Using electron microscopy,
K0.5Na0.5NbO3 (KNN) ceramics sintered at
1030°C for 8 h and 1100°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°C, the larger grains (up to 30 μm 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.