Masakazu Hirose

Piezoelectric Properties of SrBi4Ti4O15-Based Ceramics

Piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT) based ceramics, were studied. By means of La substitution and Mn addition, the maximum value of Q (Qmax ) between resonant frequency and anti-resonant frequency was larger than that of SBT. These materials could be utilized in practical applications as substitutes for lead titanate based ceramics (PT) and lead zirconate titanate based ceramics (PZT) which are used mainly in resonators. The reason for the higher Qmax value was identified by microstructual analysis as being due to the absence of a defect structure.

Piezoelectric Properties of Bi3TiNbO9-BaBi2Nb2O9 Ceramics.

Piezoelectric properties of lead-free bismuth layer structure oxides, (1-x)Bi3TiNbO9 (BTN)–xBaBi2Nb2O9 (BBN) (m=2) ceramics, have been studied. We have observed large piezoelectric properties for x values between 0.1 and 0.3. Within this range of x values, these specimens have an orthorhombic structure, high anisotropy of the a and b axes and high resistivity. Also, for these samples, a large coercive force (Ec) of 8.0 kV/mm, large remanent polarization (Pr) of 7.1 µC/cm2 at 200°C and high Curie temperatures (Tc) of 700–900°C have been obtained. Maximum mechanical quality factor (Qm) of 9000 at 16 MHz thickness extensional third vibration mode (TE3rd) has been measured.

Thickness-Shear Vibration Mode Characteristics of SrBi4Ti4O15-Based Ceramics

Dielectric and piezoelectric properties have been investigated in bismuth layer-structure compounds SrBi4Ti4O15 (SBT) and BaBi4Ti4O15 (BBT)-based solid solutions. Lanthanum-substituted and manganese-added SBT and BBT form solid solutions for all levels of Ba substitution. The Curie temperature and coercive field strength decrease monotonously with the amount of Ba substitution. The mechanical quality factor, Qm, of the thickness-shear vibration mode also decreases. The value of elastic compliance increases with the amount of Ba substitution, but conversely its temperature dependency decreases.

Relationship between poling condition and heat resisting properties in lead zirconate titanate

Poling conditions and heat resisting properties were discussed for lead zirconate titanate (PZT) ceramics. High poling (dc field applied from above Curie temperature to below Curie temperature on specimens) and normal poling (dc field applied from below Curie temperature) were applied as poling methods. As a result, high poling was found to give superior heat resisting properties to normal poling. Moreover, distinct domain structures were observed by microstructural analysis in the high poling sample, and it was found that these domain structures remained stable during heat testing. From these results, it was concluded that high poling resulted in a stable domain structure and consequently brought about superior heat resisting properties.

Effect of Al2O3 Additives in PZT-Pb(Mn1/3Nb2/3)O3 Ceramics

The effect of adding Al2O3 to the PZT-PMN solid solution material for use for ceramic resonator was investigated. It has been found that when the amount of Al2O3 added to PZT-PMN is 0.3　wt% or below, it exists inside the crystal lattice as Al3+ ion and increases the stability of oscillation frequency over application of heat (heat resistance). It has been found that when more than 0.3　wt% of Al2O3 is added, the Al3+ ion that remained undoped will exist at grain boundary as secondary phase, and increase the strength.