Potassium Niobate Research Articles

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.

KNbO3 photoelectrode for DSSC: a structural, optical and electrical approach.

In this work, we present the potassium niobate (KNbO3) nanoparticles as a suitable mesoporous photoelectrode for dye-sensitized solar cells (DSSCs). The KNbO3 particles were synthesized by the microwave-assisted hydrothermal method using mild conditions and characterized by SEM, XRD, Raman, and UV-Vis diffuse reflectance. The particles presented a pyramidal tower-like shape with an orthorhombic structure and an indirect bandgap of (3.0 ± 0.1) eV. Dye-sensitized solar cells were assembled using the synthesized KNbO3 nanoparticles, which were deposited as a photoelectrode on a TiO2 recombination charge blocking layer. It is noticeable that the synergistic operation of the TiO2 blocking layer and KNbO3 photoelectrode is essential to achieve photovoltaic behaviour in our solar cells. The short-circuit current density of Jsc = 2.82 mA, open-circuit voltage Voc = 669 mV, fill factor FF = 0.62, and a power conversion efficiency PCE = 1.17%, reports elevated parameters if compared to other DSSCs alternative materials, becoming potassium niobate suitable as photoelectrode.

Enhanced photocatalytic hydrogen generation over a Z-scheme nanohybrid composed of porphyrin cobalt metal-organic frameworks in-situ fabricated on potassium niobate microflowers

A promising direct Z-scheme KNO MF/Co-PMOF nanohybrid was facilely achieved by cobalt meso-tetrakis(4-carboxyphenyl) porphyrin metal organic frameworks (Co-PMOF) in-situ grown on potassium niobate microflowers (KNO MF). The tight combination of the two semiconductors can be confirmed by HRTEM. It was found that the spectral range can be effectively expanded, and also the carrier separation and migration efficiency in the nanohybrid can be effectively improved by the establishment of the built-in electric field at the interface. Under irradiation without adding any cocatalysts, the optimized KNO MF/Co-PMOF exhibited 14.5 times higher activity than that of pristine KNO MF. Moreover, the KNO MF/Co-PMOF showed a good durability in five continuous recycles (30 h). This study will provide a promising strategy for designing Z-type photocatalysts for enhanced H2 release.

Effect of Mn Doping on the Microstructure and Electrical Properties of Potassium Niobate Ceramics Using Plasma Spraying

KNN piezoelectric ceramics are of great importance in the field of scientific research due to their high Curie temperature, good electrical properties, etc. The application of potassium sodium niobate K0.5Na0.5NbO3 (KNN) is strictly limited due to the volatility of Na+ and K+ in KNN and its leakage current. In order to investigate the effect of Mn doping on KNN-based piezoelectric ceramic coatings, KNN and KNN-0.02Mn (KNMN) coatings were successfully prepared using a plasma spraying technique. The phase structure, microscopic morphology, and electrical properties of the coatings were studied in the research. The results showed that both the KNN and KNMN coatings had chalcogenide structures. The KNN coating had an orthogonal phase structure, whereas the KNMN coating had a tetragonal phase structure. Compared with the KNN coating, the microhardness of the KNMN coating was improved through doping with Mn ions. The doping of Mn ions could replace both the A and B sites in the KNN piezoelectric ceramics, further reducing the oxygen vacancies and leakage currents in the coating, and its dielectric properties were improved.

Erratum: “Resistance degradation in sputtered sodium potassium niobate thin films and its relationship to point defects” [Appl. Phys. Lett. 121, 162902 (2022)

Erratum: “Resistance degradation in sputtered sodium potassium niobate thin films and its relationship to point defects” [Appl. Phys. Lett. <b>121</b>, 162902 (2022)

Resistance degradation in sputtered sodium potassium niobate thin films and its relationship to point defects

The reliability of piezoelectric thin films is crucial for piezoelectric micro-electromechanical system applications. The understanding of resistance degradation in piezoelectric thin films requires knowledge about point defects. Here, we show the resistance degradation mechanism in the lead-free alternative sodium potassium niobate (KNN) thin films and the relationship to point defects in both field-up and field-down polarities. The conduction mechanism of KNN thin films is found to be Schottky-limited. Furthermore, a reduction in Schottky barrier height accompanies the resistance degradation resulting from interfacial accumulation of additional charged defects. We use thermally stimulated depolarization current measurements and charge-based deep level transient spectroscopy to characterize the defects in KNN thin films. Our results show that oxygen vacancies accumulate at the interface in field-up polarity, and multiple defects accumulate in field-down polarity, potentially oxygen vacancies and holes trapped by potassium vacancies. We use wafer deposition variation to create samples with different film properties. Measurement results from these samples correlate resistance degradation with the defect concentration. We find the natural logarithm of leakage current to be linearly proportional to the defect concentration to the power of 0.25. The demonstrated analysis provides a precise and meaningful process assessment for optimizing KNN thin films.

