Piezoelectric ceramics can convert mechanical stress or pressure into an electrical charge and vice versa, and are therefore the cornerstone in several modern technologies, for example medical ultrasound imaging. There is a general need to optimize performance and develop new, lead-free compositions, and utilizing the optimized grain orientation is one route. Piezoelectric ceramics can reach properties close to those of single crystals if they consist of aligned grains (texture). Compared to a bulk ceramic made by uniaxially pressed and sintered powder, the texture process requires processing with shear forces that align anisometric template particles seeding directional grain growth.

I will present how this texture is achieved in lead-free K_0.5Na_0.5NbO₃-based systems with different template particle geometries, and the effect of the resulting texture on the piezo-, ferro- and dielectric properties. Furthermore, I will discuss considerations for the crystallographic direction of the texture. By designing a material composition with higher phase stability than BaTiO₃, Ba_0.92Ca_0.08TiO₃, I will present how [100] crystallographic type texture increases the piezoelectric response, while [111] type texture decreases it, and how this is in accordance with predictions from rotator/extender ferroelectricity behavior.       

In addition to investigate texture in bulk ceramics to replace single crystals, it is interesting to introduce texture to ceramics already made by shaping techniques with shear forces, such that texture can improve them without significant extra processing steps. One such process is tape casting of thin and multilayered piezoelectrics, e.g. for multilayer actuators, capacitors or for high frequency ultrasound transducers. I will present results on tape casting of thick films of (Li_0.06(K_0.52Na_0.48)_0.94)(Nb_0.71Ta_0.29)O₃ doped with 0.25 mol% Mn (KNNLTM). KNNLTM is a promising lead-free composition for ultrasound transducers, due to its high coupling coefficients as a single crystal. Increased coupling coefficients (k_t) in textured compared to random ceramics, and multilayers for high-frequency ultrasound transduction with a thin, dense, piezoelectric active KNNLTM layer supported on a porous KNNLTM backing could be obtained.