The full width half maximum (FWHM) values of the XRD peaks for the m = 5 phase increase as Ti concentration decreases across Series 4 (see Table ). While particle size effects could contribute to peak broadening, the consistent deposition method applied throughout the series should limit significant variations in film thickness and grain size. Additionally, XRD pattern modeling (see Supplementary Information Section SI3) indicates that no single crystallite size can fully account for the broadening observed in all reflections, as the peaks widen independently of crystal size. Increased structural stacking disorder, such as stacking faults, OPB defects and small regions of phases with different m values (evident in the TEM data in Fig. ), almost certainly contributes to the broadening of the XRD peaks, which is reflected in the FWHM values. The increase in peak broadening for the m = 5 phase implies a more disordered periodic structure as x values decrease. Furthermore, peak broadening for the m = 6 phase is over twice that of the m = 5 reflections at the same 2 theta value, indicating that the m = 6 phase is more defective than the m = 5 phase.