Impact Of Surface Roughness On Recrystallization Of An Alpha-Al2o3(001) Single Crystal To Alpha-Alo(Oh) Diaspore Microcrystals

We demonstrate that the surface of an alpha-Al2O3(001) single crystal recrystallizes to alpha-AlO(OH) under ultrahigh pressure (8 GPa) at 600 degrees C. The recrystallization depends on the degree of surface roughness. A polished surface topotaxially recrystallizes to (100)-oriented alpha-AlO(OH) microcrystals, while unpolished surface recrystallizes to polycrystalline alpha-AlO(OH). This study demonstrates a new synthetic route to obtain oriented crystals of ultrahigh-pressure-phase materials and paves the way for the investigations of the physical and chemical properties of such materials.