Hidetoshi Tsuchiya

Dependence of Resistivity on Donor Dopant Content in Barium Titanate Ceramics

Barium titanate ceramics doped with yttrium as well as silica and alumina have been studied with special reference to the effects of the yttrium content. An yttrium content at which the ceramics showed a minimum resistivity increased with the increase of the sintering temperature and the added amounts of SiO2Al2O3. The microstructural studies with the electron probe X-ray microanalyzer revealed that these results should be explained in terms of the grain growth inhibitor effects of yttrium and the segregation of it to grain boundaries.

Memory modes of ferroelectric field effect transistors

Abstract Effects of traps on the memory characteristics of ferroelectric field effect transistors with the metat-ferroelectric-insulator-semiconductor structure were theoretically analyzed. Various modes of operation, i.e. the polarization-limited mode, trap-limited mode, critical field-limited mode, MNOS mode and probability-limited mode, were derived depending on the device parameters. Experimental devices with gate insulator BaTiO3 or PLZT were fabricated by using thin film SnO2 and thin film Te. The memory characteristics of these devices were interpreted in terms of the trap-limited mode and MNOS mode, respectively.

Ferroelectric Films Deposited by Reactive Sputtering and Their Properties

Thin films of ferroelectric materials (PZT and PLZT) have been deposited by dc reactive co-sputtering from composite metal target. Although the structure of the resulting films without substrate heating was proved as amorphous through X-ray diffraction, it can be changed to provide a desired perovskite structure by subsequent heat-treatment in a lead-compensated atomosphere. Some of the films, after poling in the planar direction, showed an obvious piezoelectric activity.

Design principles for multilayer piezoelectric transformers

Abstract Multilayer piezoelectric transformers with various internal electrode patterns have been studied in this paper. Dependence of the electrical properties of transformers on the number of layers was examined and then design principles are indicated about it. The multilayer piezoelectric transformer is superior to the conventional one in view of large output current.

Multilayered piezoelectric transformer

Abstract Since a green sheet of PZT ceramics is nowdays tapecast on a polymer film with comparative facility by using the so-called doctor-blade method, a capacitor and an actuator are produced for trial, having appropriate internal electrodes within, and their beneficial effects are stated with great emphasis. The effects of internal electrodes should be ascertained, as a rule, first, by investigating the functional characters of the device and, then, by analysing the computer simulation. Each sheet of a multilayer piezoelectric transformer fabricated as the subject of this paper has patterns of internal electrodes contrived in order to avoid delamination, and, in addition, the functional characters due to internal electrodes are made clear in this paper. From a practical standpoint, output voltage and current are, especially, expected and examined.

Poling Treatment of Sputter-Deposited PZT Films

Ferroelectric PZT films were successfully fabricated by reactive magnetron sputtering using a composit metal target. The films often showed asymmetric hysteresis loops which were brought about by a spontaneous internal biasing field. The field also affected stability of the poled film during application of a high ac voltage. In some cases, films without poling treatment showed evident pyroelectric response.

Loop tracer with waveform storage for ferroelectric hysteresis observation

The present paper describes a loop tracer devised for ferroelectrics that can record hysteresis phenomena instantaneously. Digital technology has been applied to the conventional Sawyer–Tower circuit to provide a new system. Owing to its fast operation, it is easy to observe the loop of aged specimens without changing their electrical state, as well as to follow the depolarizing process dynamically when an ac voltage is applied.

Piezoelectric inverter using thin plate transformer

Abstract In order to apply a piezoelectric transformer to back lighting fluorescence lamp in a liquid crystal display, asymmetric extension vibration mode of a piezoelectric rectangular plate has been investigated with special reference to the power transfer efficiency upon electrically loaded by the fluorescence lamp. In spite of a simple and thin monolithic structure, the optimum transformer, 21.3 × 11 × 0.5 mm in size, indicated 96% power efficiency as well as up to 30 step-up ratio which corresponds to more than 4 times that of the conventional Rosen-type transformer. The transformer has been successfully incorporated into a small size inverter unit together with a newly developed IC element for controlling frequency to the resonance, with less than 2.2 mm total thickness.

A Loop Tracer for Instantaneous Measurement of Ferroelectric Hysteresis Phenomena

The paper describes a loop tracer for observing hysteresis phenomena in ferroelectrics; the tracer utilizes recent digital technology and can record the hysteresis phenomena instantaneously. As the operation speed is very fast, it is easy to observe the loop of aged specimens without changing their electrical state, as well as to trace the depolarizing process dynamically when an ac voltage is applied. From the data obtained a new representation for ferroelectric hysteresis curve has been proposed and discussed with special reference to determination of an internal bias field in the materials.