GRAIN-ORIENTED CERAMICS IN BISMUTH LAYER-STRUCTURE COMPOUNDS FOR CAPACITOR MATERIAL

The systematic investigation of the composition of high-permittivity b ismuth layer-structure oxides and the examination of the grain-oriente d ceramics were carried out. Through investigation of the composition of high-permittivity materials, it was clarified that the dielectric c onstant epsilon(s) of more than 1000 can be attained using Pb4Bi4Ti7O2 4 compound. Moreover, it was confirmed that favorable characteristics for use as dielectric ceramics for high-voltage capacitors (stability of epsilon(s) on DC bias, high resistivity, etc.) can be attained usin g this compound. The examination of the characteristics of grain-orien ted Pb4Bi4Ti7O24 ceramics clarified that the dielectric breakdown stre ngth and the stability of epsilon(s) on DC bias can be improved in the direction perpendicular to the polarization axis. As a result, grain- oriented ceramics are considered to be appropriate for use as capacito r materials.