Influence of sintering conditions on piezoelectric properties of KNbO3 ceramics

High Resolution Transmission Electron Microscopy Observations on Sintering Processes in KNbO3 Ceramics

“…However, the sintering temperature used in this method was 1,050 o C, which is very close to the melting temperature of KN ceramics (1,058 o C) (Irle et al, 1991). Recently it was reported that the homogeneous KN phase was developed in the specimens sintered at 1,020 o C and 1,040 o C without the formation of the K 2 O-deficient secondary phase and a small amount of the KN phase melted during sintering and assisted the densification and the abnormal grain growth (Kim et al, 2014). In present investigations, the detailed observations on the sintering mechanism of KN ceramics were carried out using high resolution transmission electron microscopy (HRTEM).…”

“…When the liquid phase fails to recrystallize, it remains as the solid amorphous phase. Kim et al (2014) ions existing in the liquid phase was 1.0:1.3. A similar result was also observed in the matrix phase.…”

“…The thickness and diameter of each specimen were 1.0 and 14.0 mm, respectively. The detailed sample preparations and their electrical properties are described elsewhere (Kim et al, 2014). The transmission electron microscopy (TEM) specimens were obtained by ultrasonic cutting into 3 mm diameter disks and then mechanically polishing to a thickness of 100 μm.…”

Band gap evolution and a piezoelectric-to-electrostrictive crossover in (1 − x)KNbO3–x(Ba0.5Bi0.5)(Nb0.5Zn0.5)O3 ceramics

“…In ceramics, the roomtemperature ε r was been report to vary between ~300 and 800. [12][13][14][15] This wide range on ε r values is linked to several aspects of the final microstructures, such as variations on density, texture and grain sizes. Fabrication of KN ceramics is difficult with problems mainly associated with unsuccessful densification, due to its low melting temperature (< 1100°C).…”

“…In addition, the structural stability of KN ceramics encompassing residual K 4 Nb 6 O 17 is dramatically affected by moisture. To minimise the detrimental effects of moisture, several authors studied the impact of processing conditions 13,16,17 on KN and prescribed remedial procedures 14,15 . In addition, the conduction band minimum (CBM) which consists mainly of the Nb 4d states is essentially preserved from the parent KNbO 3 .…”