Ferroelectric Properties of Substituted Aurivillius Phases SrBi2Nb2-xMxO9 (M=Cr, Mo)

摘要

Partially doped Aurivillius phases SrBi2Nb2-xMxO9 (M=Cr and Mo) were successfully synthesized and characterized. The extent of the substitution was limited at ~20 mole % because of the size differences between Nb5+ and Cr6+ , and between Nb5+ and Mo6+ . When the amount of substitution exceeded ~20 mole%, the phases began to collapse and the second phases were made. The dielectric constants of substituted compounds were enlarged nevertheless Cr or Mo is substituted. The increment is bigger in the Mo substituted compound than in the Cr doped one although the Nb(Cr)O6 octahedra could be more strongly distorted than the Nb(Mo)O6 octahedra since the ionic size difference between Nb5+ and of Cr6+ is much bigger than that between Nb5+ and Mo6+ . Consequently, the dielectric constant of the substituted Aurivillius phase Bi2An-1Bn-xMxO3n+1 depends on the extent of distortion of the BO6 octahedra and more strongly on the polarizability of the metal.