Crystallographic Orientation Analysis on Calcium Cobaltite Ceramic Grains Textured by Reactive‐Templated Grain Growth

Textured thermoelectric [Ca ₂ CoO ₃ ] _0.62 [CoO ₂ ] (denoted as CCO) ceramic was fabricated and distributions of crystallographic orientations for local grains and misorientation angles between grains were investigated by electron backscatter diffraction pattern analysis. Most of the grains are preferentially aligned with their conductive ab ‐planes parallel to the original tape‐casting surface. Parallel aligned boundaries are observed in a single grain and the nearest neighboring crystallites sharing these boundaries have misorientation angles of multiples of 60°. It is suggested that these unique domain structures are formed during the topotactic nucleation and growth of monoclinic CCO phase on its precursor Ca _x CoO ₂ in a hexagonal crystal system.