## 3 Results and Discussion
The resulting products exhibited consistent composition, irrespective of whether the starting granules contained magnesium salts or were synthesized using Mg-containing or Mg-free solutions. In order to ascertain the structural parameters of the synthesized single-phase PR1/48h-PR3/48h samples, a Le Bail refinement of the XRD data was conducted. The XRD patterns, together with the fitting curves derived from the Le Bail refinement, are displayed in Figure 3. The Le Bail refinement plots demonstrate an excellent correlation between the observed XRD patterns (red circles) and the calculated patterns (black lines), which correspond to the allowed Bragg reflections (green ticks), while the discrepancy between the experimental and refined data is shown by the blue line. This confirms the successful formation of the Mg-WH phase with a rhombohedral structure and space group R3c. The structural parameters of the Mg-WH phase synthesized from various starting compositions of raw granules during the 48 h synthesis process are presented in Table 1. The resulting products exhibited consistent structural characteristics, both within the set of samples and when compared to previously published data [24]. \begin{table}
\begin{tabular}{c c c c} \hline
**Sample** & **PR1/48h** & **PR2/48h** & **PR3/48h** \\ \hline \(a\), Å & 10.38042 (44) & 10.36717 (46) & 10.33965 (92) \\ \(c\), Å & 37.1445 (17) & 37.1087 (17) & 37.1038 (35) \\ Cell volume, Å\({}^{3}\) & 3466.21 (26) & 3454.04 (27) & 3435.27 (54) \\ R\({}_{\rm p}\) & 2.01 & 1.82 & 1.72 \\ R\({}_{\rm wp}\) & 2.68 & 2.38 & 2.19 \\ \(\chi^{2}\) & 1.74 & 1.39 & 1.19 \\ Crystallite size, nm & 46 & 52 & 17 \\ \hline \end{tabular}
\end{table} 
Table 1: Structural, R-values, \(\chi^{2}\), and microstructural data elucidated from XRD for PR1/48h, PR2/48h, and PR3/48h samples. Figure 3: XRD patterns with the fitting curve by Le Bail refinement of the synthesized PR1/48h (**a**), PR2/48h (**b**), and PR3/48h (**c**) granules. The granules synthesized by a dissolution-precipitation reaction were subjected to analysis by FTIR spectroscopy. Figure 4a-c illustrates the FTIR spectra of the materials obtained under varying conditions, with a particular emphasis on the 1350-400 cm\({}^{-1}\) region to elucidate the distinctive functional groups present in the synthesized granules. The FTIR spectra of the R1-R3 raw granules (see Figure 4a) display absorption bands centered at 1110 cm\({}^{-1}\), 669 cm\({}^{-1}\), and 598 cm\({}^{-1}\), which are attributed to the stretching and bending modes of the sulfate (SO4\({}^{2-}\)) ion [25]. A weak absorption band centered at 869 cm\({}^{-1}\) is attributed to the stretching vibration of hydrogen phosphate (P-O(H)) groups, originating from the precursor salts (NH4)2 HPO4 and MgHPO4.3H2O. The FTIR spectra of the granules PR1/24h-PR3/24h (Figure 4b) display the presence of absorption bands corresponding to PO4\({}^{3-}\) and HPO4\({}^{2-}\) functional groups. The absence of SO4\({}^{2-}\)-related absorption bands suggests that the sulphate-containing precursors were completely dissolved and subsequently transformed into CP materials during the 24 h synthesis process. These findings are corroborated by the XRD analysis, which identified specific CP phases: the PR1/24h sample exhibited the presence of CDHA and Mg-WH; the PR2/24h and PR3/24h samples displayed the presence of DCPA and Mg-WH phases (see Figure 2b). The observed absorption bands at 1180 cm\({}^{-1}\), 1065 cm\({}^{-1}\), 1011 cm\({}^{-1}\), and 954 cm\({}^{-1}\) are attributed to the P-O and P-O(H) stretching vibrations associated with the PO4\({}^{3-}\) and HPO4\({}^{2-}\) groups, which are integral to the crystal structures of the CDHA, DCPA, and Mg-WH phases, are present to different extents in the synthesized granules. The differences in the intensity of the absorption band at 1065 cm\({}^{-1}\) between the PR1/24h and PR2/24h samples provide further insight into the phase composition.