Stacking faults and stacking fault energy of hexagonal barium titanate

Stacking faults in hot-pressed hexagonal BaTiO3 (the 6H-polytype) ceramic have been analyzed adopting the 2 pi g.R-F=0 (or 2n pi) invisibility criteria, and dislocations were examined by the g.b=0 effective invisibility criteria, both using transmission electron microscopy. Perfect basal dislocations with b(B) = 1/3 <(1) over bar2 (1) over bar0 > have dissociated into pairs of prism-plane half-partials with b(Pr) = 1/3 < 01 (1) over bar0 > by glide in the (0002) fault plane of an alpha-type extended planar stacking fault. Consequently, planar fault F-A divided by half-partials was segmented into the initially faulted regions (F-A1, F-A3, F-A5) of extended planar stacking faults and the complex-faulted regions (F-A2, F-A4) of complex extrinsic stacking faults superposed by the stacking fault ribbon created by half-partials. High-resolution imaging enables unambiguous differentiation of stacking sequence for all fault segments parted by half-partials. Change of the stacking sequence across half-partials reveals the atomic configurations of the faulted regions and the shear directions along < 01 (1) over bar0 > in (0002). The stacking fault energy of h-BaTiO3 derived from the separation between half-partials is compared with data from the literature. The discrepancy is attributed to non-equilibrium configuration and to the stacking sequence altered in the faulted regions embedded with half-partials.