Papers by Author: Takashi Iijima

Abstract: Pr-substituted Bi4Ti3O12 (BPT, Bi4-xPrxTi3O12, x=0.1-0.4) polycrystalline thick films with a-/b-axes orientations and thickness of 2-3 μm were grown on sputter-grown IrO2 layers by chemical solution deposition method for developing lead-free piezoelectric film microdevices. Electric-field-induced strains measurements were performed by double-beam laser displacement meter and longitudinal strain of e=0.25 % under 400 kV/cm and piezoelectric coefficient d33=63 pm/V at 10 Hz were observed in BPT thick film of x=0.1 with a-/b-axes mixed orientations. The value of strain closely related to spontaneous polarization and monotonously decreased with increasing x. Microstructures of 3 μm-thick BPT films were fabricated by photolithography and dry etching processes with several tens micrometers in size.

Abstract: Nd-substituted Bi4Ti3O12 (BNT) polycrystalline thin films with preferred a-/b-axes orientations were grown on sputter-grown IrO2(101) layers by chemical solution deposition method. After optimizing the heat treatment conditions, insulating characters and ferroelectric properties in 250-nm-thick BNT thin films with a-/b-axes orientations were investigated at room temperature. Low leakage current density of J=10-7~10-8 A/cm2 at 100 kV/cm and fair value of remnant polarization (2Pr=31 μC/cm2 at 400 kV/cm) were measured even though the Bi2O2 blocking layer aligned parallel to the film normal.

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.

Abstract: A series of Pb(Ti1-xAlx)O3, Pb(Ti1-xNbx)O3 and Pb(Ti1-xAlx/2Nbx/2)O3 thin films were fabricated onto Pt/Ti/SiO2/Si(100) substrates using a chemical solution deposition process. The dielectric constant of the Pb(Ti1-xAlx)O3 thin films increased with increase of aluminum content, while a maximum dielectric constant value was observed for the Pb(Ti1-xNbx)O3 and Pb(Ti1 xAlx/2Nbx/2)O3 thin films when the doping contents were 10 and 20 mol%, respectively. The dielectric constant of the Pb(Ti0.8Al0.1Nb0.1)O3 thin film is about 600, being two times higher than those of Pb(Ti0.9Al0.1)O3 and Pb(Ti0.9Nb0.1)O3 thin films. The Pb(Ti0.8Al0.1Nb0.1)O3 thin film showed less than 10-7 A/cm2 current density at ±150 kV/cm, being superior to the leakage property of the PbTiO3, Pb(Ti0.9Al0.1)O3 and Pb(Ti0.9Nb0.1)O3 thin films. The co-doping of aluminum and niobium is more effective to increase the dielectric and ferroelectric properties as compared with the individual aluminum or niobium doping.