Numerical simulations of reactive cold sintering of BaTiO3

Numerical simulations of reactive cold sintering of BaTiO3 are performed under the experimental condition of Guo et al. It is suggested that amorphous BaTiO3 particles are produced first by chemical reactions and subsequent nucleation from the aqueous solution according to the Ostwald's rule of stages. For the case of cold sintering under 300 degrees C and 500 MPa, the amorphous particles are transformed into crystalline particles partly during the initial heating stage by a simple thermal excitation when the particle size is less than about 5 nm and partly during cold sintering under high pressure through coalescence with other crystalline particles. For the case of 150 degrees C in sintering temperature, on the other hand, appreciable amounts of amorphous particles remain even after the cold sintering due to the incomplete sintering. The calculated grain sizes almost agree with the experimental data, which supports the present numerical simulations.