Rheological characterization of the BaTiO3 sol–gel transition
BaTiO3 gels have been prepared by hydrolysis and polycondensation reactions between titanium isopropoxide and barium hydroxide in the presence of methoxyethanol, methanol and water. The rheology of the sol–gel transition was studied with a rheometer allowing low-amplitude sinusoidal oscillations. Experimental data show a continuous increase in the complex viscosity with time, showing the progressive character of the transition. Different growth models and the percolation theory are used for characterization of the system. These models suggest that the gelification process first produces spherical particles (mass fractals) and that these spherical particles then agglomerate to form a three-dimensional network responsible for the observed enthalpic elasticity deduced from the equations of percolation.