Potassium Niobate Research Articles

Synthesis of Ecofriendly Bimetallic Pt/Ni Nanoparticles on KNbO3 via Hydrothermal Process for Sustainable Hydrogen Evolution from NaBH4

The performance of nickel and platinum bimetallic nanoparticles (NPs) supported on potassium niobate (KNbO3) is evaluated in the catalytic hydrolysis of sodium borohydride (NaBH4) to generate hydrogen (H2). KNbO3 was synthesized via a hydrothermal route using Nb2O5 and KOH as precursors. X-ray diffraction (XRD) confirmed the crystalline orthorhombic structure of KNbO3. The Ni/Pt NPs, with an average size of 4.66 nm and a spherical morphology, were uniformly dispersed on the surface of KNbO3 nanosheets. The N2 physisorption isotherms of KNbO3 and Ni/Pt NPs were classified as type V with H3 hysteresis, showing specific surface areas of 0.170 and 2.87 m2 g−1, respectively. Catalytic performance studies examined various Ni/Pt molar ratios, with the 1:3 ratio (mol/mol) demonstrating the highest efficiency. Kinetic analysis of NaBH4 hydrolysis showed that the data fit the pseudo-first-order model. An increase in temperature enhanced the hydrogen generation rate (HGR), reaching 2068.3 mL gcat−1 min−1 at 315.05 K. The apparent activation energy (Ea) was determined to be 29.9 kJ mol−1. Durability assays showed only an 11% decrease in activity after 11 catalytic cycles. Thus, a promising, easy-to-synthesize, and environmentally friendly catalyst for NaBH4 hydrolysis has been developed.

Fabrication and in vitro biological properties of hydroxyapatite-sodium potassium niobate-barium titanate piezoelectric bioceramics

The utilization of piezoelectric materials in bone implants is appealing due to the inherent piezoelectric property of natural bone. The intrinsic electrical characteristics of piezoelectric biomaterials enhance antibacterial activities, biocompatibility, and bioactivity properties. This study delves into investigating the antibacterial properties, biocompatibility, and bioactivity of three-component biocomposites: sodium potassium niobate (KNN)-barium titanate (BT)-hydroxyapatite (HA). The combination of sodium potassium niobate and barium titanate, possessing suitable piezoelectric properties, with hydroxyapatite, known for its favorable biological properties, enhances the requisite properties for a bone implant. Among the various compositions studied, the combination comprising 70 wt% of the piezoelectric component (KNN-BT) and 30 wt% hydroxyapatite, labeled as 30HKB, emerged as the most optimal blend in terms of density, morphotropic phase boundary, and other biological tests conducted. Following polarization, the antibacterial efficacy of 30HKB against S. aureus bacteria cells increased by 61 %. Furthermore, the growth and adhesion of MC3T3-E1 osteoblast cells suggest enhanced biocompatibility of the 30HKB composite attributed to surface polarization. The surface charges generated by polarization facilitated the absorption of Ca2+ ions, as well as the interaction of HPO4 - and OH- ions with the precipitated Ca2+ ions, leading to the formation of the CaP layer. Hence, polarized piezoelectric ceramics exhibit heightened bioactivity compared to their non-polarized counterparts.

Visible Light Active 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3 Ferroelectric for Enhanced Photocatalytic Activity

AbstractThis study reports a visible light active Ba/Sc co‐doped potassium niobate (KNbO3) ferroelectric material for enhanced photocatalytic applications. Through 5% Ba and Sc co‐doping in KNbO3 (i.e., 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3), the electronic band gap (Eg) is narrowed down to the visible range of the solar spectrum. The prepared samples are systematically examined by using X‐ray diffraction and Raman spectroscopy, which confirms the successful incorporation of Ba and Sc ions into the KNbO3 lattice. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis reveal particle morphology and chemical homogeneity of prepared samples. The UV–vis spectroscopy and ferroelectric PE‐loop demonstrate enhanced optical absorption compared to host KNbO3 while retaining ferroelectric behavior. The photoelectrochemical (PEC) measurements under visible light irradiation demonstrate a notable enhancement in the photocurrent for 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3 (hereafter denoted by 5KBSNO) compared to undoped KNbO3. Additionally, the 5KBSNO sample displays enhanced RhB dye degradation efficiency, reaching ≈50% compared to parent KNbO3 (≈30%) under light irradiation. First‐principles density functional theory (DFT) calculations are employed to understand the mechanism responsible for the reduced band gap. This study presents a promising material for developing advanced ferroelectric photocatalysts with tailored band structures for efficient solar energy harvesting for energy conversion and contamination remediation applications.

