Spray drying granulation of potassium sodium niobate (KNN) for binder jetting: Feedstock preparation and influence on sintered material properties

Binder jetting of potassium sodium niobate (K0.5Na0.5NbO3) offers potential for generating shape-dependent responses with high industrial output. However, the printing stage relies heavily on the properties of the dry feedstock, making its performance optimization crucial. In this regard, morphological functionalization through granulation can be a useful methodology. This study characterizes two powders in dry and wet states to develop colloidal suspensions for spray drying granulation. Particle size, shape, and ζ-potential are measured to stabilize them in an aqueous slurry. Granule morphology and flowability are assessed and compared with the original feedstock. Disk-shaped specimens are then printed and sintered. Spray drying granulation successfully produces spherical and fine feedstocks compatible with the typical layer thickness (50 μm) of binder jetting. Densified parts displayed significant residual porosity (20–40 %) along the building direction, affecting piezoelectric performance: strain coefficients were reduced, but increased voltage coefficients yielded high figures-of-merit.