Impedance and ionic conduction of single crystalline BaTi₂O₅

Electrical properties of single-crystalline BaTi₂O₅, prepared by a floating zone method, were examined by AC impedance spectroscopy at frequencies of 10⁻² to 10⁶ Hz at temperatures of 425–970 K. Complex impedance in a direction perpendicular to (001) was exhibited by a single resistor (R)–capacitor (C) parallel circuit. In the direction perpendicular to (010), four R–C parallel circuits were involved: two R–C circuits were associated with a strong temperature-dependent ferroelectric response and a slightly temperature-dependent paraelectric response, while the other two R–C circuits corresponded to the interface phenomena associated with ionic conduction. The electrical conductivity in the direction perpendicular to (010) was one-to-three orders of magnitude higher than that in the direction perpendicular to (001).