Direct selective laser sintering of hexagonal barium titanate ceramics

A direct selective laser sintering (SLS) process was combined with a laser preheating procedure to decrease the temperature gradient and thermal stress, which was demonstrated as a promising approach for additive manufacturing of BaTiO3 ceramics. The phase compositions in BaTiO3 ceramics fabricated by SLS were investigated by X-ray and neutron diffractions. The surface morphologies and cross-section microstructures were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A dense hexagonal h-BaTiO3 layer was formed on the surface and extended to a depth of 500 mu m, with a relative density higher than 97% and absence of pores or microcracks. SLS resulted in the formation of the high-temperature phase, h-BaTiO3, which was retained at room temperature possibly due to the high cooling rate. The grain boundaries of SLSed h-BaTiO3 ceramics consist of a Ti-rich secondary phase. Compared with that of the pressureless sintered t-BaTiO3 ceramics, the Vickers hardness of SLSed h-BaTiO3 is 70% higher.