superior to those of other representative lead‐free perovskite piezoelectric materials. Meanwhile, the sand‐grinding sample has remarkable bactericidal properties against Escherichia coli and Staphylococcus aureus. Superior piezo‐catalytic activities originate from the enhanced electron‐hole pair separation and the increased carrier concentration. This study provides a novel method for improving the piezo‐catalytic activities of lead‐free piezoelectric materials and holds great promise for harnessing natural energy and disease treatment.

Carbon Fiber-Reinforced Piezoelectric Nanocomposites: Design, Fabrication and Evaluation for Damage Detection and Energy Harvesting

Carbon fiber-reinforced polymers (CFRPs) can be used in aging infrastructures as a reinforcement because of their excellent mechanical properties, and they can also be used in the support maintenance and repair work of these structures. However, the development of CFRPs as reinforcement while achieving self-powered damage detection is still challenging. Herein, a sodium potassium niobate (KNN) nanoparticle-filled epoxy (KNN–EP) plate was fabricated and combined with advanced CFRP electrodes. The obtained composites exhibited dramatically enhanced mechanical properties. In addition, CFRP contributed to the energy harvesting output (peak-to-peak output voltage Vpp = 7.25 mV), which was over 600 % higher than that of the KNN–EP plate. Thus, this composite could work as a force sensor for damage detection. In the end-notch bending test, the voltage signals generated by CFRP/KNN–EP composite accurately corresponded to the crack growth, which could provide the real-time crack state and prediction of fracture occurrence. Therefore, this work provided a new strategy for structural enhancement and kinetic energy harvesting, which can be used to detect damage behavior in infrastructures.

INFLUENCE OF DOUBLE CALCINATION-MILLING ROUTE ON THE STRUCTURAL AND MICROSTRUCTURAL PROPERTIES OF LEAD-FREE K0.5NA0.5NBO3 (KNN) CERAMICS

Potassium sodium niobate (KNN) has always been one of the most potential candidates to replace lead-based piezoelectric ceramics due to its strong piezoelectric properties and environmentally friendly composition. A strong piezoelectric property is constantly influenced by the sample's densification as well as its microstructural characteristics. One of the current main issues with this KNN lead-free piezoelectric material is the difficulty in creating high-density samples by conventional preparation and sintering. Thus, KNN lead-free ceramics were synthesised using an improved solid-state method by introducing the double calcination-milling route to this process. The outcome demonstrates that, despite the presence of additional KNN secondary phases, the double calcination-milling approach contributed to the early creation of the KNN phase. When sintered pellets are subjected to a double calcination milling process, the XRD pattern revealed that the main peaks of the sample are indexed to orthorhombic K0.5Na0.5NbO3. The double calcination KNN pellet have a relative density of 90% densification which is slightly higher than that of single calcination KNN pellet which shows 88% densification.

MXene-functionalized KNN dielectric nanofillers incorporated in PVA nanofibers for high-performance triboelectric nanogenerator

The low surface charge density and consequent unsatisfactory energy conversion efficiency of nanogenerators hinder their capacious utility toward the emerging field of wearable electronics. The strategy of introducing dielectric fillers into a polymer matrix attempts to improve dielectric constant and, thereby, to enhance surface charge density but can hardly yield sufficient energy conversion efficiency. Herein, we report a high performance flexible and compressible triboelectric nanogenerator (FC-TENG) based on a lead-free dielectric material, potassium sodium niobate (KNN), embedded with Ti3C2Tx MXene fillers, blended into poly-vinyl alcohol (PVA) using an electrospinning technique. The role of MXene in dielectric functionalization is to promote the interfacial polarization effect by forming micro-capacitor structures or percolation systems and, thereby, to endow high charge-inducing and charge-trapping capabilities. As a result, the prepared 4 vol. % MXene loaded KNN/PVA nanofibers achieve a higher dielectric constant/dielectric loss factor, which leads to enhanced energy conversion efficiency of FC-TENGs with a maximum power density of ∼2780 mW/cm2. In addition, the selected device was employed into shoe-insoles to demonstrate its ability of capturing biomechanical energy, which reveals its potential to be utilized as a wearable power-source for next generation devices.

ДИЭЛЕКТРИЧЕСКИЕ СВОЙСТВА КЕРАМИК НИОБАТА ТИТАНАТА НАТРИЯ КАЛИЯ

The paper considers the preparation of potassium sodium niobate ceramics doped with titanium in an amount of 5 mol. %. The structure and dielectric properties were investigated in the temperature range 30–650 °C. It is shown that acceptor doping leads to a decrease in the grain size. Violation of stoichiometry in the anionic sublattice contributes to a decrease in the relaxation time of thermal ionic polarization compared to the case of nonstoichiometry in the cationic sublattice.

