Structure and microstructure of the metastable B phase (NiAl10O16): I. Preparation and structural study by X-ray diffraction

The B phase of composition NiAl₁₀O₁₆ is one of the metastable phases found in the Al₂O₃NiO system. Twinned crystals of B were prepared by annealing samples at 1150°C. Indexing the crystal diffraction patterns with 12 twin variants was done. A structural model belonging to the space group $\text{P2}{}_1\text{b}$ is proposed. The B phase has a periodic antiphase boundary (PAPB) structure based on the (100) spinel planes with an antiphase vector R = $\text{1}\text{4}\text{1}\text{1}\text{0]}$. Moreover this structure is slightly modified by introducing periodic steps on PAPB planes. These steps give rise to a particular order of cation vacancies.