Domain Structure of Poled (K 0.50 Na 0.50 ) 1− x Li x NbO 3 Ceramics with Different Stabilities

Domain structure of several poled (K 0.50 Na 0.50 ) 1− x Li x NbO 3 ceramics (with chemical compositions of x = 0.03, 0.065, and 0.08, respectively) was investigated by means of observing the domain patterns with an acid‐etching technique. Among the three ceramics, the one with x = 0.03 is of orthorhombic phase and the other two are of tetragonal phase at room temperature. It was found that these ceramics possess distinctly different features of domain patterns and show a large difference in the time‐aging stability of piezoelectric properties. For the ceramic with x = 0.03, domain patterns consist of simply one single set or a few sets of parallel stripes inside the polycrystalline grains. In contrast, for those with x = 0.065 or 0.08, herringbone‐type patterns and a large number of watermarks are additionally observed. Furthermore, the ceramic with x = 0.03 was confirmed to have a much better time‐aging stability of piezoelectric properties than the other two. The results indicate that domain structure is more stable in orthorhombic phase than in tetragonal phase.