Potassium sodium niobate-based transparent ceramics with high piezoelectricity and enhanced energy storage density

Lead-free potassium sodium niobate (KNN)-based transparent ceramics are highly desirable owing to their excellent piezoelectricity, and recoverable energy storage density (Wrec) especially for optoelectronic devices. However, it is challenging to achieve all parameters such as efficient light transmittance and excellent piezoelectricity or energy storage performance in a single device. Herein, we report a facile fabrication of transparent ceramic composed of (1 – x)[(Na0.57K0.43)0.94Li0.06][(Nb0.94Sb0.06)0.95Ta0.05]O3-xCaZrO3 (x = 0, 0.01, 0.03, 0.05, 0.07, 0.09 and 0.10) ((1 – x)KNLNST-xCZ) via conventional solid-state reaction method. It has been found that ceramics can retain good light transmission and maintain their piezoelectric properties by adjusting the phase structure and refining the grains to a certain extent. In particular, KNLNST-based transparent ceramic with 0.07CZ modifications demonstrates a high transmittance (T = 73.5% at 1800 nm) and exceptional piezoelectric constants (d33 = 130 pC/N), which is more efficient than reported KNN-based transparent ceramics. More importantly, a significant improvement in grain size refinement is also achieved through the integration of CZ into KNLNST, which allow us to increase the breakdown strength of the ceramics while improving their light transmittance, which result in a high density of energy storage. The highly efficient energy storage performance (Wrec = 4.88 J/cm3) and the higher transparency (T = 75% at 1800 nm) at 0.91KNLNST-0.09CZ ceramic. We believe that this work will provide useful strategies for the development of KNN-based functional ceramics.

Piezoelectric Bioactive Glasses Composite Promotes Angiogenesis by the Synergistic Effect of Wireless Electrical Stimulation and Active Ions.

Insufficient angiogenesis frequently occurs after the implantation of orthopedic materials, which greatly increases the risk of bone defect reconstruction failure. Therefore, the development of bone implant with improved angiogenic properties is of great importance. Mimicking the extracellular matrix clues provides a more direct and effective strategy to modulate angiogenesis. Herein, inspired by the bioelectrical characteristics of the bone microenvironment, a piezoelectric bioactive glasses composite (P-KNN/BG) based on the incorporation of polarized potassium sodium niobate is constructed, which could effectively promote angiogenesis. It is found that P-KNN/BG has exceptional wireless electrical stimulation performance and sustained active ions release. In vitro cell experiments reveal that P-KNN/BG enhances endothelial cell adhesion, migration, and differentiation via activating the eNOS/NO signaling pathway, which might be contributed to cell membrane hyperpolarization induced by wireless electrical stimulation increase the influx of active ions into the cells. In vivo chick chorioallantoic membrane experiment demonstrates that P-KNN/BG shows excellent pro-angiogenic capacity and biocompatibility. This work broadens the current understanding of bioactive materials with bionic electrical properties, which brings new insights into the clinical treatment of bone defect repair.

Comparison of impact from typical additives for phase structure in (K, Na)NbO3-based ceramics

Phase engineering has been widely utilized to promote piezoelectricity in potassium sodium niobate (KNN)-based ceramics via appropriate addition. However, the different impact on phase structure from various additives is still not researched deeply. Herein, the comparison of influence on phase transition temperatures (TR-O, TO-T and TC) is emphasized on from different typically additives [Bi0.5Ag0.5ZrO3 (BAZ), BaZrO3 (BZ), and Sb5+], to reveal the intrinsic essence of structure evolution. The effect on rhombohedral-orthorhombic (R–O) phase boundary can be gained as BAZ > Sb5+>BZ because of the elevating and reducing TR-O with increasing BAZ and BZ when Sb5+ is decreased, respectively. And the influence on orthorhombic-tetragonal (O-T) phase boundary can be manifested as BAZ > Sb5+≈BZ due to the decreasing and little changed TO-T with increasing BAZ and BZ as Sb5+ is reduced, respectively. Both BAZ and BZ additives are more effective on destroying long-range ordered matrix along with lower TC and stronger relaxor behavior with respect to Sb5+, which is induced by strong local structural heterogeneity from more complex composition. Furthermore, the effect of structure evolution on electrical properties is revealed systematically. This work is beneficial to understand the rules of phase boundary formation and promote structure adjustment via component design.

Enhanced dielectric and electrical performance of phosphonic acid-modified tantalum (Ta)-doped potassium sodium niobate (KNaNbO3)-P(VDF-HFP) composites.