Performance Analysis of Six Electro-Optical Crystals in a High-Bandwidth Traveling Wave Mach-Zehnder Light Modulator

In this study, a traveling wave Mach-Zehnder intensity modulator (TW-MZM) was designed and optimized for six different electro-optical (EO) crystals: lithium niobate (LNB), potassium niobate (KNB), lithium titanate (LTO), beta barium borate (BBO), cadmium telluride (CdTe), and indium phosphide (InP). The performance of each EO crystal, including optical and radio frequency (RF) loss, applied voltage, and modulation bandwidth, was estimated and compared. The results suggest that, in theory, KNB, LTO, BBO, and CdTe have the potential to outperform LNB. However, it should be noted that the loss associated with KNB and LTO is comparable to that of LNB. The findings demonstrated that BBO and CdTe exhibit a modulation bandwidth exceeding 100 GHz and demonstrate the lowest loss among the considered crystals based on the assumed geometry.

Improved bioactivity and corrosion resistance of NbO containing plasma electrolytic oxidation coating on ZM21 Mg alloy

ABSTRACT The present study reports the effect of niobium oxide (NbO) phase on the microstructure, corrosion, and bioactivity of coating on ZM21 Mg alloy by plasma electrolytic oxidation (PEO) process. NbO containing coatings are obtained by adding Potassium Niobate (KNbO3) along with the base electrolyte system, while the base electrolyte system consisted of sodium phosphate (Na3PO4⋅12 H2O) and potassium hydroxide (KOH). X-Ray Diffraction (XRD) was used for phase analysis, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) was employed to extract the microstructural features. Tafel curves were generated to study the corrosion behaviour, and bioactivity test was conducted in the simulated body fluid (SBF) for 14 days to study the bioactivity. XRD results revealed that the PEO coatings consisted of MgO phase, whereas the sample coated in the electrolyte containing KNbO3 showed NbO phase in addition to MgO phase. NbO containing coating showed higher corrosion resistance and excellent bioactivity.

Bioactive potassium and sodium niobate (K0.5Na0.5)NbO3 synthesized by solid‐state reaction and sol–gel methods

AbstractThis study proposes an innovative approach in the quest for piezoelectric materials, aiming to replace lead‐based ceramics (PZTs), known for their high toxicity. Potassium sodium niobate (KNN) compounds were chosen as a promising alternative. While the synthesis of KNN via solid‐state reaction (SSR) is common, maintaining the correct stoichiometry is challenging. In this work, we employed sol–gel (SG) and SSR methods for synthesis, combined with both conventional sintering techniques and spark plasma sintering. Comprehensive analyses were conducted, including crystal structure, microstructure, density, and piezoelectric properties, as well as bioactivity tests, among others. The results revealed that KNN samples exhibited remarkable piezoelectricity, coupled with surprising bioactivity, demonstrating good cell viability and resorption in a biological medium. Thoughtful selection of synthesis methods and variations in the sintering process were crucial in achieving high densification rates, enabling the investigation of the interplay between density and piezoelectric properties. Additionally, the application of polarization prior to immersion in a biological medium stimulated apatite precipitation. This indicates the promising application of these compounds as bioceramic devices.

Piezoelectrically induced augmented functionality of primary cultured hippocampal neurons on electrospun PVDF-(Na, K) NbO3 composite fibers

Owing to the risk of permanent disability of the associated tissue/organ, peripheral nerve injuries present one of the major concerns. As growth and regeneration of axons are sensitive towards electrical activity of substrate, polyvinylidene difluoride (PVDF)−10 vol% sodium potassium niobate (NKN) piezoelectric composite fibers were electrospun and corona poled at 17 kV. Electrospun PVDF-NKN fibrous scaffolds show remarkable increase in the average number of dendrites per neuron and mean soma area of primary cultured hippocampal neurons of embryonic mice which further increases after polarization (∼ 1.3 and 1.6 times of unpoled PVDF, respectively). The developed composite can be suggested as a potential candidate for peripheral nerve regeneration.

