RHEOLOGICAL CHARACTERIZATION OF THE BATIO3 SOL-GEL TRANSITION

BaTiO3 gels have been prepared by hydrolysis and polycondensation reac tions between titanium isopropoxide and barium hydroxide in the presen ce of methoxyethanol, methanol and water. The rheology of the sol-gel transition was studied with a rheometer allowing low-amplitude sinusoi dal 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 use d for characterization of the system. These models suggest that the ge lification process first produces spherical particles (mass fractals) and that these spherical particles then agglomerate to form a three-di mensional network responsible for the observed enthalpic elasticity de duced from the equations of percolation.