Grain-oriented fabrication of bismuth titanate ceramics and its electrical properties

The concept of grain-oriented fabrication in ceramics, which utilizes anisotropy either in morphology or some specific property of the particle, is reviewed. A fabrication method, which maximizes the grain orientation, is described for Bi/sub 4/Ti/sub 3/O/sub 12/. The process utilized plate-like morphology of Bi/sub 4/Ti/sub 3/O/sub 12/ particles and yielded a ceramic with an X-ray density of 95.4% and an unprecedented value of 100% for Lotgering's orientation factor in the direction of orientation. The dielectric and piezoelectric properties of this ceramic are described and compared to single crystal values. Complex impedance analysis of the ceramics was used to explain the dielectric relaxations at elevated temperatures. The use of grain-oriented fabrication as a practical technique for making polycrystalline ceramics with electrical properties close to those of single crystals (in the direction of orientation) is emphasized. The use of grain-oriented Bi/sub 4/Ti/sub 3/O/sub 12/ ceramics as a high-temperature piezoelectric transducer is suggested.<
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