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1.
The pure and Mn-doped K0.5Na0.5NbO3 (KNN) films were deposited using solution-gelation method. The crystal structure, ferroelectric properties, spectral response and J-V performance of photovoltaic effect were systematically investigated. Both the ferroelectric and leakage properties are obviously enhanced for Mn-doped KNN films. A fascinating phenomenon is observed that the ferroelectric photovoltaic effect is enhanced in Mn-doped KNN films, which is originated from the improved ferroelectric polarization and narrower band gap. The transition element Nb partially substituted by Mn results in the lattice distortion and further destroys the symmetry space structure, which enhances ferroelectric polarization. And the narrower band gap effectively decreases the internal potential barrier to separate the carriers. This work gives a clear relationship between the lattice distortion, ferroelectric and photovoltaic response. It is certain that lead-free transparent K0.5Na0.5NbO3 films can be potentially applied in viable ferroelectric based solar cells. 相似文献
2.
Er3+ doped K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramics were synthesized by the solid-state reaction method. The upconversion emission properties of Er3+ doped KNN ceramics were investigated as a function of Er3+ concentration and incident pumping power intensity. Bright green (~555 nm) and red (670 nm) upconversion emission bands were obtained under 980 nm excitation at room temperature, which are attributed to (2H11/2, 4S3/2)→4I15/2 and 4F9/2→4I15/2 transitions, respectively. The upconversion emission intensity can be adjusted by changing Er3+ concentration, and the mechanism of upconversion processes involve not only a two-photon absorption but also a three-photon absorption. In addition to the admirable intrinsic piezoelectric properties of KNN, this kind of material may have potential application as a multifunctional device by integrating its upconversion and piezoelectric property. 相似文献
3.
Baoyu Deng Jiahao Jiang Hong Li Chunlin Zhao Cong Lin Xiao Wu Min Gao Tengfei Lin 《Journal of the American Ceramic Society》2022,105(9):5774-5782
Through mixing the KMnO4 solution with K0.5Na0.5NbO3 (KNN) powders, cold sintering process (CSP) was employed to fabricate high-density Mn-doped KNN green pellets and ceramics. The microstructure, doping effect of Mn and electrical properties of these ceramics were studied in detail. Compared with conventional sintering (CS), the CSP supports the homogeneity of dopants and then promotes grain growth and ceramic densification; thus the Mn-doped KNN ceramics prepared by CSP show the obviously higher density and larger grain size. Besides, the less alkalis volatilization and oxygen vacancies result in more Mn3+ but less Mn4+ in CSP ceramics compared to CS ones, which endows the pinning effect and good poling characteristics in CSP ceramics. All the previous results contribute to the high dielectric constant and remnant polarization in CSP ceramics, which support the enhanced piezoelectric coefficient and are much superior than Mn-doped KNN ceramics prepared by CS. This work reveals that CSP can be a new doping strategy to perform chemical modification of electrical properties in KNN ceramics. 相似文献
4.
In this work, Li-modified KNN ceramic compositions ((K0.5Na0.5)1−xLix)NbO3 with x = 0.03, 0.04, 0.05, 0.06, 0.65 and 0.07 were prepared by a conventional solid-state mixed-oxide method. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been found that a morphotropic phase boundary (MPB) between orthorhombic phase and tetragonal phases should exist between compositions with Li contents of 6-6.5%. The Curie temperature (Tc) of the ceramics shifted to higher temperature with increasing Li content. The room temperature dielectric constant was also seen to be higher than the pure KNN ceramics. In addition, the ferroelectric properties were found to enhance at near MPB compositions. This study clearly showed that the addition of Li could improve the dielectric and ferroelectric properties in (K0.5Na0.5)NbO3 ceramics. 相似文献
5.
