Oriented and ultrafine-grain potassium sodium niobate piezoelectric ceramics prepared by heterogeneous microcrystalline transformation

The rapid growth of platelet templates with a large volume results in poor density and repeatability for textured Na0.5K0.5NbO3 (KNN) ceramics. To synthesize needle-like templates with small volume, a heterogeneous microcrystalline transformation method was proposed. Acicular heterogeneous microcrystalline were synthesized from the precursor with tungsten bronze structure. The experimental results suggested that the perovskite phase on the surface of these particles could undergo epitaxial growth and complete texture evolution in the matrix. Dense textured KNN ceramics were prepared by templated grain growth method using the obtained heterogeneous microcrystalline as templates. In addition, the KNN nano-powder was synthesized with a high crystallinity when the precursor was completely transformed, which was an ideal raw material for the preparation of ultrafine-grain KNN ceramics. This work provides a new way for the preparation and microstructure control of high-performance lead-free piezoelectric ceramics.