To unfault a 1/3[1010](1010) dislocation loop in alumina, we must propagate a 1/3 [0001] partial shear dislocation across the loop plane.17 This is described by the following dislocation reaction:

1[10l0] + ±[0001] ! i[10T1] (prismatic) [9

faulted loop partial shear unfaulted loop

This reaction is symmetric with that shown in eqn [8] for unfaulting a (0001) basal loop in alumina. The reaction in eqn [9] is shown graphically in Figure 4.

When we pass a 1/3 [0001] shear through a 1/3[1010](1010) dislocation loop, the cation planes beneath the loop assume new registries such that in eqn [6], ajpj and a2p2 commute as follows: a1p1 ! a2p2 ! a1p1. The anion layers beneath the loop are left unchanged (B! B, C! C). In addition, the Al-only cation layers are unchanged (p0 ! p0). Taking the faulted (0001) stacking sequence in eqn [2] and assuming that the planes to the right
are above the ones on the left, we perform the 1/3 [0001] partial shear operation as follows:

(P’S («AC) (P’S) (a.$2C) (P’S) (a, p,C) |(P’g|(a, frC) (P’S) (oftC) (faulted)

(a2P2C) (P’S) (a, p,C)

(P’S (a, P,C) (P’S («2P2C) (P’S (a, p,C) (P’S (012P2C) (P’S) (a, p,C) (unfaulted)

[10]

After propagating the partial shear through the loop, we are left with an unfaulted layer stacking sequence. The resultant dislocation loop, 1/3 [1011], is a perfect dislo­cation. The resultant 1/3 [1011] (0001) dislocation is a mixed dislocation, in the sense that the Burgers vector is canted (not normal) relative to the plane of the loop.