NbO3 Materials Research Articles

Synthesis of lead-free piezoelectric potassium sodium niobates for the preparation of anti-fouling KNN porous membrane

Potassium sodium niobates (KNNs) have garnered significant attention owing to their lead-free nature and potential for use in self-cleaning membranes. This paper presents the synthesis of (K0.5Na0.5)NbO3 materials for the fabrication of porous membranes, which enable in situ ultrasonic resonance to effectively eliminate contaminants from the membrane surface. KNN powder was synthesized via solid-state reactions, and the membranes were prepared using conventional sintering techniques. The effects of ball-milling time and calcination temperature on the phase structure, pore size, permeance, flexural strength, chemical stability, and piezoelectric properties were comprehensively investigated. The optimal membranes exhibited an average pore size of approximately 300 nm, a porosity of 23 %, and permeance of 220 L m−2 h−1 bar−1 at a sintering temperature of 1050 °C. A polarized electrical field with a strength of 1 kV/mm was applied to the membranes, resulting in an ultrasonic response of 20 mV at an excitation voltage of 20 V with a frequency of 200 kHz. Furthermore, the in situ anti-fouling performance was evaluated by conducting filtration tests on a 500 ppm oil-in-water (O/W) emulsion, demonstrating that the stationary flux increased by 46.7 % when subjected to an excitation voltage of 60 V.

Improved strain and transduction values of low-temperature sintered CuO-doped PZT-PZNN soft piezoelectric materials for energy harvester applications

In this study the low-temperature sintering effects and improved piezoelectric properties of CuO-doped 0.69 Pb(Zr0.47Ti0.53)O3-0.31[Pb(Zn0.4Ni0.6)1/3Nb2/3]O3 ceramics were investigated. At high temperatures, a sintered Pb(Zr,Ti)O3–Pb(Zn,Ni)NbO3 material has excellent piezoelectric properties such as a high piezoelectric charge coefficient (d33), high electromechanical coupling coefficient (kp), and high relative dielectric permittivity (εr). However, low-temperature sintering of functional ceramics is important for industrial device applications. For sensor applications, sintering or fabrication temperature is important because processing temperatures can interfere with process and material compatibility. Therefore, in this study, low-temperature sintering effects were investigated by employing low-temperature sintering aids while maintaining the piezoelectric properties. CuO was selected as the sintering aid for these applications. We will investigate and discuss the effects of the low-temperature sintering aid of CuO on the Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material in device applications. By employing the CuO dopant to Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material, the strain and transduction values were increased while reducing the sintering temperature.

Lead-free (Ag,K)NbO3 materials for high-performance explosive energy conversion.

Explosive energy conversion materials with extremely rapid response times have broad and growing applications in energy, medical, defense, and mining areas. Research into the underlying mechanisms and the search for new candidate materials in this field are so limited that environment-unfriendly Pb(Zr,Ti)O3 still dominates after half a century. Here, we report the discovery of a previously undiscovered, lead-free (Ag0.935K0.065)NbO3 material, which possesses a record-high energy storage density of 5.401 J/g, enabling a pulse current ~ 22 A within 1.8 microseconds. It also exhibits excellent temperature stability up to 150°C. Various in situ experimental and theoretical investigations reveal the mechanism underlying this explosive energy conversion can be attributed to a pressure-induced octahedral tilt change from a - a - c + to a - a - c -/a - a - c +, in accordance with an irreversible pressure-driven ferroelectric-antiferroelectric phase transition. This work provides a high performance alternative to Pb(Zr,Ti)O3 and also guidance for the further development of new materials and devices for explosive energy conversion.

Substantial improvement on electrical energy harvesting by chemically modified/sandpaper-based surface modification in micro-scale for hybrid nanogenerators

Herein, a unique energy harvester made of triboelectric and piezoelectric effects made of a dual perovskite solid system by substituting a trace amount of perovskite BaTiO3 into the parent material K0.5Na0.5NbO3 material. The combined system (1 − x) K0.5Na0.5NbO3- x BaTiO3 at x = 0, 0.02, 0.04, 0.06 and 0.08 is lead-free and eco-friendly in nature. The doping concentration KNN- 0.02 BTO shows high remnant polarization and electrical response. The active layer of the hybrid device is made of mixing KNN- 0.02 BTO into the PDMS matrix. The electrical response of the composite film is studied systematically with the addition of various weight percentages of nanoparticles into the PDMS matrix, where 10 wt% shows the high electrical output. The electrical responses with respect to surface roughness have been studied, and the roughness has been created using cost-effective soft lithographic techniques. The individual components, such as TENG and PENG, in comparison with the hybrid device, had been systematically studied, and the hybrid performance is high compared to individual components. The PCF-NG device generates a maximum electrical output of ≈610 V/13.7 μA with a power density of 0.55 W/m2 at load resistance of 100 MΩ. Further, the device demonstrates capability in powering low power electronic devices such as capacitor charging, LED lit up, and powering wristwatches. This work would provide an opportunity for developing a stable and highly reliable built-in power source for various applications and would lead a path towards battery-free smart electronics.

