Figure 3. Switching metallic-type properties of charged domain walls.

(a) Current–temperature dependence shows switching of the metallic-type conductivity when a 90° head-to-head (H–H) charged domain wall is created and annihilated at PTs. The domain walls formed in tetragonal BaTiO₃ cannot exist in the orthorhombic and paraelectric phases as illustrated in the cartoon. The charged domain wall is annihilated at both transitions from the tetragonal phase. The annihilation at the transition to the paraelectric phase is permanent in this case. The conductivity characteristic shows change from metallic-type temperature dependence and magnitude to thermally activated conduction typical for wide-bandgap semiconductor bulk BaTiO₃. (b) Linear-scale current–temperature dependence showing pronounced positive temperature coefficient indicating thermally non-activated (that is, metallic-type) conduction at domain walls as illustrated in c.