Sintering of sub-micron K 0.5 Na 0.5 NbO 3 powders fabricated by spray pyrolysis

Haugen, Astri Bjørnetun; Madaro, Francesco; Bjørkeng, Lars Petter; Grande, Tor; Einarsrud, Mari‐Ann

doi:10.1016/j.jeurceramsoc.2014.11.011

Cited by 41 publications

(43 citation statements)

References 54 publications

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“…Alkali excess in the amount of a few mole % resulted in KNN particles with larger sizes than the stoichiometric or alkali-deficient KNN synthesized under the same processing conditions, cf. ref [33,84,85]. Recently, Haugen et al ., hypothesized that alkali-containing oxides, such as KNN, will react with humidity and carbon dioxide to form surface carbonates and hydroxides that will create a liquid phase upon heating and promote the coarsening of particles.…”

Section: Sodium Potassium Niobate Systemmentioning

confidence: 99%

“…Recently, Haugen et al ., hypothesized that alkali-containing oxides, such as KNN, will react with humidity and carbon dioxide to form surface carbonates and hydroxides that will create a liquid phase upon heating and promote the coarsening of particles. Such an effect would be even more pronounced in the case of fine particles with a high surface area [85]. …”

Section: Sodium Potassium Niobate Systemmentioning

confidence: 99%

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Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

et al. 2015

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The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT).

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Section: Sodium Potassium Niobate Systemmentioning

confidence: 99%

Section: Sodium Potassium Niobate Systemmentioning

confidence: 99%

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

et al. 2015

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“…Although their grain size distribution is totally different, the density of all samples is around 4.5 g/cm 3 . Based on literatures, the grain size distribution can be affected by both liquid phase and vacancies . For ceramics with excess niobium content, liquid phase and decreased vacancies can promote the grain growth.…”

Section: Resultsmentioning

confidence: 99%

Defect engineering electrical properties of lead‐free potassium sodium niobate‐based ceramics

Sun

Zheng

et al. 2019

J Am Ceram Soc

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Defect engineering plays an important role in property modification for piezoelectric materials. In this work, we pay much attention to the effect of Nb nonstoichiometry on structure and properties of typical 0.95(K0.45Na0.55)Nb1+xO3–0.05Bi0.5Na0.5HfO3 ceramics. Large piezoelectric constant (d33 ~ 425 pC/N and d33∗ ~482 pm/V) together with high Curie temperature (TC ~ 315°C) have been achieved in the ceramics with excess Nb content (x = 0.01). However, the ceramics with deficient Nb element have seriously suppressed cryogenic εr‐T curves and deteriorated electrical properties. Multi‐scale characterizations including phase structure, microstructure, defect structure and domain structure have been adopted to explain the corresponding phenomenon. Defect complex VNb″″′-VnormalO·· caused by deficient Nb induces clamped domain wall motion, leading to blocked polarization vector and poor electrical properties. On the contrary, the enhanced properties for the ceramics with excess Nb are attributed to easier domain switching due to the suppressed vacancies. We believe that defect engineering, for example nonstoichiometry, cannot only modulate electrical properties but also help us to understand some fundamental and critical problems about KNN‐based ceramics.

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“…Furthermore, studies of multilayer KNN-based lead-free piezoelectric ceramics with silver-palladium electrodes have been reported [74,75]. Moreover, many studies on the application of KNN-based ceramics and improving the piezoelectric properties of KNN-based ceramics have been reported [76,77,78,79,80,81,82,83,84,85,86,87,88,89]. These activities indicate that a KNN-based multilayer ceramic structure is widely considered to be a good candidate for lead-free piezoelectric devices.…”

Section: Discussionmentioning

confidence: 99%

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

et al. 2015

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Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (Smax/Emax) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where Smax denotes the maximum strain and Emax denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed.

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Sintering of sub-micron K 0.5 Na 0.5 NbO 3 powders fabricated by spray pyrolysis

Cited by 41 publications

References 54 publications

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

Defect engineering electrical properties of lead‐free potassium sodium niobate‐based ceramics

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

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