Dislocation Loops in Pressureless‐Sintered Undoped BaTiO 3 Ceramics

Dislocation loops in pressureless‐sintered undoped BaTiO 3 ceramics have been analyzed by transmission electron microscopy. The Burgers vector of the loops and its sense b =+1/2[010] were determined using the g·b =0 invisibility criteria, combined with the inside–outside contrast technique using ( g·b ) s g >0 or<0, keeping the deviation parameter s g >0. The edge‐vacancy nature was further ascertained by determining the loop habit plane normal n =[0 1 0]. Weak‐beam dark‐field imaging reveals that loops contained no stacking fault fringes; they are edge‐vacancy partial dislocation loops lying in {020} or {010} where parts of the TiO 2 or BaO layer are vacant. It is suggested that the extrinsic defects of both cations and oxygen vacancies generated by non‐stoichiometry have condensed during sintering in air and are responsible for the formation of such vacancy loops.