An in vivo toxicity assessment of piezoelectric sodium potassium niobate [NaxK1-xNbO3 (x=0.2-0.8)] nanoparticulates towards bone tissue engineering approach.

One of the recent challenges in the design/development of prosthetic orthopedic implants is to address the concern of local/systemic toxicity of debris particles, released due to wear or degradation. Such debris particles often lead to inflammation at the implanted site or aseptic loosening of the prosthesis which results in failure of the implant during long run. Several in vitro studies demonstrated the potentiality of piezoelectric sodium potassium niobate [NaxK1-xNbO3 (x=0.2, 0.5, 0.8), NKN] as an emerging next-generation polarizable orthopedic implant. In this perspective, we performed an in vivo study to examine the local and systemic toxicity of NKN nanoparticulates, as a first report. In the present study, male Wistar rats were intra-articularly injected to the knee joint with 100μl of NKN nanoparticulates (25mg/ml in normal saline). After 7days of exposure, the histopathological analyses demonstrate the absence of any inflammation or dissemination of nanoparticulates in vital organs such as heart, liver, kidney and spleen. The anti-inflammatory cytokines (IL-4 and IL-10) profile analyses suggest the increased anti-inflammatory response in the treated rats as compared to non-injected (control) rats, preferably for the sodium and potassium rich NKN i.e., Na0.8K0.2NbO3 and Na0.2K0.8NbO3. The biochemical analyses revealed no pathological changes in the liver and kidney of particulate treated rats. The present study is the first proof to confirm the non-toxic nature of NKN nanoparticulates which provides a step forward towards the development of prosthetic orthopedic implants using biocompatible piezoelectric NKN ceramics.

Interplay of surface polarization charge, dynamic electrical stimulation and compositional modification towards accelerated osteogenic response of NaxK1-xNbO3 piezo-bioceramics

Bone remodeling processes involve endogenous bioelectrical signals such as piezoelectric charges. Moreover, external electrical stimulation helps in improving the healing capability of injured tissues by modulating the metabolic signaling pathways of cells. Towards this end, the present study reveals the influence of the combined action of electrostatic surface polarization charge and dynamic pulsed electrical stimulation alongwith compositional modification towards improving the osteogenic response of emerging piezo-bioceramics, sodium potassium niobate [NaxK1-xNbO3 (x=0.2-0.8), NKN]. The dependence of crystal structure on compositions (x) was retrieved by Rietveld refinement and X-ray peak profile analyses. The surface charge, stored in the polarized (@ 25kV at 500°C) NaxK1-xNbO3 (x=0.2, 0.5, 0.8) samples were measured to be 0.52, 0.50 and 0.47μC/cm2, respectively, using thermally stimulated depolarized current (TSDC). X-ray photoelectron spectroscopy (XPS) survey scan spectra revealed that the polarization process does not alter the surface chemistry of NKN. Negatively charged surfaces are observed to accelerate early-stage adhesion of osteoblast-like cells which further results in enhanced spreading of adhered cells. Subsequently, the dynamic pulsed electrical stimulation of 1V/cm with the pulse duration of 400μs was applied, while the cells were being adhered on electrostatically charged surfaces. The quantitative and qualitative analyses revealed that the synergistic action of electrostatic surface polarization charge and dynamic pulsed electrical stimulation further accelerates cell proliferation and differentiation on negatively charged surfaces of Na and K-rich compositions of NKN. The mechanism of augmented cellular activity was analyzed using intracellular Ca2+ measurement.

