Universality of Conductance Peak in Ferroeletric Phase Transition: Impurity Doped BaTiO₃and (Pb(Zn_1/3Nb_2/3)O₃)_0.92(PbTiO₃)_0.08Single Crystals

The temperature (T) dependence of the quasi-equilibrium conductivity (T) of iron-doped, oxygen-reduced, and undoped BaTiO 3 single crystals and relaxor (Pb(Zn 1 /3 Nb 2/3 )O 3 ) 0.92 (PbTiO 3 ) 0.08 (PZNT-PT) crystals is measured. We have found that all the σ-T's exhibit the peaking at Curie temperature as far as the conductance in the paraelectric phase is sufficiently low. The value of the σ peaks of BaTiO 3 single crystals is approx. 1 nΩ− 1cm− 1 and is independent of impurities, whereas σ of the paraelectric phase depends on impurities. We speculate that the conductance peaking at phase transitions is a general property of ferroelectrics.