Optical temperature sensing and luminescent switching properties in Pr/Er‐doped (K0.5Na0.5)NbO3 materials

AbstractFor optical temperature sensing materials, the emission and excitation bands are extremely critical to measure the temperature by fluorescence intensity ratio (FIR) technique. Singly Ln‐doped optical temperature sensing materials exhibit very few emission bands, which greatly constraints their practical applications of FIR technique. Here, the fabricated Pr/Er co‐doped (K0.5Na0.5)NbO3 materials exhibited multi‐color (red‐green) and dual‐mode (downshifting/upconversion) luminescence properties. The temperature sensitivity can be effectively tuned by choosing different emission or excitation bands. The optimized optical temperature sensitivity reached up to 0.0094 K−1, much higher than that of most temperature sensing materials. Besides, the samples also showed excellent luminescence modulation properties based on the photochromic reaction. Under sunlight irradiation, the luminescent switching contrast (ΔRt) of the samples reached more than 60%. These results may provide a guiding role in designing and modulating optical temperature sensing properties for multifunctional materials.

Ultrasonic vibration driven piezocatalytic activity of lead-free K0.5Na0.5NbO3 materials

Piezoelectric catalysis is the catalytic action driven by the force-electrical conversion of piezoelectric materials. In this paper, the piezoelectric activity of K0.5Na0.5NbO3 (KNN) was thoroughly investigated by annealing KNN at a series of temperatures and poling KNN under different electric-fields. With the application of an ultrasonification, the degradation activity for the Rhodamine B (RhB) dye molecules of the poled KNN was 253% higher than that of unpoled samples. The piezocatalytic activity of the poled KNN was significantly improved, which stemmed from the orderly ferroelectric domain to effectively reduce the recombination rate of the carriers by the built-in electric field. In addition, the superior piezocatalytic activity was achieved at KNN materials with the average grain size of ~0.29 μm, and after 160 min of mechanical vibration, the degradation rate of RhB (~5 mg/L) was as high as 95.7%. The high mechanical catalytic degradation rate of KNN materials reveals a bright application prospects in vibration catalytic degradation of organic pollutants.

Defect structure, ferroelectricity and piezoelectricity in Fe/Mn/Cu-doped K0.5Na0.5NbO3 lead-free piezoelectric ceramics

For perovskite Pb-based ceramics, outstanding hardening piezoelectric properties can be easily induced by acceptor dopings of Fe, Mn or Cu, but in this work, completely different hardening effects are observed in Fe/Mn/Cu-doped K0.5Na0.5NbO3 ceramics. Pure K0.5Na0.5NbO3 exhibits a well-saturated single P-E loop, giving low Qm of 72. Fe2O3-doped ceramic exhibits the combined effects of dominant donor and slight acceptor, giving a slightly slanted single P-E loop and relatively low Qm of 156. For MnO2-doped ceramic, moderate hardening properties with a slightly pinched P-E loop and relatively high Qm of 370 are exhibited. Unlike Fe2O3 and MnO2-doped ceramics, a double P-E loop and superhigh Qm of 1965 are obtained in CuO-doped ceramic. The defect structure and corresponding microscopic mechanisms in the ceramics have been systematically investigated. Our study shows that defect characteristics should be responsible for distinct hardening properties in Fe, Mn and Cu-doped K0.5Na0.5NbO3 materials.

Hot Pressed K0.5Na0.5NbO3 Material for Piezoelectric Transformer for Energy Harvesting

Hot Pressed K0.5Na0.5NbO3 Material for Piezoelectric Transformer for Energy Harvesting

Dielectric and magnetic properties of three-layers laminated ceramic composite, K0.5Na0.5NbO3/CoFe2O4/K0.5Na0.5NbO3

Three-layers laminated ceramic composite system of K0.5Na0.5NbO3/CoFe2O4/K0.5Na0.5NbO3 (KCK) were prepared by conventional solid state reaction method. SEM analyzes revealed negligible inter-diffusion of chemical elements along the boundary layers in the laminated ceramic composite, KCK. The relative dielectric permittivity of the sandwiched ceramic composite was investigated in a broad frequency range, 101–106 Hz at room temperature. The real part of the relative dielectric permittivity of KCK was strongly frequency dependent; being \(\sim 1250\) and \(\sim 700\) for 100 and 1 KHz, respectively. Also the dielectric study showed a deviation of Cole–Cole relaxation in CoFe2O4 and KNa0.5NbO3 materials to Maxwell–Wagner relaxation in the KCK. It was found that the magnetic properties such as saturation magnetization (\(M_{s}\sim 77\) emu/g), remanent magnetization (\(M_{r}\sim 12\) emu/g) and coercive field (\(H_{c}\sim 320\) Oe ) of KCK were quite the same as ferrimagmetic spinel bulk cobalt ferrite at room temperature.

