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High-efficiency synthesis of high-performance K0.5Na0.5NbO3 ceramics
摘要： Pure (K0.5Na0.5)NbO3 (KNN) ceramics with high density, fine and uniform-size grains were prepared by mechanochemical activation-assisted process. The time of synthesis is only 100 min, which is 72% - 93% shorter than the 6-24h of the conventional solid-state method. Compared to samples prepared by conventional solid-state method, both the microstructure evolvement and electric properties were explored in detail. Results show the electric properties was significantly improved. Moreover, the dielectric and ferroelectric properties of obtained KNN ceramics exhibit strong dependence on the crystal size of the initial powders. The optimized ceramics HKNN100 showed a quite high energy storage performance, i.e., large electric energy storage density (Wtol=1.612 J/cm3) and recoverable energy storage density (Wrec=0.431 J/cm3), which can be mainly ascribed to the large dielectric breakdown strength (DBS=110 kV/cm). Our works demonstrated that mechanochemical activation-assisted method possesses advantages for high-efficiency preparation of KNN or KNN-based ceramics.
关键词： Dielectric properties,Ferroelectricity,(K0.5Na0.5)NbO3 Ceramics,Mechanochemical activation,Microstructure
更新于2025-11-14 17:04:02
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[IEEE 2018 IEEE ISAF-FMA-AMF-AMEC-PFM Joint Conference (IFAAP) - Hiroshima (2018.5.27-2018.6.1)] 2018 IEEE ISAF-FMA-AMF-AMEC-PFM Joint Conference (IFAAP) - Domain Switching by Applied Electric Field in (001) and (111)-epitaxial (K<inf>0.5</inf>Na<inf>0.5</inf>)NbO<inf>3</inf>Films
摘要： (K1-xNax)NbO3 (KNN) is especially paid attention to as a lead-free piezoelectric material. It is known that KNN has a morphotropic phase boundary (MPB) at x ~ 0.5, which shows a high piezoelectric property. However, it has not been fully clarified how the domain structure of KNN changes by applied electric field. In this study, we observed electric field-induced strain and domain fraction change of KNN films by synchrotron X-ray diffraction.
关键词： Na)NbO3,domain switching,films,(K
更新于2025-09-23 15:23:52
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Deposition of orientation-controlled thick (K,Na)NbO<sub>3</sub> films on metal substrates by repeated hydrothermal deposition technique
摘要： (K,Na)NbO3 thick films were grown at 240°C on Ni-based metal substrates by repeated hydrothermal method. The metal substrates were covered with two types of buffer layers; SrRuO3/LaNiO3 and SrRuO3. Film thickness monotonically increased with increasing number of deposition cycles. The 27 μm-thick film was obtained on the metal substrate with SrRuO3/LaNiO3 by four cycles. The obtained films tended to show {100}c orientation and their degree of orientation increased with increasing number of deposition cycles. Films deposited on SrRuO3/LaNiO3-covered metal substrates showed more highly {100}c orientation compared with those on SrRuO3-covered metal substrates. Remnant polarization and coercive field measured at 5 kHz were 12 μC/cm2 and 70 kV/cm, while their effective values of piezoelectric coefficient (d33) was 35–40 pm/V for both films. These properties remained unchanged irrespective of a number of deposition cycles despite the orientation change of films. These results show that repeated hydrothermal deposition technique is one of the effective ways to prepare thick (K,Na)NbO3 films on metal substrates.
关键词： Metal substrate,Lead-free (K,Na)NbO3 film,Orientation control,Ferroelectric and piezoelectric properties,Hydrothermal,synthesize
更新于2025-09-12 10:27:22
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Temperature-stable dielectric properties from 100 to 375?°C in system (K0.495Na0.495La0.01)(Nb0.997Cu0.0075)O3–Bi(Mg0.5Zr0.5)O3
摘要： (1-x)(K0.495Na0.495La0.01)(Nb0.997Cu0.0075)O3-xBi(Mg0.5Zr0.5)O3 (abbreviated as KNLNC-xBMZ) ceramics were designed and prepared. The phase transition, microstructure and electrical properties of the ceramics were investigated. The phase structures of the ceramics transform from orthorhombic to pseudocubic phases and the grain sizes decrease gradually with BMZ content (x) increasing. Additionally, BMZ additions can significantly enhance the dielectric temperature stability and decrease the dielectric loss of ceramics over a relatively broad temperature range. KNLNC-0.02BMZ ceramics exhibit high dielectric permittivity (er = 1542) and small variation (Der/er150 (cid:2)C B ± 15%) in dielectric permittivity from 100 to 375 (cid:2)C, and low dielectric loss (tand B 2%) in the temperature range of 100–350 (cid:2)C, which suggests that this ceramic is a candidate for high-temperature capacitor application.
关键词： (K0.5Na0.5)NbO3,Lead-free,Dielectric properties,Elevated temperature stability,Microstructure
更新于2025-09-10 09:29:36
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Piezoelectric Materials || Piezoelectric Properties and Microstructure of (K,Na)NbO3– KTiNbO5 Composite Lead-Free Piezoelectric Ceramic
摘要： We developed a (K,Na)NbO3-based lead-free piezoelectric ceramic with a KTiNbO5 system, (K1?xNax)0.86Ca0.04Li0.02Nb0.85O3?δ–KTiNbO5–BaZrO3–Co3O4–Fe2O3–ZnO (KNN–NTK composite). This KNN–NTK composite exhibits a very dense microstructure, ε33T/ε0 = 1600, and d33 = 252 pC/N. We found that a portion of the KTiNbO5 converted into K2(Ti,Nb,Co,Zn)6O13 and/or CoZnTiO4. We were able to reproducibly prepare granulated powder of KNN–NTK in batches of 100 kg using a spray-dryer. In addition, we performed a detailed investigation of the microstructure of KNN–NTK composite. The results show that a tetragonal and an orthorhombic phase coexist in a main KNN phase over a wide range of 0.56 ≤ x ≤ 0.75. The granular nanodomains of the orthorhombic phase dispersed within the tetragonal matrix in the KNN phase. A maximum value of kp = 0.56 occurred for x = 0.56. The Na fraction x corresponding to maximum kp was also the minimum x required to generate the orthorhombic phase. We conclude that the KNN–NTK composite exhibits excellent piezoelectric properties because of the two-phase coexisting state. This gentle phase transition of KNN–NTK composite seems to be a relaxor, but the diffuseness degree γ = 1.07 suggests otherwise.
关键词： coupling coefficient,(K,Na)NbO3,microstructure,two-phase coexisting,lead-free
更新于2025-09-09 09:28:46