F. Jean F. Schoenstein M. Zaghrioui M. Bah P. Marchet J. Bustillo F. Giovannelli I. Monot-Laffez 《Ceramics International》2018,44(8):9463-9471
K0.5Na0.5Nb1-xTaxO3 (KNNT) (with x?=?0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830?°C for 5?h. Subsequent sintering of centimeter size pellets, 1–2?mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x?=?0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960?°C, under 50?MPa, for 5–10?min with heating rates of 100?°C/min. High relative permittivity (εr =?1027), piezoelectric charge coefficient (d33 =?160 pC/N) and piezoelectric coupling factor (kp =?46%) are obtained in spark plasma sintered K0.5Na0.5Nb1-xTaxO3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system. 相似文献
6.
Janez Bernard reja Benan Tadej Rojac Janez Holc Barbara Mali Marija Kosec 《Journal of the American Ceramic Society》2008,91(7):2409-2411
The objective of this work was to lower the sintering temperature of K0.5 Na0.5 NbO3 (KNN) without reducing its piezoelectric properties. The KNN was sintered using 0.5, 1, 2, and 4 mass% of (K, Na)-germanate. The influence of the novel sintering aid, based on alkaline germanate with a melting point near 700°C, on the sintering, density, and piezoelectric properties of KNN is presented. The alkaline-germanate-modified KNN ceramics reach up to 96% of theoretical density at sintering temperatures as low as 1000°C, which is approximately 100°C less than the sintering temperature of pure KNN. The relative dielectric permittivity (ɛ/ɛ0 ) and losses (tanδ), measured at 10 kHz, the piezo d 33 coefficient, the electromechanical coupling and mechanical quality factors ( k p , k t , Q m ) of KNN modified with 1 mass% of alkaline germanate are 397, 0.02, 120 pC/N, 0.40, 0.44, and 77, respectively. These values are comparable to the best values obtained for KNN ceramics sintered above 1100°C. 相似文献
7.
《Ceramics International》2022,48(1):22-31
A novel strategy of enhancing the dielectric and energy storage properties of Na0.5Bi0.5TiO3–BaTiO3 (NBT–BT) ceramics by introducing a K0.5Na0.5NbO3 (KNN) ferroelectric phase is proposed herein, and its underlying mechanism is elucidated. The lead-free KNN ceramic decreases the residual polarisation and increases the electric breakdown strength of the NBT–BT matrix through the simultaneous modification of its A-sites and B-sites. The obtained NBT?BT?x?KNN ceramics have a perovskite structure with unifying grains. A bulk 0.9NBT–BT–0.1KNN ceramic sample with a thickness of 0.2 mm possesses a high energy storage density of 2.81 J/cm3 at an applied electric field of 180 kV/cm. Moreover, it exhibits good insulation properties and undergoes rapid charge and discharge processes. Therefore, the obtained 0.9NBT–BT–0.1KNN ceramic can be potentially used in high-power applications because of its high energy density, good insulation properties, and large discharge rate. 相似文献
8.
《Journal of the European Ceramic Society》2020,40(8):2970-2976
(K0.5Na0.5)NbO3 (KNN) + x (= 1, 0.5, 0.05, and 0) wt%Co3O4 single crystals were fabricated by a solid-state crystal growth method with a KTaO3 seed crystal and a KNN atmosphere powder, and the effects of the sintering aid content x and the addition of Co3O4 to the atmosphere powder on the growth of the single crystals were investigated. The formation of pores in the single crystals was suppressed by a decrease of x, which, however, decreased the crystal growth length. On the other hand, dense and large KNN single crystals could be fabricated by sintering with a KNN + 5 wt%Co3O4 atmosphere at x = 0. The dielectric, ferroelectric, and piezoelectric properties of the KNN single crystals were comparable to those of reported (K,Na)NbO3 single crystals. These results would be useful for fabricating dense and large single crystals by the solid-state crystal growth method. 相似文献
9.