Lead-free KNNLT piezoceramic multilayer actuators with Ni electrodes cofired under low oxygen partial pressure

The fabrication of piezoelectric multilayer actuators (MLA) with lead-free piezoceramic materials and excellent performance represents a great challenge in the process of replacing the current family of lead-based actuators. Sintering under low pO2 allows co-firing with base metal electrodes, which is an important step towards competitive multilayer actuator fabrication technologies. We prepared sodium potassium niobate (KNNLT) piezoelectric multilayer actuators with Ni electrodes by sintering at low pO2 of 10−11 atm at 950 °C, followed by reoxidation at 850 °C in 10−6 atm. We demonstrate the impact of the sintering protocol, i.e., sintering temperature Ts and pO2, on the phase composition and continuity of Ni electrodes, and on the actuator performance. We discuss the subtle interplay between sintering conditions, microstructure, reoxidation kinetics and piezoelectric performance. The Ni-MLA exhibits a unipolar strain of 0.74 ‰ at 3 kV/mm, a normalized strain coefficient d33* = 247 p.m./V and a loss of tanδ = 0.041.

Enhancing pinning ability by the addition of potassium niobate nanorods in YBCO superconductor

In the current study, we have investigated the effect of adding potassium niobate (KNbO3) nanorods (NRs) in YBCO superconductor to improve flux pinning properties. The KNbO3-NRs are synthesized by hydrothermal method, and KNbO3-YBCO nanocomposites are prepared by incorporating variable amounts of the NRs in YBCO matrix by solid-state reaction method. X-ray diffraction (XRD) pattern confirmed the orthorhombic phase of YBCO, KNbO3-NRs, and KNbO3-YBCO nanocomposite samples. The morphology and composition of the YBCO, KNbO3, and KNbO3-YBCO nanocomposites are studied using field emission scanning electron microscopy (FESEM) and energy-dispersive x-ray spectroscopy (EDX). Magnetic measurements of KNbO3-YBCO nanocomposites are carried out at temperatures from 15 to 65 K under an external magnetic field from -7 to + 7 T. The value of critical temperature (TC0) in xKNbO3-YBCO nanocomposites showed no significant decrease from the TC0 value obtained for YBCO, indicating that inserting a modest amount of KNbO3-NRs into the YBCO matrix does not result in substantial changes in TC0. The critical current density (JC) showed an enhancement of ∼ 3.6 times in 0.5wt%KNbO3-YBCO nanocomposite compared to YBCO. Additionally, when the concentration of KNbO3-NRs in YBCO was raised, the critical current density (JC) decreased due to the accumulation of KNbO3-NRs at the interfaces between grain boundaries. The rate of JC decay decreases as the externally applied field increases for nanocomposite samples compared to YBCO, showing an improvement in the pinning properties of nanocomposites.

An ultrasound-activated heterojunction as ROS generator given scaffolds sonodynamic antibacterial effect

Potassium niobate (KNbO3) with favorable biocompatibility presented a great potential in the sonodynamic therapy of implant-related infection due to its superior piezoelectric performance. However, the rapid electron-hole pair recombination weakened its sonodynamic therapy effect. In this work, Au@KNbO3 heterojunctions were synthesized by depositing Au nanoparticles on KNbO3, and then mixed with poly-l-lactic acid (PLLA) powder to prepare scaffold by laser additive manufacturing. Herein, Au with lower Fermi level acted as electron trap to capture the ultrasonic-excited electrons from KNbO3. Subsequently, Au formed Schottky barrier with KNbO3 to prevent electrons backflow. As a result, the electron-hole was expected to be separated. EIS curves indicated that Au@KNbO3 presented a smaller arc radius than that of KNbO3, confirming the electron-hole separation efficiency of Au@KNbO3 was enhanced. Following that, ROS generation ability of the scaffold was significantly strengthened. Antibacterial tests revealed that the generated ROS could not only trigger protein leakage by disrupting bacterial cell membranes, but also deplete glutathione to weaken the antioxidant defense of bacteria. As a consequence, the scaffold exhibited excellent antibacterial abilities of 92% and 90% against S. aureus and E. coli, respectively. Collectively, this work provided a promising countermeasure to fight the implant-related infection.

