Surface modification of pre-sintered BaTiO3 particles

Generally, the surface properties of powder particles strongly influence the sintering behavior of the resulting compacts. This paper describes the surface modification of pre-sintered BaTiO3 particles (5–10 μm in size) by leaching under different hydrothermal conditions (leaching medium, time and temperature). These modifications enable to control the thickness and the degree of crystallinity of the resulting TiO2-rich surface layer on the BaTiO3 particles. A hydrothermal treatment for 1 h at 100 °C in 0.1 M acetic acid results in the formation of an amorphous, TiO2-rich, and 5 nm thick surface layer as revealed by high-resolution electron microscopy and electron energy loss spectroscopy. Microwave radiation was found to have no significant influence on the leaching processes under the conditions used here. Modified surface layers improve the densification behavior of the BaTiO3 particles, but are insufficient to promote the evolution of a completely dense microstructure of the ceramics. A further improvement in densification and the formation of grain boundaries free of pores and with a high electrical conductivity can be achieved by hot isostatic pressing.