The measured in-and ex-situ SAXS data were fitted by McSAS v. 1.3 software 41 under the simplified assumption that the pores could be modelled as hard spheres . A mutual interference of the developing pores is assumed to occur in agreement with other SAXS studies of phosphate materials . Considering this and other factors, the hard sphere model output the most meaningful and accurate fitting data. A full evaluation of the fitting model can be found in the ESI. WAXS was used to monitor crystalline-to-amorphous transitions. The hard sphere structure factor can be described by the Percus-Yevick structure factor :