Papers by Author: Masahiko Kimura

Abstract: Barium titanate (BaTiO₃, BT) grain-oriented ceramics were prepared by electrophoresis deposition (EPD) method under high magnetic field (HM-EPD) of 12 T. For this objective, the BT single-domain nanoparticles with high c/a ratio of 1.008 and size of 103 nm were prepared by two-step thermal decomposition method. Using the BT nanoparticle slurry, BT nanoparticle accumulations were prepared by EPD or slipcasting (SC) methods with/without high magnetic field. After binder burnout, these accumulations were sintered at 1350 °C and it was revealed that only the BT ceramics prepared by the HM-EPD method was assigned to grain-oriented ceramics with weak preferential crystallographic orientation along [11 direction.

Abstract: Fatigue tests on lead zirconate titanate (PZT) were performed by using single-edge-V-notched specimens under cyclic mechanical loading with or without superposition of a DC electric field. Fatigue life was prolonged by applying a DC electric field to the PZT ceramics. To estimate the domain contribution, fatigue tests on barium strontium titanate (BST) ceramics in both ferroelectric and paraelectric phase were carried out. The fatigue life of the ferroelectric phase was much shorter than that of the paraelectric phase. Comparing the fatigue lives of two PZT ceramics with different values of coercive electric field (E_c) revealed that the fatigue life of the PZT with higher E_c is about one order of magnitude longer than that with lower E_c when the stress-intensity factor of fatigue test is low. It is therefore concluded that non-180°domain switching probably deteriorates the fatigue life of ferroelectric ceramics.

Abstract: Grain-oriented Barium titanate (BaTiO₃) ceramics were prepared using an electrophoresis deposition (EPD) method under high magnetic field of 12 T and sintering at 1350 °C. It was found that BT03 and BTKK nanoparticles were necessary to synthesize the grain-oriented BT ceramics. The grain orientation was correlated with particles size and c/a ratio of lattice constants. The reason why the grain-oriented BT ceramics using the BT03 and BTKK were prepared was having the large values of the particles size and the c/a ration of lattice constants.

Abstract: The structural, and dielectric and piezoelectric properties of (1-x)BaTiO3 – x Bi_1/2K_1/2(X_1/3Nb_2/3)O₃ (X=Cu, X=Mg or X=Zn) ceramic were studied. The single perovskite phase was observed when x≤0.5 for X=Cu and Mg and x≤0.2 for X=Zn. As x increased, the dielectric constant peak temperature and piezoelectric properties continuously decreased for X=Mg and Zn. On the other hand, those of X=Cu possessed a local maxima at x=0.7 and the peak temperature was 200°C and the large field piezoelectric constant, d₃₃*, was 94 pC/N.

Abstract: Textured PbTiO3 (PT) ceramics were fabricated by slip casting in a high magnetic field of 12 T. The sample obtained from the powder calcined at 1100 °C was (100), (010), and (001)-oriented, and the orientation factor was 90 %. On the other hand, the sample obtained from the powder calcined at 900 °C was not oriented. Aggregability and crystallinity of powder are an important factor when textured ceramics are fabricated by slip casting in a high magnetic field.

Abstract: Ceramic materials based on lead titanate, lead niobate and bismuth layer-structured ferroelectrics (BLSF) were studied to develop piezoelectric ceramics for high temperature sensor applications. Compositional modification enabled lead titanate and lead niobate type ceramics to exhibit good piezoelectric properties at 500°C . The Curie temperature for one BLSF, CaBi4Ti4O15 was close to 800°C, though the piezoelectric constant was smaller than those of lead titanate and lead niobate ceramics. These ceramics seem to be good candidates for use as high temperature sensor materials. In addition, textured SrBi2Nb2O9 (SBN), another BLSF, ceramics with various orientation factors were fabricated through the templated grain growth (TGG) method. The resonant frequency of 76% textured SBN varied linearly with temperature and exhibited stable temperature characteristics. The temperature coefficient of the resonant frequency was –0.85 ppm/°C from –50 to 250°C, and was smaller than that of a quartz oscillator. Therefore, textured SBN ceramics are suitable for use as a resonator material when stable resonant frequency is needed in a high temperature range.

Abstract: A study has been done for the piezoelectric properties in texured ceramics of SrBi2Nb2O9 (SBN) fabricated by the templated grain growth (TGG) method. Remanent polarization along to the stacking direction increased with the orientation degrees. That corresponds to the increases in electro-mechanical coupling coefficient with orientation degree. The temperature coefficient of the resonant frequency (TCF) in thickness sheer vibration mode changed from negative to positive with increasing orientation degrees, and an excellent TCF of -0.4 ppm/°C was obtained for the specimen with an orientation degree of 76%.