Films of molecular composites with various ratios of silanol to poly-hydroxyphenoxy-phosphazene contents have been deposited on silicon by means of the sol-gel process, annealed, then submitted to irradiations by C or Au ions. Analysis of their composition by means of various ion beam techniques and of their structure by FTIR have shown that all parts of the polymeric chains are progressively destroyed. A three-dimensional network, amorphous and highly depleted in hydrogen, is built as in the case of purely organic polymers. The chemical bonds, which are formed between silica molecules and phenyl rings during annealing treatments, are broken in the course of this radiolysis and both components segregate, as evidenced by spectroscopic ellipsometry. The spectrum of optical absorption of the carbonaceous clusters is typical of a semiconductor, contrary to that of amorphous carbon. Submicroscopic indentation tests, performed with a depth-sensing instrument, show that they are also five times harder. The internal stress in the silica network, the hardness of the mixture and its density increase in the same manner with the amount of energy deposited by ions, but they are not interdependent.