A Novel Low Temperature Synthesis of KNN Nanoparticles by Facile Wet Chemical Method

Abstract

Sodium potassium niobate (KNN) (K 0.5 Na 0.5 NbO 3 ) nanopowder with a mean particle size of about 20 -30 nm was synthesized by wet chemical route using Nb 2 O 5 as Nb source. A solution of K, Na and Nb cations was prepared, which resulted in a clear gel after the thermal treatment. Phase analysis, microstructure and morphology of the powder were determined by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The obtained gel was first analyzed by Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC), and then calcined at different temperatures of 400˚C, 500˚C, 600˚C and 700˚C. The X-Ray Diffraction (XRD) patterns of the synthesized samples confirmed the formation of the orthorhombic crystal phase of K 0.5 Na 0.5 NbO 3 at 500˚C, a temperature significantly lower than that typically used in the conventional mixed oxide route. The process developed in this work is convenient to realize the mass production of KNN nanopowders at low cost and suitable for various industrial applications.

Local Piezoelectric Behavior of Potassium Sodium Niobate Prepared by a Facile Synthesis via Water Soluble Precursors

“…A similar result, in terms of low calcination temperature, was obtained by Stavber and co‐authors, which produced pure KNN (K:Na = 1) starting from ammonium niobium oxo‐tris(oxalate) monohydrate and potassium and sodium nitrate . Recently, also Rani et al synthesized K 0.5 Na 0.5 NbO 3 powders by sol‐method but, at the same temperature of calcination of 500 °C, the final product showed a lower crystallinity (average size domain extension ≈ 240 Å) accompanied by the presence of an undesired secondary phase (K 3 Nb 6 O 17 ) …”

“…In the left side micrograph (Figure A), the surface of the post‐heated gel shows the clear presence of pores ascribable to the release of CO 2 gas during the annealing process. The CO 2 evolution is a consequence of the thermal decomposition of the complex oxalates formed through the gelation, as it was already observed by Yao et al and further confirmed by Rani and coauthors . Upon compaction and subsequent annealing at 500 °C, the surface morphology of the final pellet changes with respect to the un‐treated powders.…”

“…However, the high cost and easiness to hydrolysis of niobium alkoxides are limiting factors of these processes for scaling up applications . Niobium (V) oxide is considered a good alternative as Nb precursor for its low cost and for the possibility to obtain metal complexes with chelating species in water The principle of this method is that hydroxycarboxylic acids, amino acids, or some other natural organic compounds are used to protect and stabilize high valence metal ions, activating them to enhance solubility and reactivity in water. On the other hand, the many steps involved in the preparation process with niobium oxide reagent, are time consuming and imply drawbacks for the use of hydrofluoric acid (HF) in order to prepare niobic acid or at high temperature .…”

<i>Stachytarpheta cayennensis</i> Aqueous Extract, a New Bioreactor towards Silver Nanoparticles for Biomedical Applications

“…The Williamson-Hall analysis relies on the principle that the approximate formula for the size broadening and the strain broadening vary quite differently with respect to the Bragg angle [19]. The crystallite size and strain can be obtained from the intercept at y-axis and the slope of line, respectively.…”

“…The negative slope 4ε ofFigure 4indicates that micro-strains cannot be a dominant source of broadening or proves that the strain is compressive while positive value indicates an expansion of the strain[29]. The low values indicate the occurrence of lattice relaxation within nanocrystallites[19]. The nonlinearity between βcosθ and sinθ can be due to low crystallized powder samples[29].Microscopy investigation shows large sized spherical grains that may have grown from the coalescences of small particles.…”