Electron Microscopy Studies of Potassium Sodium Niobate Ceramics

Abstract

Using electron microscopy, K0.5Na0.5NbO3 (KNN) ceramics sintered at 1030 degrees C for 8 h and 1100 degrees C for 2 and 24 h was studied. The scanning electron microscopy and X-ray spectrometry revealed that the materials consisted of a matrix phase in which the (Na+K)/Nb ratio corresponded closely to the nominal composition and a small amount of Nb-rich secondary phase. A bimodal microstructure of cube-shaped grains was revealed in the fracture and thermally-etched surfaces of the KNN. In the ceramics sintered at 1100 degrees C, the larger grains (up to 30 mum across), contained angular trapped pores. The transmission electron microscopy analysis revealed that the crystal planes of the grains bordering the intragranular pore faces were of the {100} family with respect to the simple perovskite cell. Ferroelectric domains were observed in the grains of this material.

Influence of sintering temperature on electrical properties of (K0.4425Na0.52Li0.0375)(Nb0.8825Sb0.07Ta0.0475)O3 ceramics without phase transition induced by sintering temperature

“…With the increase in temperature, the (002) and (200) peaks shift toward lower angles, which is attributed to the easy volatilization of sodium and potassium during high-temperature sintering. Sodium volatilizes faster than potassium, resulting in the presence of a niobium-rich phase [24]. The lattice parameters increase (Fig.…”

Lead-Free Ferroelectric Ceramics with Perovskite Structure

“…5a the bright field and 5b the high resolution images of KNN powders are shown. The typical cubic shape of KNN is clearly seen (Jenko et al, 2005). The KNLNT crystalline powders are shown in Figs.…”

“…The higher density was that of the sample sintered at 1080°C, 4.33 g/cm 3 (96% of theoretical value, 4.51g/cm 3 being the reference value). The low density of the samples sintered at 1100 and 1120°C are due to the formation of liquid phase and the considerable volatilization of alkaline elements (Jenko et al, 2005;López et al, 2011a;. …”

Development of KNN-Based Piezoelectric Materials

“…The melting points of these precursors are 851, 891 and 1,520 C respectively. Since the normal calcination temperature of KNN is close to the melting point of two alkali precursors, they always have the problem of volatilization during calcination and hence deficiency of A site ions [30,34,35]. Effect of calcination temperature, dwell time and excess of alkali carbonates on phase formation and microstructure of KNN is studied extensively [30,36,37].…”