《Ceramics International》2021,47(20):28797-28805
K0.5Na0.5NbO3 (KNN) particles were prepared by a solid–state method. X–ray diffraction, scanning electron microscopy, UV–visible spectrophotometry, and electrochemical impedance spectroscopy were used to study the structure, morphology, and properties of the samples. The obtained KNN is a ferroelectric material with orthorhombic perovskite structure at room temperature. The KNN particles can be used as piezo/photo–bicatalysts for degrading organic pollutants by utilizing vibrational and solar energy; the catalytic activity of the particles can be significantly improved owing to their polarization under an applied electric field. Poled KNN particles show a bicatalytic degradation ratio of rhodamine B (RhB) dye reaching 92% after 60 min. The results indicate that the KNN particles can be applied as attractive ferroelectric catalysts for organic pollutant degradation. 相似文献
10.
《Journal of the European Ceramic Society》2020,40(4):1217-1222
Lead-free (K0.5Na0.5)NbO3-based (KNN) piezoceramics featuring a polymorphic phase boundary (PPB) between the orthorhombic and tetragonal phases at room temperature are reported to possess high piezoelectric properties but with inferior cycling stability, while the ceramics with a single tetragonal phase show improved cycling stability but with lower piezoelectric coefficients. In this work, electric biasing in-situ transmission electron microscopy (TEM) study is conducted on two KNN-based compositions, which are respectively at and off PPB. Our observations reveal the distinctive domain responses in these two ceramics under cyclic fields. The higher domain wall density in the poled KNN at PPB contributes to the high piezoelectric properties. Upon cycling, however, a new microstructure feature, “domain intersection”, is directly observed in this PPB composition. In comparison, the off-PPB KNN ceramic develops large domains during poling, which experience much less extent of disruption during cycling. Our comparative study provides the basis for understanding the relation between phase composition and piezoelectric performance. 相似文献
11.
Novel high temperature ceramic capacitors (1??x)(Na0.5Bi0.5TiO3 ??0.15Ba0.8Ca0.2Ti0.8Zr0.2O3)??xK0.5Na0.5NbO3 were synthesized in the solid-state reaction route. The influence of K0.5Na0.5NbO3 modification on dielectric behavior, energy-storage properties, ac impedance and temperature stable dielectric performance were systematically investigated. The reduced grain size and enhanced relaxor properties are obtained with the addition of KNN. The content of x?=?0.1 exhibits a stable permittivity (~ 1630) and dielectric loss (<?0.05) over a relatively broad temperature range (66–230?°C). A variation in permittivity within ±?15% can be observed over a pretty wide temperature range of 66–450?°C. Beyond that, this ceramic shows enhanced energy-storage properties with the density (Wrec) of 0.52?J/cm3 and efficiency (η) of 80.3% at 110?kV/cm. The possible contributions of the grain and the grain boundary to the ceramic capacitance are discussed by the ac impedance spectroscopy. 相似文献
12.
《Ceramics International》2020,46(8):11617-11621
Lead-free Na0.5K0.5NbO3 (KNN) piezoelectric ceramics is regarded as a potential candidate for PZT material, while high performance is difficult to be obtained due to its poor sinterability and non-stoichiometric component. In this work, oscillatory pressure-assisted hot pressing (OPAHP) is utilized to fabricate KNN ceramics with high density. The KNN ceramics sintered at 860 °C exhibits superior performance with piezoelectric parameter (d33) of 142 pC/N, electromechanical coupling factors (kp) of 0.41, and relative permittivity (εT33/ε0) of 472–620. Additionally, hardness and flexural strength are measured as 3.55 GPa and 99.13 MPa, respectively. This work indicates that OPAHP technique is effective for fabricating KNN piezoelectric ceramics with high performance. 相似文献
13.
