BaBi_4Ti_4O_<15>単結晶の電気的異方性

概要

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Electrical anisotropy of dielectric and DC/AC conduct ing properties of single crystals of barium bismuth titanate (BaBi_4Ti_4O_<15>) , which is a member of bismuth layer structured ferroelectrics, has been studied and compared with those of polycrystalline samples. It was found that BaBi_4Ti_4O_<15>, when measured at 1 MHz, showed about 6 times and 58 times higher dielectric permittivity in the direction parallel to bismuth layer (crystallographic a (b) axis) than those in the perpen dicular direction (c axis) at room temperature and the Curie temperature, respectively. DC/AC conductivity showed a higher value in the direction parallel to the bismuth layer than those in the perpendicular direc tion. On the other hand, the activation energy for elec tric conduction in the direction parallel to the bismuth layer showed a lower value. Polycrystalline samples had intermediate properties of those of the two direc tions in single crystals. Complex impedance measure ments also showed anisotropy in the dielectric and the DC conducting properties even for paraelectric phase. Thus, the bismuth layer was thought to act as an in sulating and paraelectric layer in BaBi_4Ti_4O_<15>
社団法人日本セラミックス協会の論文
1994-08-01