Enhanced photocatalytic performance by polarizing ferroelectric KNbO3 for degradation of plastic wastes under mild conditions

Although photocatalysts can convert plastic wastes into energy fuels and show unique advantages in the treatment of plastic wastes, photocatalytic efficiency is still limited by the fast recombination of photoexcited charges. In this paper, potassium niobate (KNbO3) nanosheet with the ferroelectric property was synthesized and polarized under an external electric field. Polarization does not change the morphology and structure of KNbO3, but effectively enhances the spontaneous polarization field. This spontaneous polarization field exists through the whole material and can effectively improve the separation of photogenerated charges. The photocatalytic efficiency of polarized KNbO3 (P-KNbO3) for degradation of PE and PP improves by about 210 % and 140 %, compared with KNbO3. P-KNbO3 also shows excellent photocatalytic activity for the degradation of real-world waste plastic products (plastic bags, gloves, tubes and boxes). This study might provide insights into designing high-efficiency photocatalysts for plastic waste treatment by regulating and controlling the polarization of ferroelectric materials.

In Vitro Molecular Study of Titanium-Niobium Alloy Biocompatibility.

Titanium dental implants have common clinical applications due to their biocompatibility, biophysical and biochemical characteristics. Although current titanium is thought to be safe and beneficial for patients, there are several indications that it may release toxic metal ions or metal nanoparticles from its alloys into the surrounding environment, which could lead to clinically relevant complications including toxic reactions as well as immune dysfunctions. Hence, an adequate selection and testing of medical biomaterial with outstanding properties are warranted. This study was designed to explore the biocompatibility of smooth titanium-niobium alloy (S_TiNb) versus smooth titanium commercially pure (S_TiCp)—a reference in implantology. All experiments were performed in vitro using human osteoblast-like SaOs-2 and monocyte THP-1 cell lines as models. Cell adhesion and growth morphology were determined by scanning electron microscopy, while cell viability was evaluated using WST-1 assay. Because niobate anions or niobium nanoparticles can be released from implants during biomaterial-cell interaction, potential immunotoxicity of potassium niobate (KNbO3) salt was evaluated by examining both metabolic activity and transcriptomic profiling of treated THP-1 monocytes. The main findings of this study are that S_TiCp and S_TiNb discs do not show an impact on the proliferation and viability of SaOs-2 cells compared to polystyrene surfaces, whereas a significant decrease in THP-1 cells’ viability and metabolic activity was observed in the presence of S_TiNb discs compared to the control group. However, no significant changes were found neither at the metabolic activity nor at the transcriptomic level of THP-1 monocytes exposed to KNbO3 salt, suggesting that niobium has no effect on the immune system. Overall, these data imply a possible toxicity of S_TiNb discs toward THP-1 cells, which may not be directly related to niobium but perhaps to the manufacturing process of titanium-niobium alloy. Thus, this limitation must be overcome to make titanium alloy an excellent material for medical applications.

Electromechanical properties of paper‐derived potassium sodium niobate piezoelectric ceramics

AbstractThe small‐signal dielectric and piezoelectric coefficients of paper‐derived sodium potassium niobate, K0.5Na0.5NbO3 (KNN), were compared with those of conventionally prepared samples. Results show similar functional properties of paper‐derived KNN without significantly decreasing the small‐signal piezoelectric coefficient. The structure and microstructure analysis of conventional KNN and paper‐derived KNN did not reveal any significant difference in the crystal structure and grain size. However, the temperature‐dependent inter‐ferroelectric phase transition temperature estimated from the temperature‐dependent dielectric permittivity data revealed a decrease of approximately 18°C for the paper‐derived KNN and is possibly associated with the structural and microstructural defects. This work indicates that optimizing suspension chemistry and sintering conditions will be critical to enhance the functional response of paper‐derived KNN further. Moreover, paper‐derived ceramic processing, a novel and cost‐effective additive manufacturing technology, can be potentially used to fabricate other electroceramics with a wide range of porosities and sizes as well as complex geometries and multilayer structures.

Microstructure and Intrinsic Strain of Nanocrystals in Ferroelectric (Na,K)NbO3 Nanofibers.

Densely woven highly crystallized biocompatible sodium–potassium niobate Na0.35K0.65NbO3 fibers with an average diameter of 100–200 nm and several hundreds of microns in length were sintered by the sol–gel calcination-assisted electrospinning technique. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) confirmed preferential cube-on-cube [001] orientation of nanocrystals within the fiber’s body, separated by a low angle grain boundary. The Williamson–Hall method was employed to analyze the broadening of XRD reflections and to accurately determine the size and intrinsic strain of nanocrystal fiber aggregates. The main objective of this article is to test the potential capacity of direct XRD analysis to noninvasively control crystallite size and lattice distortion in core-shell coaxial nanofibers.

