The crystalline properties of silica biomorphs vary within and between morphologies (2508.21149v1)

Abstract: Silica-carbonate biomorphs are a class of emergent materials, i.e. composite microstructures made of nanometric carbonate crystallites surrounded by amorphous silica. They form via a co-precipitation process in an interplay between alkaline earth metal carbonate and siliceous species, and self-organize into a multitude of shapes with a distinct long-range order of the carbonate nanocrystals. Biomorphs are frequently studied to understand the formation of life-like structures emerging from geochemical processes at extreme conditions. Further, due to their optical properties they lend themselves as a platform for optical, electronic or magnetic functionalization. A big hurdle in this task is our incomplete understanding of the underlying formation process and how the interplay between synthesis parameters affects important nanoscale properties such as crystalline structure and texture, as well as the shape on the microscale. Here, we use X-ray texture and diffraction tomography to unveil the local crystalline texture in 3D of silica-witherite biomorphs. We find surprisingly different growth motifs across different morphologies, but also that the crystalline properties vary significantly within a single structure. We distinguish different growth regimes and from that, infer how the co-precipitating silica shapes the crystalline particles. Thereby, we gain deeper insight into how biomorphs form these distinct complex morphologies.