Synthesis of potassium–sodium niobate (KNN) from NbO2

Piskin, Cerem; Karacasulu, Levent; Bortolotti, Mauro; Vakifahmetoğlu, Çekdar

doi:10.1016/j.oceram.2021.100159

Cited by 8 publications

(5 citation statements)

References 40 publications

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“…Together with the depletion of the secondary NaNbO 3 phase, such a shift implies that sodium occupancy was increased, resulting in the formation of K 0.58 Na 0.42 NbO 3 . In other words, proximity to the stoichiometry corresponding to the MPB, that is,

x\, \cong 0.5

(K 0.5 Na 0.5 NbO 3 ), where the piezoelectrical properties maximize, was obtained, akin to previous works 42,59,77 …”

Section: Resultsmentioning

confidence: 57%

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Hydrothermal synthesis of potassium–sodium niobate powders

et al. 2022

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Potassium–sodium niobates (KxNa1−xNbO3, 0 < x < 1, KNN) were hydrothermally synthesized under varying alkaline ratios (K+/Na+), total hydroxide concentration, reaction temperature, and time. Compositional surveys were developed by using Rietveld analyses derived quantitative volume fractions. The data demonstrated that phase pure KNN synthesis can be achieved by reacting the niobium source with the hydroxide solution having 6 M total hydroxide concentration, cation ratio (K+/Na+) of above 6 at temperatures ≥200°C for 24 h. Dissolution–precipitation events through intermediate products including hexaniobates were postulated as a plausible formation mechanism. It was shown also that the single‐phase KNN approaching the morphotropic phase boundary (MPB) could be obtained by further incorporation of sodium ions into the crystal via post‐annealing at 800°C/2 h, following the hydrothermal synthesis.

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x\, \cong 0.5

(K 0.5 Na 0.5 NbO 3 ), where the piezoelectrical properties maximize, was obtained, akin to previous works 42,59,77 …”

Section: Resultsmentioning

confidence: 57%

“…In other words, proximity to the stoichiometry corresponding to the MPB, that is, 𝑥 ≅ 0.5 (K 0.5 Na 0.5 NbO 3 ), where the piezoelectrical properties maximize, was obtained, akin to previous works. 42,59,77…”

Section: Plausible Formation Mechanismmentioning

confidence: 99%

Hydrothermal synthesis of potassium–sodium niobate powders

et al. 2022

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“…The existence of the secondary phases is somewhat expected in double calcination and sintering process since the raw materials for the solid-state synthesis which are generally alkali carbonates have hygroscopic nature, thus resulting in poor purity. Therefore, when the sample was subjected to double calcination and sintering, the deviations in KNN stoichiometry might occur due to uneven volatilization of the alkali oxides (Na2O and K2O) takes place as a result of their relatively high volatility [6] due to twice calcination and milling. It is suggested that to achieved a pure orthorhombic phase of KNN with higher densification, the sintering atmosphere should be controlled as this sintering atmosphere could affect the existence of oxygen vacancies in KNN based ceramics [14,15].…”

Section: (B) Sinteringmentioning

confidence: 99%

“…KNN may be synthesised using several different techniques, including hydrothermal, microwave, hot press, sol-gel, and many others [5,6,7]. The majority of these methods have been enhanced to produce structures with exceptional piezoelectric characteristics.…”

Section: Introductionmentioning

confidence: 99%

Influence of Double Calcination-Milling Route on the Structural and Microstructural Properties of Lead-Free K0.5NA0.5NBO3 (Knn) Ceramics

et al. 2023

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Potassium sodium niobate (KNN) has always been one of the most potential candidates to replace lead-based piezoelectric ceramics due to its strong piezoelectric properties and environmentally friendly composition. A strong piezoelectric property is constantly influenced by the sample's densification as well as its microstructural characteristics. One of the current main issues with this KNN lead-free piezoelectric material is the difficulty in creating high-density samples by conventional preparation and sintering. Thus, KNN lead-free ceramics were synthesised using an improved solid-state method by introducing the double calcination-milling route to this process. The outcome demonstrates that, despite the presence of additional KNN secondary phases, the double calcination-milling approach contributed to the early creation of the KNN phase. When sintered pellets are subjected to a double calcination milling process, the XRD pattern revealed that the main peaks of the sample are indexed to orthorhombic K0.5Na0.5NbO3. The double calcination KNN pellet have a relative density of 90% densification which is slightly higher than that of single calcination KNN pellet which shows 88% densification.

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“…Recently, various approaches to the synthesis of KNN piezoelectric materials have been attempted, including solid-state reaction [9,13,22,23], spark plasma sintering [24], microwave heating method [25], molten-salt process [20], the Pechini method [21], the sol-gel method [26][27][28], and the hydrothermal method [10,17,[29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Facile Glycothermal Synthesis of KxNa(1−x)NbO3 Particles

2022

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KxNa(1−x)NbO3 particles (KNN, 0 < × < 1) were successfully synthesized through a facile glycothermal method by using KOH, NaOH and Nb2O5 as precursors and 1,4-butanediol as solvent at 200 °C for 12 h. The effects of varying the 1,4-butanediol/deionized water (B/W) volume ratio as solvent on the growth behavior, the morphological evolution, and the particle size of the synthesized KNN particles were investigated. In order to obtain K0.5Na0.5NbO3 with the morphotropic phase boundary (MPB) at the potassium content of x ≈ 0.5, the effect of varying K+/Na+ molar ratio on the composition of the obtained KNN particles was investigated. The crystal phase structure, morphology, particle size, chemical composition, and thermal behavior of the obtained particle samples were characterized using XRD, FE-SEM, EDS, TG, FT-IR, PSA, and TEM. The pure orthorhombic KNN particle close to NaNbO3 phase was obtained at the same concentration K+/Na+ of 1.0/1.0 and [K++Na+]/Nb molar ratio of 2.0/0.1. The synthesized K0.01Na0.99NbO3 particle exhibited a hexahedron shape with an average crystallite size of approximately 400 nm by glycothermal treated at 200 °C for 12 h. It is also demonstrated that the size of Na-rich KNN particles was decreased from 15 µm to 400 nm with increasing 1,4-butanediol content at various reaction conditions such as the volume ratio of B/W and can be controlled by 1,4-butanediol with an additive of water. Until the molar ratio of K+/Na+ reaches 1.6/0.4, the obtained particles have produced a Na-rich KNN phase, whereas when the molar ratio of K+/Na+ is 1.8/0.2, the particles could obtain a K-rich KNN phase. The results revealed that single-phase K0.5Na0.5NbO3 particles could be obtained at a relatively narrow molar ratio of K+/Na+ to 1.7/0.3. The particles with weakened agglomerate could obtain the average particle size of approximately 400 nm and a hexahedron shape. In comparison with the traditional hydrothermal method, the glycothermal method has been confirmed to be a more efficient method in controlling the particle size of KNN particles from micro- to sub-micron.

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Synthesis of potassium–sodium niobate (KNN) from NbO2

Cited by 8 publications

References 40 publications

Hydrothermal synthesis of potassium–sodium niobate powders

Hydrothermal synthesis of potassium–sodium niobate powders

Influence of Double Calcination-Milling Route on the Structural and Microstructural Properties of Lead-Free K0.5NA0.5NBO3 (Knn) Ceramics

Facile Glycothermal Synthesis of KxNa(1−x)NbO3 Particles

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