Comprehensive investigation of Er2O3 doped (Li,K,Na)NbO3 ceramics rendering potential application in novel multifunctional devices

Multifunctional luminescent materials based on rare earth doped ferro-/piezoelectrics have attracted much attention due to their potential applications in novel multifunctional devices. Herein, we choose Li modified (K0.49Na0.51)NbO3 system benefitting from both of the effect of morphotropic phase boundary and polymorphic phase transition as the target materials, and systematically studied the influence of the doping of Er3+ on the phase structure, composition, up-conversion photoluminescence property and so forth. A significantly enhanced ferro-/piezoelectric behavior had been achieved in 0.5% Er2O3 doped (Li,K,Na)NbO3 ceramic. Our results reveal that in addition to the admirable intrinsic piezoelectric properties of (Li,K,Na)NbO3 ceramic, the donor doping behavior of Er3+ could enhance the ferro-/piezoelectric properties and obviously improve the up-conversion photoluminescence property of the matrix materials. These findings show great potential of Er3+ doped (Li,K,Na)NbO3 materials a future application in novel multifunctional devices.

Modified hydrothermal synthesis and structural characterization of monoclinic (KxNa1−x)NbO3 (0.05≤x≤0.15) rods

Monoclinic (KxNa1−x)NbO3 (0.05≤x≤0.15) rods were prepared successfully by the hydrothermal synthesis method combined with dissolution–precipitation and subsequent heat-treatment processes. At first, the primary precipitate of the niobate precursor was obtained using Nb2O5, KOH and NaOH as the initial reactants, and deionized water as the solvent for the hydrothermal synthesis. Interestingly, when the obtained precipitate was dissolved in 90°C of deionized water and then the solution kept standing till ambient temperature, the secondary precipitate of rod-like niobate (KxNa6−x)H2Nb6O19·2H2O was formed. After centrifugation, washing, and the subsequent heat treatment of the secondary precipitate sample, the (KxNa1−x)NbO3 rods of 1–60μm in length and 1–5μm in width were finally prepared. The surface morphology and phase structure of the prouducts were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively, and the chemical composition of the prouducts were identified by means of energy-dispersive X-ray spectroscopy(EDS). Furthermore, fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HRTEM) were employed to investigate the fine structures of the prouducts. This research provides a new approach for the preparation of one-dimensional (KxNa1−x)NbO3 material and template grains for the fabrication of lead-free textured alkali niobate piezoelectric ceramics.

Low-Temperature Synthesis of Perovskite-Type (Na,K)NbO3 through Nb6O198− Clusters by Dissolution–Precipitation Method

Abstract We successfully synthesized perovskite-type (Na1−xKx)NbO3 materials from a Na3NbO4 precursor at low temperature by dissolution–precipitation method. The Nb6O198− cluster was formed as an intermediate by the dissolution of Na3NbO4 into a buffer solution (pH 7). White powders were precipitated by the addition of 1 M NaOH/KOH mixed aqueous solution. We found that the morphology and crystal structure depended on the NaOH/KOH ratio. When the concentration of KOH [CKOH = KOH/(NaOH + KOH)] was low (0 ≤ CKOH ≤ 0.3), rod-like (Na,K,H3O)8Nb6O19·14H2O was precipitated. In the case of high CKOH (0.5 ≤ CKOH ≤ 0.9), (Na0.5K0.5)8Nb6O19·9H2O, whose morphologies changed from hexagonal plate-like to truncated hexagonal bipyramidal structures with the increase in the CKOH, was formed. The (Na,K,H3O)8Nb6O19·14H2O and (Na0.5K0.5)8Nb6O19·9H2O mixture was precipitated using a NaOH/KOH solution with CKOH = 0.4. No precipitation was obtained by the addition of the KOH solution. These precipitations transformed into perovskite-type (Na,K)NbO3 while maintaining their morphology by calcination at 500 °C. The excess Na and/or K were washed out with water. From the lattice constants, the rod-like (Na1−xKx)NbO3 with 0 ≤ x ≤ 0.2 and the hexagonal plate-like or the truncated hexagonal bipyramidal (Na0.5K0.5)NbO3 were synthesized from the rod-like (Na,K,H3O)8Nb6O19·14H2O (0 ≤ CKOH ≤ 0.3) and the hexagonal plate-like or the truncated hexagonal bipyramidal (Na0.5K0.5)8Nb6O19·9H2O (0.5 ≤ CKOH ≤ 0.9), respectively.

SPONTANEOUS POLARIZATION OF SOME (Na,K)NbO3 CERAMICS

Measurements of spontaneous and remanent polarizations of (Na,K)NbO₃ materials near the antiferroelectric boundary are made to provide needed information. Spontaneous polarization of about 30 mu coulombs/cm/sup 2/ is obtained from hysteresis measurements. Values obtained are reasonable considering usual ferroelectric behavior. (D.C.W.)