Using KNbO3 catalyst produced from a simple solid-state synthesis method in a new piezophotocatalytic ozonation hybrid process

The present work reports the development and application of potassium niobate (KNbO3) as a catalyst in a novel hybrid piezophotocatalytic ozonation process aimed at wastewater remediation. Pure KNbO3 samples were produced through a simple solid-state synthesis using water-soluble ammonium niobate (V) oxalate hydrate (C4H4NNbO9·xH2O) as niobium source, employing different potassium precursors (KNO3, K2CO3, KOH, and C8H5KO4). The synthesis was also carried out using powdered niobium oxide as a precursor, aiming to evaluate the differences between the niobates obtained. The results achieved in this study show that all the niobates produced using ammonium niobate (V) oxalate hydrate were composed solely of the orthorhombic structure of KNbO3, while the materials synthesized using niobium oxide exhibited the rhombohedral structure of KNbO3 along with niobium-rich potassium niobates (K3Nb8O21, K2Nb4O21, and KNb3O8) and residual niobium oxide. This behavior was attributed to the enhanced chemical homogeneity derived from the synthesis using ammonium niobate (V) oxalate hydrate, which facilitated the reaction between the components during the thermal treatment step. Furthermore, the optical and morphological properties of the niobates were considerably influenced by the application of different potassium salts. Owing largely to its morphological and electrical properties, the material synthesized using potassium hydrogen phthalate displayed the highest photocatalytic activity in terms of methylene blue discoloration among the niobates produced using C4H4NNbO9·xH2O. Finally, the proposed piezophotocatalytic ozonation process was found to be a highly efficient strategy for the discoloration of methylene blue, as it successfully harnessed the synergy between the multiple mechanisms involving active radical generation toward the development of a highly promising hybrid advanced oxidation process.

Laser‐induced Fano interference subsumed by electron–phonon coupling in orthorhombic KNbO3nano‐bricks: An ab initio vibrational and Raman spectroscopic investigation

AbstractHydrothermally prepared potassium niobate (KNbO3) nanoparticles are characterized meticulously to explore various crystallographic, microstructural, morphological, optical, compositional, and lattice‐vibrational properties. Laser power‐dependent Raman spectroscopy is employed to study the Fano effect in asymmetrically broadened optic (LO/TO) phonon modes in the orthorhombic KNbO3system, considering interference with the interband electronic continuum. The phonon softening, alterations in charge‐phonon coupling constant, linewidth and lifetime of phonon modes, and so on are explained in the light of theories formulated by Fano, Allen, and Hui, accompanying factor group analysis of the Raman‐active modes. Under local heating via focused laser irradiation, highly sensitive Raman spectra introspect perturbations in the generic vibrations at the first Brillouin zone center and moderations in the constructive/destructive interference conditions of resonant Fano scattering. Density functional theory (DFT)‐based calculations on phonon dispersion, density of phonon states, and relevant thermodynamic attributes decipher the theoretical background. Amid photoexcited electron plasma, the charge‐phonon coupling for distinct modes is strengthened considerably against strong excitation intensity without any unwanted anharmonicity, extensive lattice thermal expansion, phonon decay, or microscopic phase transformation. Finally, the direction of asymmetry, particle–particle, and particle–quasiparticle interactions are illustrated using Feynman diagrams for the associated and phonon modes.

Graphene surface plasmon sensor for ultra-low-level SARS-CoV-2 detection.

Precisely detecting the ultra-low-level severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial. The detection mechanism must be sensitive, low-cost, portable, fast, and easy to operate to tackle coronavirus disease 19 (COVID-19). This work proposes a sensor exploiting graphene surface plasmon resonance to detect SARS-CoV-2. The graphene layer functionalized with angiotensin-converting enzyme 2 (ACE2) antibodies will help efficient adsorption of the SARS-CoV-2. In addition to the graphene layer, ultra-thin layers of novel two-dimensional materials tungsten disulfide (WS2), potassium niobate (KNbO3), and black phosphorus (BP) or blue phosphorus (BlueP) used in the proposed sensor will increase the light absorption to detect an ultra-low SARS-CoV-2 concentration. The analysis presented in this work shows that the proposed sensor will detect SARS-CoV-2 as small as ∼1 fM. The proposed sensor also offers a minimum sensitivity of 201 degrees/RIU, a figure-of-merit of 140 RIU-1, and enhanced binding kinetics of the SARS-CoV-2 to the sensor surface.

