Synthesis of anisotropic NaNbO_3 seed crystals and fabrication of textured (K_(0.5)Na_(0.5))NbO_3-based ceramics

摘要

High aspect ratio patelike NaNbO_3 particles with pure perovskite structure have been successfully synthesized by topochemical microcrystal conversion (TMC) from plate-like precursor particles of the layer-structured Bi_(2.5)Na_(3.5)Nb_5O_(18). By changing the Bi_(2.5)Na_(3.5)Nb_5O_(18)/Na_2 CO_3 ratio, large and thin NaNbO_3 particles with a thickness of approximately 0.5 μm and a width of approximately 20 μmwere obtained. The obtained NaNbO_3 particles is quite suitable for fabricating textured (K_(0.5)Na_(0.5))NbO_3-based ceramics. Using the fine platelike NaNbO_3 particles as templates, dense <001> -oriented (K_(0.5)Na_(0.5))NbO_3-0.5 mol %MnO_2 ceramics with high texture quality (Lot-gering factor F_(001) = 87 %) and excellent piezoelectric properties were produced by templated grain growth. Compared with randomly oriented ceramics, textured samples show greatly enhanced properties. The room-temperature strain S, the piezoelectric coefficient d_(33)~* and d_(33) reach up to 0.093 %, 233 pm/V and 195pC/N, respectively, which are all about 1.5 times larger than those of non-textured ceramics.