Tao Wang You Liao Dongmei Wang Qiaoji Zheng Jie Liao Fengyu Xie Wenjing Jie Dunmin Lin 《Journal of the American Ceramic Society》2019,102(1):351-361
For accepter-doped perovskite piezoelectric ceramics, macroscopic properties of the materials (eg, hardening, fatigue, and aging) are closely related to microscopic characteristics (eg, oxygen vacancies and defect dipoles). In this work, the relationship of macroscopic and microscopic characteristics in CuO-doped K0.5Na0.5NbO3 (KNN) ceramic has been studied by subjecting the material to electric field cycling, quenching, heating, and consequently aging. The introduction of CuO in KNN generates and . The defect dipoles exhibit obviously the pinning effect on ferroelectric domains and thus induce a completely pinched/double P-E loop and excellent hardening piezoelectricity of high Qm of 2235. With the destruction of short-range symmetry uniformity between defect dipoles and ferroelectric dipoles induced by electric field cycling, quenching and heating, the ceramic can be depinned and softened. As a result, the depinned ceramic possesses an opened single ferroelectric hysteresis loop and the significantly decreasing Qm. A distinctive aging is observed in the depinned ceramic. This study provides deep insights into the evolution of electrical properties of accepter-modified alkali niobate perovskite ceramics under electric field cycling, quenching, and heating. 相似文献
14.
Jianzhang Ma Hanying Li Huajing Wang Cong Lin Xiao Wu Tengfei Lin Xinghua Zheng Xing Yu 《Journal of the European Ceramic Society》2019,39(4):986-993
In this paper, cold sintering was served as a forming method to assist the conventional sintering, which is so-called cold sintering assisted sintering (CSAS) method. Lead-free K0.5Na0.5NbO3 piezoelectric ceramics were prepared by the CSAS method, and the effects of the different procedures on the sintering behaviors and electrical properties of KNN ceramics were studied. Compared with conventional sintering (CS), cold sintering process can induce potassium-rich phase on the KNN particle surface, and remarkably increase both the green and sintering density of KNN ceramics. Meanwhile, the potassium-rich phase would transform to K4Nb6O17 second phase on the grain surface, and subsequently suppress the volatilization of potassium element. The sinterability and electrical properties were greatly improved, and KNN piezoelectric ceramics with high performance can be manufactured in a wide sintering temperature range (1055 °C–1145 °C), which proves that CSAS has the potential to be an excellent sintering technique for producing KNN based ceramics. 相似文献
15.
A solid state metathesis approach has been applied to synthesize perovskite oxides such as BaTiO3, PbTiO3, K0.5Bi0.5TiO3 and Na0.5Bi0.5TiO3, these were characterized by powder XRD, IR and energy dispersive spectra (EDS). Potassium titanium oxalate and metal chlorides are used as the starting materials. X-ray analysis shows the formation of a single phase with tetragonal structure for BaTiO3, PbTiO3, K0.5Bi0.5TiO3 and a monoclinic structure for Na0.5Bi0.5TiO3. The Infrared spectra of these compounds show the characteristic band due to Ti–O octahedron for all the compounds. The EDS spectra show the relative ratio of the metal ions. The morphology of synthesized compounds was obtained from SEM measurements. 相似文献
16.
Pengfei Yin Yu Deng Limin Zhang Wenjuan Wu Jian Wang Xing Feng Xiyuan Sun Huayao Li Yu Tao 《Ceramics International》2018,44(17):20896-20905
Ni0.5Co0.5Fe2O4/graphene composites were synthesized successfully via one-step hydrothermal method. The crystal structure, morphology and corresponding elemental distribution, electromagnetic parameters and microwave absorption performances of the as-prepared composites were measured by XRD, SEM, TEM and VNA, respectively. The results indicated that the microwave absorbing performance can be obviously enhanced through the addition of graphene in a suitable range, the magnetic loss plays a dominant contribution for the microwave absorption of composites. The maximum reflection loss of ?30.92?dB at 0.84?GHz with a ?10?dB bandwidth over the frequency range of 0.58–1.19?GHz is obtained when the composite contains 12?wt% graphene and the thickness of sample is 4?mm. This investigation presents a simple method to prepare Ni0.5Co0.5Fe2O4/graphene composites with excellent microwave absorption performance in the low frequency band of 0.1–3?GHz. 相似文献
17.
