Mechanism for the Sidewise Motion of 180° Domain Walls in Barium Titanate

An important unanswered question concerning the sidewise motion of 180° domain walls in single crystal BaTi${\mathrm{O}}_3$ is the mechanism by which the boundaries move. This paper considers two possible models. One model assumes that the wall motion results from the repeated nucleation of steps along existing parent 180° domain walls and that the nucleation rate is the controlling factor in the propagation of the wall. The second model investigated involves paired screw dislocations of opposite sense which propagate the wall in a manner analogous to certain types of crystal growth.