PA-KNNT-P(VDF-HFP) composite films were synthesized using facile solution casting technique. Due to their wide range of applications in dielectric and electrical systems, phosphonic acid (PA)-modified tantalum-doped potassium sodium niobate (KNNT)-polyvinylidene fluoride co-hexafluoropropylene P(VDF-HFP) composite films have piqued the interest of academic researchers. Microstructural analysis showed that PA layers incorporated onto the KNNT particles within the polymer matrix. The PA-KNNT-P(VDF-HFP) composite exhibited improved dielectric and electrical performance over a broad range of frequency, and the value of the dielectric constant of the P(VDF-HFP) composites is improved by ≈119 over the P(VDF-HFP) matrix at a filler loading 19 wt.%. Moreover, PA-KNNT-P(VDF-HFP) composite also reveals higher dielectric constant (≈ 119) and AC conductivity than P(VDF-HFP)-KNNT composites, while maintaining suppressed dielectric loss ([Formula: see text] at 102Hz). It is also observed that the PA-KNNT-P(VDF-HFP) composite exhibited an insulator-conductor transition with a percolation threshold of fKNNT = 13.4 wt.%. As a result of their exceptional dielectric and electrical characteristics, PA-KNNT-P(VDF-HFP) composites have the potential to find exciting practical applications in a variety of electronic domains.

Characterization of UV Light Curable Piezoelectric 0-0-3 Composites Filled with Lead-Free Ceramics and Conductive Nanoparticles

Lead-free piezoelectric materials are essential for our healthy future but offer lower performance than lead-based materials. Different material combinations are explored to improve the performance of lead-free materials. By filling the UV light curable photopolymer resin with 30 vol.% lead-free piezoelectric ceramics and with up to 0.4 wt.% conductive nanofillers, thin and flexible piezoelectric 0-0-3 composites are formed. Two particle sizes of Potassium Sodium Niobate (KNN) and Barium Titanate (BTO) ceramics were used with four conductive nanofillers: Graphene Nanoplatelets (GNPs), Multi-Walled Carbon Nanotubes (MWCNTs), and two types of Graphene Oxide (GO). Resulting high viscosity suspensions are tape-cast in a mold as thin layers and subsequently exposing them to UV light, piezoelectric composite sensors are formed in 80 s. Even low nanofiller concentrations increase relative permittivities, however, they strongly reduce curing depth and increase undesirable dielectric losses. Non-homogeneous dispersion of nanofillers is observed. In total, 36 different compositions were mixed and characterized. Only six selected material compositions were investigated further by measuring mechanical, dielectric, and piezoelectric properties. Results show KNN composite performance as piezoelectric sensors is almost six times higher than BTO composite performance.

Hydrothermally prepared nano bricks of potassium sodium niobate for enhancing thermal and electrical properties of Poly(vinylidene fluoride)

This study presents the hydrothermal fabrication of K0.5Na0.5NbO3 nano bricks at a very lower temperature and its emphasis on the various properties of the polymer matrix. Even a smaller amount of such a nanostructured ceramic phase leaves a great influence on the various properties of the polymer matrix. Interestingly just a 10 % loading of KNN (potassium sodium niobate) nano bricks in a polymer matrix alters the remanant polarization to 6.10 μC cm−2 from 0.04 μC cm−2 for PVDF Poly(vinylidene fluoride) and 7.3 μC cm−2 at 20 % loading. The estimated dielectric at the frequency of 1 kHz shows more than 5 and 6 times increase at 10 % (εr = 13) and 20 % (εr = 15.4) of ceramic filler which is originally 2.5 for the pure PVDF matrix.

Growth and characterization of sodium potassium niobate single crystals near morphotropic phase boundaries

By using a high-temperature solution approach, lead-free single crystals of sodium potassium niobate Kx Na(1-x)NbO3 have been grown at three different phase boundary compositions (x = 0.17, 0.35, and 0.50). The monoclinic and orthorhombic crystal structures are present in the compositions × = 0.17 and × = 0.50 related crystal structures. Ferroelectricity is induced at lower temperatures and requires a smaller critical electric field when KNbO3 content is included into NaNbO3 crystals. Studies using the scanning electron microscope (SEM) and atomic force microscope (AFM) have shown how the sodium potassium niobate (KNN) crystals grow morphologically. With an increase in potassium concentration in the KNN system, the average step size falls. KNN crystals were subjected to impedance analyzer-based dielectric investigations. With an increase in concentration, a decrease in dielectric loss was found. The compositions with potassium concentrations of x = 0.50, 0.35, and 0.17 were found to have piezoelectric coefficients (d33) of 72 pC/N, 63 pC/N, and 52 pC/N, respectively.

