Figure 4.

(a) SEM and (b–h) STEM micrographs of SrTiO₃/Bi₄Ti₃O₁₂ heterostructural platelets (mainly edge-on-oriented platelets, which were thinned to electron transparency) as obtained after 1 h of a reaction at 200 °C (6 M NaOH, Sr/Ti = 12). (b) DF and (c) BF images showing (mainly) edge-on platelets along the whole side length; (d) DF of the central part of the platelet (showing SrTiO₃ layers and partially disintegrated Bi₄Ti₃O₁₂ inside the groove). (e) HR image of the area marked in (d) showing the disintegration of Bi₄Ti₃O₁₂. (f) Another DF of the part between the central area and the edge of the platelet. (g) Magnified area from the image (f) presenting dissolution of Bi₄Ti₃O₁₂ and as-formed SrTiO₃ with the incorporated Bi-rich layer (HR image of this part is in the inset). (h) DF image of the edge of the platelet with two parallel SrTiO₃ platelets with incorporated Bi-rich layers. (i) Schematically shown processes of the TC reaction from Bi₄Ti₃O₁₂ to SrTiO₃ as reconstructed from STEM results, presented in (b)–(h).