Single crystals of lanthanum-substituted bismuth titanate were grown by a self-flux method, and electrical conductivities were investigated at high temperatures. Lanthanum substitution suppressed Bi vaporization during annealing and decreased the electrical conductivity in both the a- and c-axes. It is suggested that lanthanum substitution stabilizes the perovskite blocks and hence decreases the concentrations of oxygen vacancies and holes as the conduction carriers. An ab-initio calculation indicated that the formation energy of an oxygen vacancy in the perovskite block is increased by lanthanum substitution, supporting the above experimental results.

Keywords: bismuth titanate, lanthanum substitution, single crystal, Ab initio calculation, oxygen vacancy