Papers by Author: Jun Akedo

Abstract: (Bi_0.5Na_0.5)TiO₃ (BNT) single crystals were grown by flux method at a high oxygen pressure (Po₂) of 1 MPa, and their polarization properties were investigated. BNT single crystals exhibited a saturated polarization hysteresis with a remanent polarizations (P_r) of 31 μC/cm² along [100]_c, 44 μC/cm² along [110]_c and 54 μC/cm² along [111]_c. These results show that spontaneous polarization of BNT is approximately 55 mC/cm² or larger.

Abstract: To retain the driving properties of metal-based micro optical scanner derived by aerosol deposition (AD) technique, CO2 laser irradiation was used to anneal the PZT films deposited onto the stainless-steel substrate. Stainless-steel mirror and frame of the scanner with the film annealed by laser irradiation maintained their metallic luster. The scanner with the film annealed by laser irradiation at 600 °C for 1 min has a scanning angle over 30 degree that is comparable with the scanning angle of a similar scanner annealed by electric furnace at 600 °C for 10 min.

Abstract: (Ba0.6,Sr0.4)TiO3 thick films have been fabricated on various substrates and their physical and electrical properties were analyzed. The effect of primary powder condition on the quality of the BST fabricated films using aerosol deposition technique has been investigated keeping in mind results shown in the literature for BST films fabricated with classical deposition techniques. Presence of carbonates and TiO2 has been demonstrated by XPS analysis and the leakage current behavior has linked to the presence of TiO2 at the grain boundaries. The films showed good insulating properties, with small leakage densities being on the order of 10-6 A/cm2 for an applied electric field of 150 kV/cm.

Abstract: The ultrasound probes utilized in this study were fabricated using lead zirconium titanate (PZT), which was deposited using two different methods—the aerosol deposition (AD) method and the hydrothermal method. The fabricated ultrasound probes had the same structure wherein an electrode and an acoustic backing block were attached to each transducer. In this study, we have compared the acoustic characteristics of a high-frequency ultrasound probe fabricated by the AD method with those of a probe fabricated using the hydrothermal method; further, we have studied and hence determined the optimal process that can be used in the fabrication of high-frequency ultrasound probes with a resonance frequency of 40 MHz. As a result, when the pickup voltage was compared, the ultrasound probes fabricated by the AD method exhibited a value 9.5 times higher than that of the probes fabricated by the hydrothermal method. Moreover, the ultrasound probes fabricated by the AD method were found to transmit pulses at resonance frequencies of 28 MHz, 45–50 MHz, and 82–88 MHz.

Abstract: Characteristics of heating processing based on millimeter-wave or pulsed high current are discussed from the standpoint of the interaction between electromagnetic energy and solid materials. Capabilities of the electromagnetic processing are indicated by exemplifying several successful results such as millimeter-wave sintering of AlN, millimeter-wave post-annealing of aerosol-deposited PZT films and synthesis of single-phase nano-structured anatase by SPS (or pulsed high current heating). It is shown in these examples that well-characterized properties such as high thermal conductivity and preferential orientation are created by the inherent effect due to the electromagnetic field, which is called microwave or SPS effect in millimeter-wave or SPS processing.

Abstract: In order to fabricate a microstrip band pass filter in GHz region as a passive component of RF modules, Al2O3 thick films were prepared on Cu metal substrates by AD (Aerosol Deposition) process. The dimensions of the filters were determined by the high frequency electromagnetic analysis. The filters were successfully fabricated on AD-derived Al2O3 thick films by employing sputtering, photolithography, electroplating and chemical etching processes. Their filtering characteristics were examined by a Network Analyzer. Through this work, we suggest that the AD process will be important the fabrication technology for integrated RF modules.

Abstract: Aerosol deposition method (ADM) for shock-consolidation of fine ceramics powder to form dense and hard layers is reported. Submicron ceramic particles were accelerated by gas flow in the nozzle up to velocity of several hundred m/s. During interaction with substrate, these particles formed thick (10 ~ 100 µm), dense, uniform and hard ceramics layers. Depositions were fulfilled at room temperature. Every layer has polycrystalline structure with nano-meter order scale.􀀂 The results of fabrications, microstructure, mechanical and electrical properties of oxides (α-Al₂O₃; Pb(Zr_0.52,Ti_0.48)O₃ etc.) and non-oxides materials are presented.