Silicate hybrid materials were prepared by the sol-gel process with the addition of x wt% of zirconium propoxide (x = 0 and 1). The thermal behavior as well as the influence of Zr addition was studied by thermal gravimetric analysis and differential thermal analysis. The microstructure evolution with temperature was investigated by X-ray diffraction and small angle neutron scattering. It was found that the beginning of polymer degradation occurs at a higher temperature in the material prepared with addition of Zr than in the one prepared without. At the nanometric scale, the materials prepared without Zr show smooth interfaces, whereas those with Zr present a mass fractal structure. This structure is also observed in the material without Zr after thermal treatment at 200 C. The results showed that bioactivity is favored by mass fractal structures in comparison with one consisting of smooth surfaces.