《Ceramics International》2021,47(22):31811-31816
We fabricated a ZrO2/Al2O3 ceramic using the 3D plasma spraying technology, and the surface morphology and electrical properties of the prepared ceramic were investigated. The microwave-absorbing performance of the ceramic was studied based on the measured electrical properties. Furthermore, a radar-absorbing structure (RAS) was designed based on the fabricated ZrO2/Al2O3 ceramic with a K0.5Na0.5NbO3 (KNN) film heterojunction. The relationship between the structural parameters of the RAS and the microwave performance was explored. The changes in the absorption performance and band structure of the RAS with the resistance of the KNN film were investigated. The analytical results showed that the structural parameters of the KNN film can facilitate the absorption intensity as well as the bandwidth of the RAS while inducing electromagnetic coupling in the RAS system. The improvement in the absorption performance could be attributed to the resonance coupling between the ZrO2/Al2O3 ceramic and the KNN film. 相似文献
18.
Ta-doping K0.5Na0.5Nb1−xTaxO3 (x = 0.1, 0.2, 0.3, 0.4) powder was synthesized by hydrothermal approach and its ceramics were prepared after sintering and polarizing treatment in this work. The K0.5Na0.5Nb0.7Ta0.3O3 ceramics near morphotropic phase boundary (MPB), which exhibited optimum piezoelectric properties of d33 = 210 pC/N and good electromechanical coupling factors of Kp = 0.3. The domain structure has been observed from TEM images which indicates that the K0.5Na0.5Nb0.7Ta0.3O3 ceramics have good piezoelectric and ferroelectric properties for it is near the MPB. 相似文献
19.
《Ceramics International》2023,49(3):4074-4081
Photochromic (PC) materials have potential applications in the fields of memory, anti-counterfeiting due to their reversible writable/erasable properties. The common organic PC films are restricted during applications owing to the strict requirements of thermal stability and waterproof of devices. Additionally, most of the PC materials strongly rely on external conditions (irradiation/heat) to realize reversible PC regulations, which may cause irreversible damage to devices (reduce the performance and service life). Hence, it is imperative to develop new inorganic membrane materials with PC self-recovery behavior. Here, a novel strategy to achieve completely reversible PC regulation based on the K0.5Na0.5NbO3 (KNN) based thick films is reported. It is worth noting that the PC self-recovery behavior can be optimized via forming the inter-electronic-levels in the band gap via Tm/Yb co-doping in KNN, alleviating the barrier of carrier transition from valence band to conduction band and heightening the recombination efficiency of carriers. And the obtained thick films manifest a reversible PC self-recovery reaction within 6 min. This work is expected to provide the effective guidance for facilitating the further utilization of PC materials. 相似文献
20.
Y.J. Han Y.Z. Wang C.H. Yang Q. Yao J. Chen S.F. Huang 《Ceramics International》2018,44(13):15153-15159
This work reports the characteristics of nonstoichiometric Na0.5+xBi0.5+yTi0.96W0.01Ni0.03O3 (x?=?0.0%, y?=?1.0%; x?=?0.5%, y?=?2.0%; x?=?1.0%, y?=?4.0%) ceramic films derived from chemical solution deposition and the role played by excess Na/Bi in modifying microstructure and electrical properties. Single perovskite phase structure can be maintained in all compositions. Decreased grain size can be obtained with the increasing compensation for volatile Na/Bi elements. Particularly, extra amounts of 0.5?mol% Na and 2.0?mol% Bi leads to reduced leakage and enhanced ferroelectric polarization. Meanwhile, due to the high breakdown electrical field strength and large difference between maximum and remanent polarization, an excellent energy storage performance can be achieved in Na0.505Bi0.52Ti0.96W0.01Ni0.03O3 sample, which is distinguished by a recoverable energy storage density of 40.5?J/cm3 and an energy storage efficiency of 43.6% at 2515?kV/cm as well as a good frequency stability. Hence, the regulation for the content of volatile elements is effective to modify the electrical response of Na0.5Bi0.5TiO3-based materials. 相似文献