Investigation of magnetic properties and converse magnetoelectric effect in the composite of doped barium hexaferrite with potassium niobate, 0.5BaFe10Sc2O19-0.5KNbO3 and 0.5BaFe10In2O19-0.5KNbO3

This study investigates the magnetic and electric properties of the 0.5BaFe 10 Sc 2 O 19 -0.5KNbO 3 (0.5BFSc2O-0.5KNO) and 0.5BaFe 10 In 2 O 19 -0.5KNbO 3 (0.5BFIn2O-0.5KNO) composite samples. Refined X-ray diffraction (XRD) studies substantiate the presence of both ferrimagnetic (BFSc2O and BFIn2O) and ferroelectric KNbO 3 phase with the ratio (0.5:0.5) in both the compounds without any impure phase. By electric poling the samples with an electric field of 2.5 kV/cm, magnetization shows a different behaviour (decreasing in Sc and increasing in doped composite), can be attributed to the electric field induced changes of spin states due to stress induced at the interface of ferrimagnetic (FM)/ferroelectric (FE) regions. Strong converse magnetoelectric coupling (CME) was observed in both the compounds, with a large electric field modulation in magnetism (80%) in the 0.5BFInO-0.5KNO composite. Dielectric studies reveal the presence of ferroelectric ( FE-T c ) transition around the magnetic Curie temperature ( FM-T c ) of respective composites, further indicates the presence of converse magnetoelectric coupling in both systems. • Magnetic and magnetoelectric properties of the composite of doped barium hexaferrite with potassium niobate are studied. • Refined XRD show both ferroelectric KNbO3 and ferrimagnetic BaFe10Sc2O19 and BaFe10In2O19 phases present with a 50:50 ratio. • DC magnetization shows different doping element in the ferrites leads to different magnetic behaviour after electric poling. • Converse magnetoelectric coupling of 45% in 0.5BaFe10Sc2O19-0.5KNbO3 and 80% in 0.5BaFe10In2O19-0.5KNbO3 was observed. • Dielectric studies show the ferroelectric transition around their respective magnetic Curie temperature in both the systems.

Analytical study of the ferroelectric properties of Fe-doped KNbO3 single crystal

We report herein the structural, dielectric, ferroelectric, and domain properties of an Fe-doped potassium niobate ([KNbO3] KNb1-xFexO3; x = 0.01 mol%) single crystal synthesized by a flux method. X-ray diffraction (XRD) results illustrate that the given sample adopts orthorhombic crystal symmetry with the space group Amm2. On submitting the sample to differential thermal analysis (DTA), two endothermic peaks were observed, the first at 224 °C and the second at 425 °C. Dielectric studies with respect to temperature from 30 to 500 °C showed that the Curie temperature (Tc) of the Fe-doped KNbO3 single crystal occurred at 435 °C. The measured dielectric loss of the crystal is in good agreement with other dielectric studies. The relationship between polarization and electric field (PE) shows that the spontaneous polarization (Ps) and coercive field (Vc) for the doped material are lower than those for an undoped KNbO3 single crystal, indicating a weakly ferroelectric nature of the sample. A trinocular microscope has been used to study the domain properties and revealed the formation of 60° and 90° domain walls. Furthermore, upon etching the single crystal with nitric acid (HNO3), etch pits and a twinning plane of the domains were formed. Finally, electric fields of 100, 500, and 1000 V/cm were applied to the Fe-doped KNbO3 single crystal surface, whereupon the nucleation and dissipation of new domains could be observed.

2D–2D lattice engineering route for intimately coupled nanohybrids of layered double hydroxide and potassium hexaniobate: Chemiresistive SO2 sensor