Mechanical and electrical properties of sodium potassium niobate ceramic coating by plasma spraying

Potassium sodium niobate ceramics are environmentally friendly piezoelectric ceramics with excellent electrical properties. It is the most promising green piezoelectric ceramic for current applications. Currently, ceramics are needed in the form of thin films or coatings for brakes, sensors, etc. Most of the current ceramic films are prepared by physical vapor deposition and chemical vapor deposition. However, the ceramic layers prepared by the above methods are thin. The thickness of the ceramic layer has a large influence on its mechanical and electrical properties. The coatings prepared by thermal spraying are thicker, but there is no in-depth study about the relationship between the coating thickness and the mechanical and electrical properties of the coating. In this article, four different thicknesses of coatings were prepared by plasma spraying technology, and the relationship between the mechanical and electrical properties of the coatings and the thickness was studied and discussed. The results show that the coating microhardness and residual compressive stress values reach the maximum and the dielectric and ferroelectric properties are optimal when the coating thickness reaches 300 μm. The study of the connection between coating thickness and coating mechanical and electrical properties provides a theoretical study for the application of the coating in practice.

Structural and electrical properties of Zr-doped K0.48Na0.52NbO3 ceramics: “Hard” lead-free piezoelectric

The structural and electrical properties of K0.48Na0.52Nb1−xZrxO3−δ (x=0–0.04) ceramics prepared by the conventional solid-state reaction method were studied. Pellets with composition x≤0.03 sintered at 1125°C for 2h showed single-phase of potassium sodium niobate (KNN) perovskite structure. Based on X-ray diffraction and Raman results, a mixture of orthorhombic and monoclinic phases was observed in intermediate compositions. The addition of Zr improved the sinterability and the “hard” piezoelectric properties of KNN, increasing the Ec and Qm values. The composition with x=0.03 presented the highest permittivity at room temperature, ɛr′=363 and the lowest dielectric losses, tanδ=0.027. Moreover, it was the sample with the highest Qm and d33 values, with Qm=1781 and d33=82pC/N. It was therefore the best compositions to obtain a “hard” piezoelectric material based on Zr-doped KNN, which makes it promising candidate for use as “hard” lead-free piezoelectric material for high power applications.

Enhanced dielectric properties of gadolinium and vanadium co-substituted potassium sodium niobate (KNN)

Enhanced dielectric properties of gadolinium and vanadium co-substituted potassium sodium niobate (KNN)

Enhanced piezoelectricity and non-contact optical temperature sensing performance in Er3+ ion modified (K,Na)NbO3-based multifunctional ceramics

Rare earth ions doped ferroelectrics have attracted wide attentions due to their multifunction characteristics with both ferroelectric/piezoelectric properties and intriguing photoluminescence performance, which show great prospects for future multifunctional devices. In this work, a novel rare earth Er3+ ion modified potassium-sodium niobate (KNN) based ceramics were elaborately designed and prepared by the conventional solid-state reaction. The microstructure, phase structure, electric properties and photoluminescence performance of the Er3+ ion modified KNN-based ceramics were systematically investigated. Enhanced piezoelectricity (a considerable d33 of exceeding 300 pC/N and a large d33* up to 500 p.m./V) was realized through optimizing the substitution of BaZrO3 by (Er0.5,Na0.5)ZrO3. Both down-conversion and up-conversion photoluminescence emissions were detected in the optimal composition. The temperature-dependent upconversion emissions of the optimal Er3+ modified ceramic sample in the temperature range of 303–573K were verified to be applicable for non-contact optical temperature sensing with a maximum sensitivity Sa of 0.0028 K-1 and a peak relative sensitivity Sr of 0.96% K−1. Moreover, low-temperature sensing performance with a maximum Sr of 16.7% K−1 in the temperature range of 80–280K was also presented based on the temperature-dependent down-conversion emissions. With both decent electrical properties and intriguing photoluminescence performance, the Er3+-modified KNN-based ferroelectrics exhibit good application potential in the future multifunctional optoelectronic devices.

Enhanced piezoelectric properties for potassium sodium niobate lead-free piezoelectric ceramics prepared by microwave technology

Potassium-sodium niobate (Na, K)NbO3 (NKN) powder was synthesized at low temperature via microwave-assisted hydrothermal solovthermal method (MHSM). The resultant powder was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD results showed that pure (Na, K)NbO3 powder with a single perovskite structure was successfully synthesized when the concentration of mineralization exceeded 1 M. In order to reduce the volatilization of alkaline elements, NKN ceramics derived from 5M-powder were prepared in a microwave furnace. Microstructure, stoichiometry, and electrical properties of the obtained ceramics were investigated. The piezoelectric coefficient (d33), electromechanical coupling coefficient (kp) and remnant polarization (Pr) of the sample sintered at 1050 ℃ show optimal values of 132 pC/N, 38% and 26.3 µC/cm2, respectively. The results indicate that the microwave heating is a promising method for synthesizing and sintering NKN-based ceramics.