Mechanism of Bi0.5Na0.5TiO3 and Bi4.5Na0.5Ti4O15 template synthesis during topochemical microcrystal conversion and texturing of Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics

The mechanism by which Bi0.5Na0.5TiO3 and Bi4.5Na0.5Ti4O15 templates are synthesized via a topochemical microcrystal conversion method using Bi4Ti3O12 precursor and TiO2 particles was investigated based on their crystal structures. The Bi0.5Na0.5TiO3 template consisted of a mixture of plate-like and equiaxed particles, whereas the Bi4.5Na0.5Ti4O15 template consisted only of plate-like particles. The size of the plate-like and equiaxed particles was dependent on the size of the Bi4Ti3O12 precursor and TiO2 particles, respectively. The Lotgering factor and piezoelectric constant of textured Bi0.5(Na0.8K0.2)0.5TiO3 ceramics prepared using the Bi0.5Na0.5TiO3 template were lower than those of the textured Bi0.5(Na0.8K0.2)0.5TiO3 ceramics prepared from the Bi4.5Na0.5Ti4O15 template. This can be attributed to the small amount of plate-like particles in the Bi0.5Na0.5TiO3 template caused by the inevitable co-existence of equiaxed particles.