Electrical Conduction Mechanism in Bi 4 Ti 3 O 12 Single Crystal

To reveal the influence of lattice defects on electrical conduction of bismuth titanate (Bi 4 Ti 3 O 12 : BIT), one of the bismuth layer structured ferroelectrics, changes in lattice parameters and weight by high-temperature annealing and the dependence of conductivity on oxygen partial pressure ( P o 2 ) were examined for BIT powders and single crystals, respectively. Decrease in lattice parameters and weight loss by annealing suggested the bismuth vaporization and oxygen vacancy formation. The BIT single crystal showed ionic- p -type electronic mixed conduction along the a -axis and p -type conduction along the c -axis, with the conductivity along the c -axis being lower than that along the a -axis, in the P o 2 region of 1 to 3×10 -4 atm at 700°C. This indicates that oxygen vacancies are formed in the perovskite blocks leading to ionic-predominant conduction along the a -axis and low oxygen concentration in the bismuth oxide layer induces low and p -type electronic conductivity along the c -axis.