The domain structure of orthorhombic Li-0.02(K0.45Na0.55)(0.98)NbO3 [LiKNN] ceramics was investigated. Facetted interfaces and abnormal grain growth was observed in the microstructure of these LiKNN ceramics, which consisted of both large and small grains. A rectangular grain surrounded by facetted grain boundaries was observed, and the bright-field image and SAD pattern indicated that these boundaries belong to {100} planes. 90 degrees, 60 degrees, 180 degrees, and S-type domain walls were observed in the grains as well. In fine grains, simple lamellar twinning was predominant; in coarse grains, twinning with a band structure released the elastic stress.

Keywords: KNN; Orthorhombic; Ceramics; Domain; Grain size