Papers by Author: Yuichi Sakai

Abstract: 0.67BiFeO₃-0.33BaTiO₃ thick films were prepared by screen printing pastes prepared by kneading the 0.67BiFeO₃-0.33BaTiO₃ powder in a three-roll mill with an organic vehicle. The thick films were fired with Pt bottom electrodes and ZrO₂ substrates to investigate the influence of firing temperature. The microstructures and ferroelectric properties of the thick films were examined and compared with the bulk ceramics. A remanent polarization of 32.0 μC/cm² and coercive field of 28 kV/cm were obtained for a thick film with the addition of 0.5 wt% MnO that was fired at 1050 °C.

Abstract: CaBi4Ti4O15 based thick films were prepared by screen-printing method on Si substrates. Screen-printable pastes were prepared by kneading the CaBi4Ti4O15 powder in a three-roll mill with an organic vehicle. The remanent polarization of 6.3 C/cm2 and coercive field of 130kV/cm were obtained for the CaBi4Ti4O15 with Nb2O5 1wt% thick film fired at 1130°C. The cavity structure was prepared by etching of Si substrate. The displacement-electric field butterfly curves were obtained.

Abstract: In order to prepare lead free multi-layer ceramic (MLC) actuators with Ni inner electrodes, inkjet ink containing NiO was prepared and its rheological properties were examined. The viscosity of the ink followed the Andrade's equation. By using this ink, Ba(Ti,Zr)O3 based MLCs were prepared. The printed NiO layers were reduced to metal Ni and they functioned as the inner electrodes. The remanent polarization of the MLCs increased with the grain growth caused by the increase of firing temperature. The remanent polarization Pr and coercive field Ec of the MLCs fired at 1400°C were 6.4 μC/cm2 and 3.5 kV/cm, respectively. The displacement of the MLCs with 7 active layers was approximately 320nm at 30 kV/cm. The effective d33 shows approximately 160 pm/V when the electric field was 10 kV/cm.

Abstract: MBi4Ti4O15 (M=Ba,Ca) thick films were prepared by screen printing and firing using Pt bottom electrodes and ZrO2 substrates. Screen-printable pastes were prepared by kneading the MBi4Ti4O15 powder in a three-roll mill with an organic vehicle. The microstructures and electric properties of the thick films were examined in comparison with bulk ceramics. The remanent polarization of 6.2 9C/cm2 and coercive field of 130kV/cm were obtained for the CaBi4Ti4O15 thick film fired at 1130OC. The Curie points of MBi4Ti4O15 (M=Ba,Ca) thick films from dielectric peaks were 450OC and 790 OC for M=Ba and M= Ca.

Abstract: Bi4Ti3O12 based thick films were prepared by screen printing and firing using Pt bottom electrodes and ZrO2 substrates. The influence of excess Bi2O3 as sintering aid was investigated. Furthermore, substitution of Ti-site and Bi-site for V5+ and Nd3+ was performed. Screen-printable pastes were prepared by kneading the Bi4Ti3O12 based powder and Bi2O3 powder in a three-roll mill with an organic vehicle. The microstructures and ferroelectric properties of the thick films were examined in comparison with bulk ceramics. The remanent polarization of 9.6 μC/cm2 and coercive field of 64 kV/cm were obtained for the Bi3.0Nd1.0Ti2.99V0.01O12 thick film with 10 wt% of excess Bi2O3 fired at 1200OC.

Abstract: [BaO]m(Ti0.975Zr0.025)O2 ceramics with Ni electrodes were prepared by a firing in N2 atmosphere. The dielectric, ferroelectric and piezoelectric properties were examined in terms of the composition. The remanent polarization of 9.5μC/cm2 was obtained for m=1.01 by the addition of 0.5wt% SiO2. The longitudinal piezoelectric constant d33 calculated from a unipolar signal (8kV/cm,10Hz) was 430pC/N. Lead-free multi-layered piezoelectric actuators were fabricated using this material by the tape casting, screen-printing of Ni electrodes, laminating under heat and pressure, and firing in N2 atmosphere. The displacement of the actuator with 75μm x 9 active piezoelectric layers was 0.17μm at an applied voltage of 75V and a frequency of 10Hz.

Abstract: Piezoelectric actuators were prepared by the screen printing of piezoelectric thick films and the wet etching of Si substrates for the application of ink jet printer heads. The Pt bottom electrode was used as the vibration plate to obtain a large displacement. The layer structure and integration processes of the Pt bottom electrodes were investigated to be suited to the whole preparation process of the piezoelectric actuator. The displacement of the center of the actuator with 100 μｍ x mm was 0.03 μm at the applied voltage of 30 V and frequency of 4 kHz.