The dielectric and piezoelectric properties of MBi/sub 4/Ti/sub 4/O/sub 15/ (M=Sr, Sr/sub 0.5/Ca/sub 0.5/, Ca) ceramics

We have investigated the crystalline structure, dielectric, ferroelectric and piezoelectric properties of the MBi/sub 4/Ti/sub 4/O/sub 15/ (M=Sr, Ca, Sr/sub 0.5/Ca/sub 0.5/) ceramics. The remanent polarization(P/sub r/) of SrBi/sub 4/Ti/sub 4/O/sub 15/(SBT) and CaB/sub 14/Ti/sub 4/O/sub 15/(CBT) ceramics was 2.2 /spl mu/C/cm/sup 2/ and 0.3 /spl mu/C/cm/sup 2/, respectively. The k/sub t/ of SBT and CBT OF ceramics exhibited a low value(<4%) compared to that of PZT(60%), but Q/sub m/ displayed a large value(>2000) compared to that of PZT(1000). The changes of dielectric, ferroelectric and piezoelectric properties in these ceramics have been originated from the lattice distortion of BO/sub 6/ oxygen octahedra according to the size of ion radius into A site which are represented from (Bi/sub 2/O/sub 2/)/sup 2+/(A/sub n-1/B/sub n/O/sub 3n+1/)/sup 2+/ in the bismuth layered structure.