Nano-BaTiO3 phase transition behavior in coated BaTiO3-based dielectric ceramics

In this work, the phase structure of BaTiO3 nanopowders produced by the alkoxide-hydroxide and the hydrothermal method, respectively, was systemically investigated. BaTiO3 nanopowders with cubic phase produced by the alkoxide-hydroxide method could transform to tetragonal phase when heated to about 1100 °C. Cubic to tetragonal phase transformation behavior of BaTiO3 nanopowders coated with 0.3BZT-0.7BT or 0.03Nb2O5-0.01Co2O3 was studied. The internal stress within core-shell structure was proposed to explain the BaTiO3 phase transformation behaviors. The mismatch of thermal expansion coefficient between core and shell plays a crucial role in cubic to tetragonal phase transformation of BaTiO3. By tuning the composition of shell and the ratio of the shell to the core, the cubic BaTiO3 core can transform to tetragonal phase successfully after sintering at 1100 °C in BaTiO3 based ceramics with core-shell structure and it is mainly resulted by the reduced internal stress between the shell and core.