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.

Low-temperature processing of screen-printed piezoelectric KNbO3 with integration onto biodegradable paper substrates

The development of fully solution-processed, biodegradable piezoelectrics is a critical step in the development of green electronics towards the worldwide reduction of harmful electronic waste. However, recent printing processes for piezoelectrics are hindered by the high sintering temperatures required for conventional perovskite fabrication techniques. Thus, a process was developed to manufacture lead-free printed piezoelectric devices at low temperatures to enable integration with eco-friendly substrates and electrodes. A printable ink was developed for screen printing potassium niobate (KNbO3) piezoelectric layers in microns of thickness at a maximum processing temperature of 120 °C with high reproducibility. Characteristic parallel plate capacitor and cantilever devices were designed and manufactured to assess the quality of this ink and evaluate its physical, dielectric, and piezoelectric characteristics; including a comparison of behaviour between conventional silicon and biodegradable paper substrates. The printed layers were 10.7–11.2 μm thick, with acceptable surface roughness values in the range of 0.4–1.1 μm. The relative permittivity of the piezoelectric layer was 29.3. The poling parameters were optimised for the piezoelectric response, with an average longitudinal piezoelectric coefficient for samples printed on paper substrates measured as d33, eff, paper = 13.57 ± 2.84 pC/N; the largest measured value was 18.37 pC/N on paper substrates. This approach to printable biodegradable piezoelectrics opens the way forward for fully solution-processed green piezoelectric devices.

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.

Synthesis of perovskite-type potassium niobate using deep eutectic solvents: A promising electrode material for detection of bisphenol A

This study demonstrates a hydrothermal method to prepare perovskite-type potassium niobate (KNbO3) through deep eutectic solvent (DES), which is further used as an electrode material for the determination of bisphenol A (BPA). The as-synthesized KNbO3 was systematically characterized by different microscopic and spectroscopic techniques. The KNbO3-modified electrode demonstrates excellent electrocatalytic activity for BPA compared to the pristine electrode. The enhanced performance of the proposed sensor is attributed to the numerous active sites, large electrochemical surface area, high electrical conductivity, and rapid electron transfer. The fabricated sensor shows a wide detection range (0.01–84.3 μM), a low limit of detection (0.003 μM), a high sensitivity (0.51 μA μM−1 cm−2), and good anti-interference abilities towards the BPA detection by linear sweep voltammetry method. Besides, it was successfully applied to determining BPA in food samples, demonstrating good practicability. This design paves a new way to fabricate efficient electrode material for various electrochemical applications using a DES medium.

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.

Investigation of electro-optical properties of gradient potassium niobate

The gradient perovskite material of potassium niobate is investigated in this work. As a result of the research, a gradient change in the properties was found: transformations of the IR absorption spectrum, the magnitude of the half-wave voltage depending on the composition of the grown potassium niobate crystal. The value of the half-wave voltage for plates cut from crystalline potassium niobate varied from 1500 to 1700 V with a change in the composition of potassium niobate in the range KxNb2-xO5-2x at x=0.9..1.

Synthesis of niobium(iv) carbide nanoparticles via an alkali-molten-method at a spatially-limited surface of mesoporous carbon.

One-pot synthesis of niobium carbabide (NbC) nanoparticles with ca. 30-50 nm was achieved via a rationally designed novel alkali-molten salt method using niobium oxide (Nb2O5), potassium carbonate (K2CO3), and mesoporous carbon (MPC). In this reaction, potassium niobate (KNbO3) was produced as an intermediate and carbonization of KNbO3 proceeds at a spatially limited external surface encompassed by the mesopores of MPC due to the repulsive characteristics of ionic KNbO3 toward hydrophobic MPC, which affords the size-controlled NbC nanoparticles with a narrow particle distribution. The particle sizes tended to become smaller as the pore sizes of MPCs or the temperature on the calcination under the nitrogen stream decreased. Elemental reactions along the one-pot synthesis of NbC nanoparticles were clarified by X-ray spectroscopic, thermogravimetric, and mass spectrometric measurements.