2D–2D lattice engineering route is used to synthesize intimately coupled nanohybrids of layered double hydroxide (LDH) and potassium hexaniobate. The 2D–2D lattice engineering route is based on the electrostatically derived self-assembly of delaminated zinc-chromium-layered double hydroxide (ZC-LDH) nanosheets and potassium hexaniobate (HNb) nanosheets (ZCNb nanohybrids). The 2D–2D lattice-engineered ZCNb nanohybrids display expanded surface area, mesoporous anchored nanosheets network morphology, and intimate coupling between nanosheets. The 2D–2D lattice engineered ZCNb nanohybrids are used for the low temperature operated gas sensor. The ZCNb nanohybrids display outstanding selectivity for the SO2, with the high response of 61.5% compared to pristine ZC-LDH (28.08%) and potassium niobate (8%) at 150 °C. Moreover, ZCNb sensors demonstrate superior response and recovery periods of 6 and 167 s at 150 °C, respectively. This result underscores the exceptional functionality of the ZCNb nanohybrids as efficient SO2 sensors. Moreover, these findings vividly demonstrate that the 2D–2D lattice-engineered ZCNb nanohybrids are quite effective not only in improving the gas sensor activity but also in developing of new type of intimately coupled mesoporous LDH-metal-oxide based hybrid materials.

Using Feature-Assisted Machine Learning Algorithms to Boost Polarity in Lead-Free Multicomponent Niobate Alloys for High-Performance Ferroelectrics.

To expand the unchartered materials space of lead‐free ferroelectrics for smart digital technologies, tuning their compositional complexity via multicomponent alloying allows access to enhanced polar properties. The role of isovalent A‐site in binary potassium niobate alloys, (K,A)NbO3 using first‐principles calculations is investigated. Specifically, various alloy compositions of (K,A)NbO3 are considered and their mixing thermodynamics and associated polar properties are examined. To establish structure‐property design rules for high‐performance ferroelectrics, the sure independence screening sparsifying operator (SISSO) method is employed to extract key features to explain the A‐site driven polarization in (K,A)NbO3. Using a new metric of agreement via feature‐assisted regression and classification, the SISSO model is further extended to predict A‐site driven polarization in multicomponent systems as a function of alloy composition, reducing the prediction errors to less than 1%. With the machine learning model outlined in this work, a polarity‐composition map is established to aid the development of new multicomponent lead‐free polar oxides which can offer up to 25% boosting in A‐site driven polarization and achieving more than 150% of the total polarization in pristine KNbO3. This study offers a design‐based rational route to develop lead‐free multicomponent ferroelectric oxides for niche information technologies.

Total-internal-reflection-based optical rotation quasi-phase-matching technique realized in a biaxial electro-optic chiral material to generate highly efficient second harmonic

This work demonstrates a total-internal-reflection-based optical rotation quasi-phase-matching technique availing polarization rotation under the influence of an external electric field in a rectangular-shaped potassium niobate crystal coated with a thin layer of gallium phosphide. This thin film is utilized to regulate the phase shifts caused by the propagation of p - and s -polarized light at the slab-film interface at each total internal reflection bounce point. The peak conversion efficiency of 3.3%/W/cm, obtained from the computer-aided simulation, reflects the combined field effect of optical rotation quasi-phase-matching and fractional quasi-phase-matching techniques. The effect of optical losses and the nonlinear law of reflection have also been included to simulate the generation of a second-harmonic wavelength of 2150 nm.

Effects of transition metal dopants on the electronic structure of potassium niobate

Potassium niobate (KNbO3) is an important ferroelectric and photorefractive material that finds multiple nonlinear optical and photorefractive applications such as two-beam coupling and dynamic holography. We employ standard Density Functional Theory to examine two defect complexes in KNbO3 doped with 3-d transition metals. These defect complexes involve the substitution of a Nb with a 3-d transition metal element and (1) a coordinating oxygen vacancy induced in the nearest-neighbor oxygen shell or (2) a non-coordinating oxygen vacancy induced in the supercell as far away as possible from substitution impurity. With the exception of Ti and V, the 3-d transition metal dopants studied here may represent viable dopants for purposes of extending the photorefractive spectral response of KNbO3. Our results indicate that each of these complexes introduces defect states into the gap of KNbO3. Furthermore, we notice that the distribution of impurity states changes quite systematically across the 3-d transition metal row, and we note the effects of the disruption of the crystal field in the case of the coordinating O vacancy on the position and ordering of defect states within the gap. Substituting KNbO3 with transition metal ions can, therefore, significantly affect its optical and infrared properties, exemplifying how a detailed understanding of the electronic structure can be an important tool in tailoring the properties of this material for ferroelectric and photorefractive applications.

Evaluation of the structural and electrical properties of perovskite NKN-LN ceramics for energy storage applications

A way to prepare a family of lead-free piezoelectric perovskite sodium potassium niobate–lithium niobate ceramics using a solid-state reaction technique is described.