Yoichiro Masuda

Ferroelectric and antiferroelectric properties of (Na 0.5Bi 0.5)TiO3-SrTiO3 solid solution ceramics

Abstract Phase transitions in the solid solution Sr χ(Na 0.5Bi 0.5)l-χTiO3 have been studied by dielectric, pyroelectric and D-E characteristic measurements. An intermediate antiferroelectric phase has been observed in the composition range of 0 ⩽ χ ⩽ 0.5 of this system. These compositions undergo a ferroelectric-antiferroelectric-paraelectric sequence of transitions at elevated temperatures. The antiferroelectric phase transition temperature and Curie point decrease monotonically with increasing SrTiO3 concentration.

Crystal Growth, Dielectric and Polarization Reversal Properties of Bi4Ti3O12 Single Crystal

A Bi2O3-TiO2 phase diagram was determined using differential thermal analysis (DTA) apparatus. Bi4Ti3O12 (BIT) micalike single crystals grown by a flux method were clear and slightly grayish in color. Ferroelectric and dielectric properties of BIT crystals were observed from measurements of electric displacement vs electric field hysteresis loops and the dielectric constant. Also, the polarization switching characteristics of BIT crystals were investigated. The switching time and switching current density were read from the transient waveforms.

Preparation of Bi4Ti3O12 films on a single‐crystal sapphire substrate with electron cyclotron resonance plasma sputtering

Bi‐Ti‐O oxide thin films were prepared on a sapphire single‐crystal substrate by electron cyclotron resonance (ECR) plasma sputtering. The target used was a sintered Bi4Ti3O12(BIT) and the substrate was controlled in the temperature range 400–640 °C(Tsub). The film sputtered at Tsub=400 °C was a pyrochlore type oxide(Bi2Ti2O7), which changed to a Bi4Ti3O12 oxide in the polycrystalline state at 500 °C and in the single crystalline state at 640 °C. In the film sputtered at 640 °C, the (001) plane of the Bi4Ti3O12 grew parallel to the (1120) and (1102) planes of the sapphire substrate, and the (104) plane of Bi4Ti3O12 grew parallel to the (0001) plane of the sapphire substrate. The deposition rate was about 200 A/min independent of the sputtering conditions.

The Influence of Various Upper Electrodes on Fatigue Properties of Perovskite Pb(Zr,Ti)O3 Thin Films

Ferroelectric thin films of Pb(Zr,Ti)O3 (PZT) were prepared by chemical solution deposition (CSD). The top electrodes of platinum (Pt), SrRuO3 (SRO), and IrO2 thin films are deposited on the PZT thin films by RF magnetron sputtering (RF) and the pulsed laser deposition (PLD) methods, respectively. The polarization fatigue of ferroelectric thin-film capacitors is investigated. As a result, the remanent polarization value of the PZT thin films of SRO/PZT/PT/Pt/TiOx/SiO2/Si and IrO2/PZT/PT/Pt/TiOx/SiO2/Si remains more than 1011 switching cycles at constant value and the value of the PZT thin films of Pt/PZT/PT/Pt/TiOx/SiO2/Si decreases to approximately 50% of its initial value at 108 cycles. It is confirmed that polarization fatigue is improved using SRO and IrO2 thin-film electrodes as top electrodes.

Influence of crystal phases on electro-optic properties of epitaxially grown lanthanum-modified lead zirconate titanate films

We describe here how we have improved the crystal qualities and controlled the crystal phase of the lanthanum-modified lead zirconate titanate (PLZT) film without changing the composition ratio using an oxygen-pressure crystallization process. A PLZT film deposited on a SrTiO3 substrate with the largest electro-optic (EO) coefficient of 498 pm/V has been achieved by controlling the crystal phase of the film. Additionally, a fatigue-free lead zirconate titanate (PZT) capacitor with platinum electrodes has been realized by reducing the oxygen vacancies in the films.

A Double-Layer Electrically Controlled Birefringence Liquid-Crystal Display with a Wide-Viewing-Angle Cone

An electrically controlled birefringence (ECB) LCD (liquid crystal display) has the problem of narrow viewing angle. To solve this problem, a double-layer ECB (D-ECB) LCD with a wide-viewing-angle cone under the application of voltage is proposed. In this device, each layer compensates for the variation of retardation as a function of viewing angle. This double-layer optical compensation method can be applied not only to a birefringence mode but also to an absorption mode, i.e. guest-host mode.<<ETX>>

Investigation into Electrical Conduction Mechanisms of Pb(Zr,Ti)O3 Thin-Film Capacitors with Pt, IrO2 and SrRuO3 Top Electrodes

The conduction mechanisms of Pb(Zr,Ti)O3 (PZT) thin-film capacitors with Pt bottom electrodes and Pt, IrO2 and SrRuO3 (SRO) top electrodes were investigated. In the case of SRO top electrode prepared by pulsed laser deposition, the Schottky barrier was not formed at the interface due to the interdiffusion and the space-charge-limited current with a trap energy of 2.1 eV was dominant. On the other hand, for the Pt and IrO2 top electrodes prepared by sputtering, the capacitors showed the Schottky emission current at low electric field and the Fowler-Nordheim current at a high electric field. The Schottky barrier heights for Pt/PZT and IrO2/PZT interfaces were estimated to be 0.93 and 0.67 eV, respectively. An ultra thin alteration layer between the Pt top electrodes and PZT films seems to degrade the barrier height of the Pt/PZT interface. Furthermore, the Pt/PZT/Pt capacitor showed negative resistance at room temperature. We concluded that the potential well formed near the top interface by band bending is the origin of this negative resistance.

Variation of Dielectric Constant Affected by Domain Structure and Electric-Field-Induced Strain in Ferroelectric Ceramics

The dc electric bias and frequency dependence of the dielectric constants for lead zirconate titanate (PZT) ceramics with ferroelectric phase were measured at room temperature for several frequencies from 1 kHz to 1 MHz. The variation of dielectric constants versus biasing field and frequency was explained by introducing 180° and 90° domains. The actual strain measurement of ceramics was performed by a potentiometer. Assuming that the strain was caused by piezostriction and electrostriction, the piezostriction and electrostriction coefficients were determined by the least squares method, and the spontaneous strain induced by an internal electric field was discussed.

Preparation of Ba2NaNb5O15 film by RF magnetron sputtering method

A film with tungsten-bronze structure was formed on a Pt/Al 2 O 3 substrate by a RF magnetron sputtering method. The deposition ratio of the films (Ba:Na:Nb) depended on the sputtering gas pressure. When the deposition rates were 10 nm/min at 10 -1 Pa and 5 nm/min at 8 Pa, the dielectric constant and the dielectric loss factor were 141 and 0.02 at room temperature, respectively, and the remanent polarization P r and the coercive field E c were 32 μC/cm 2 and 576 V/mm, respectively

Preparation and Dielectric and Electrooptic Properties of Bi4Ti3O12 Films by Electron Cyclotron Resonance Plasma Sputtering Deposition

Polycrystalline and epitaxlal films of a layer-structured ferroelectric Bi4Ti3O12 in perovskite phases have been deposited on sapphire substrates by ECR plasma sputtering using a sintering ceramic target. The substrate temperature higher than 550°C is necessary to grow Bi4Ti3O12 films in the perovskite phase without post-thermal annealing. Bi4Ti3O12 films were epitaxially grown on C, A and R surfaces of a sapphire single crystal. Refractive indices of Bi4Ti3O12 films were determined from measurements of the Brewster angle, and the dielectric constant was measured at 1 kHz using an ADEX-221A LCR meter.