Fig. 1

XRD patterns of the studied samples and of a calculated cryptomelane pattern. Main panel, from top to bottom XRD patterns of MndBi10_10y, MndBi8_10y, MndBi4_10y, MndBi3_10y and a calculated cryptomelane pattern (over the 21–53 nm⁻¹ interval, CSD size of 6 nm). Patterns are scaled for clarity, as maximum intensity diffracted by δ-MnO₂ is about 3 % of the maximum intensity diffracted by cryptomelane. Arrows point out to main modulations attributable to a cryptomelane-like structure in MndBi3_10y and MndBi4_10y patterns. MndBi10_10y and MndBi8_10y patterns are overlaid in the inset at the top right to highlight that the hump at 30–33 nm⁻¹ is better defined in MndBi8_10y