Search

In this study, 2.0 mol% CuO-added 0.96(K0.5Na0.5)(Nb1−zSbz)O3–0.04(Bi0.5Ag0.5)ZrO3 [CKN(N1−zSz)–BAZ] piezoceramics (0.0 ≤ z ≤ 0.08) were densified at 980 °C without the secondary phase. The crystal structure of the CKN(N1−zSz)–BAZ piezoceramics changed from the tetragonal–orthorhombic structure to the tetragonal–orthorhombic–pseudocubic structure with increasing z. The CKN(N1−zSz)–BAZ piezoceramics (0.0 ≤ z ≤ 0.07) were well textured at 980 °C along the [001] direction, without holes, when 3.0 mol% Na(Nb0.9Sb0.1)O3 (NNS) templates were used. However, the specimens textured using NaNbO3 (NN) templates exhibited holes owing to the dissolution of the NN templates. Moreover, the elastic modulus and hardness of the specimen (z = 0.05) textured using the NNS template were larger than those of the specimen (z = 0.05) textured using the NN template, possibly because of the absence of holes. The [001]-textured CKN(N1−zSz)–BAZ piezoceramics exhibited a reduced dielectric constant and enhanced piezoelectric properties. Particularly, the [001]-textured CKN(N0.95S0.05)–BAZ piezoceramic provides large d33 (610 pC N−1), kp (0.68) and d33 × g33 (30 × 10−12 m2 N−1) values. A cantilever-shaped piezoelectric energy harvester was fabricated using the [001]-textured CKN(N0.95S0.05)–BAZ ceramic, which showed a large output power of 1.6 mW at the resonance frequency, indicating that this piezoceramic is a good candidate for a piezoelectric energy harvester. [ABSTRACT FROM AUTHOR]

(K0.5Na0.5)NbO3 (KNN)-based ceramics have been extensively investigated as replacements for Pb(Zr, Ti)O3-based ceramics. KNN-based ceramics exhibit an orthorhombic structure at room temperature and a rhombohedral–orthorhombic (R–O) phase transition temperature (TR–O), orthorhombic–tetragonal (O–T) phase transition temperature (TO–T), and Curie temperature of −110, 190, and 420 °C, respectively. Forming KNN-based ceramics with a multistructure that can assist in domain rotation is one technique for enhancing their piezoelectric properties. This review investigates and introduces KNN-based ceramics with various multistructures. A reactive-templated grain growth method that aligns the grains of piezoceramics in a specific orientation is another approach for improving the piezoelectric properties of KNN-modified ceramics. The piezoelectric properties of the [001]-textured KNN-based ceramics are improved because their microstructures are similar to those of the [001]-oriented single crystals. The improvement in the piezoelectric properties after [001] texturing is largely influenced by the crystal structure of the textured ceramics. In this review, [001]-textured KNN-based ceramics with different crystal structures are investigated and systematically summarized. [ABSTRACT FROM AUTHOR]