Deformed microstructure in pressureless-sintered barium titanate

The sintered microstructure of pressureless-sintered BaTiO3 analysed by transmission electron microscopy (TEM) reveals that plastic deformation occurred at 1400 °C when the slip systems of 〈1 1̄ 0〉{1 1 0}, 〈1 0 0〉{1 1 0} and 〈100〉{0 0 1} were activated by the intrinsic sintering stress (Σ). Dislocations with the Burgers vectors b1=〈110〉 and b1′=〈100〉 have dissociated. The dissociation reactions of b1=b2+b3 are: [1 0 1] → [0 0 1] + [1 0 0] and [0 0 1] → 12[1 0 1] + 12[1̄ 0 1], respectively. Both dissociated dislocations contained a series of scallop-shaped half-loop partials with the Burgers vectors respectively of b3=[100] and b3′=12[1̄01]. The dissociations took place by a climb mechanism. Polygonisation in dynamic recovery, necessitating both glide and climb of dislocations, occurred during sintering at 1400 °C, and which is clearly evidenced by sub-grain formation. Densification was contributed by dislocation mechanisms where the ceramic has been plastically deformed by the sintering stress. Densification of the undoped and Sr-doped BaTiO3 compositions by pressureless-sintering in relation to the dislocation substructure is discussed.