Effects of annealing on particle size and pore size distribution of hydrothermally synthesized BaTiO₃ nanopowders and their grain-growth kinetics during sintering

With an increase in the annealing temperature, the hydrothermally synthesized BaTiO3 nanopowders increased in particle sizes from 100 to 260 nm and decreased in pore volume from 7.2 to 2.82 cm(3) g(-1), while the pore size remained constant at 3.06 nm. Samples with different initial particle sizes were sintered in the temperature range of 1210 degrees C-1300 degrees C and for periods of 0.5-48 h at 1270 degrees C. The kinetic grain-growth exponent of the sintered BaTiO3 samples, n, was proportional to the increase of an initial particle size and the decrease of pore volume, and the grain growth obeyed the Arrhenius equation. The activation energies for the grain growth of the sintered BaTiO3 samples with initial particle size of 100, 155 and 260 nm were 737, 702 and 755 kJ mol(-1), respectively, indicating that the activation energy was independent of the initial particle size in the range of 100-300 nm under identical purity conditions, and pore volume was supposed to be attributed to the velocity of grain growth.