High-resolution electron microscopy and X-ray diffraction study of intergrowth structures in α-and β-type YbAlB₄ single crystals

Structural features of layered boride YbAlB₄ single crystals with YCrB₄-type (α-type) and ThMoB₄-type (β-type) phases derived from a hexagonal AlB₂-type structure were investigated by electron diffraction, high-resolution electron microscopy and X-ray diffraction. X-ray diffraction experiments indicate the existence of some structural motifs. High-resolution images clearly show that the structural motifs build the intergrown lamellar structures in the matrix. The lamellar structures can be characterized by a coherent tiling of deformed Yb hexagons, which are a common structure unit in the α-and β-type structures. The characteristic intergrown nanostructure is similar to that observed in the β-type TmAlB₄ polycrystalline sample.