The synthesis of ZrP(PP)x by direct precipitation allowed compounds with x ranging from 0.13 to 1.54 to be obtained.In order to better highlight the relationship between the initial amount of phosphonic acid in solution and that found in the final product, the PP molar fraction in the solids, having composition Zr(O3PC6H5)x(O3POH)1.95‑x(OH)0.1, was calculated according to the formula: