Characterization of Internal Pores in Hydrothermally Synthesized BaTiO3 Particle by Transmission Electron Microscopy

Hydrothermally synthesized barium titanate, BaTiO₃ (commercially available), has internal pores in small particles. The three-dimensional structures of the pores were successfully observed using transmission electron microscopy (TEM) and reconstructed by a tomography system. The behavior of the internal pore is observed in situ with increasing temperature on the thermal stage of a TEM device. We succeed in recording the movement of pores and small grains. At >1128 K, some pores move out from the particle's surface during TEM observation. The temperature roughly agrees with the temperature at which the density of BaTiO₃ powder sharply increases. During observation with increasing temperature, a thin layer appeared on the particle's surface at >73 K and then disappeared at 1193 K.