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A new type of ferroelectric which exhibits a threshold switching field and a number of highly useful technical properties is simply distinguished from ordinary ferroelectrics as ferrielectrics. These new materials have been described in detail in various publications. The good industrial properties of the mixed bismuth oxide (MBO) ferrielectrics permitted the extension of work on fundamental research into applied research. The objective of this work was to demonstrate that capacitor elements comprised of MBO-type ferrielectrics exhibiting a threshold field as a dielectric represent an important improvement as compared to ordinary ferroelectric capacitors, and they can be utilized as logic and memory devices. Work was essentially devoted to the following application areas. 1) Improved field controlled polarization transfer devices (Transpolarizers ®) were developed. These transpolarizers utilize internally biased MBO-type ferrielectrics which made it possible to block and unblock the transpolarizer with opposite polarity pulses. Furthermore two-section transpolarizers requiring only ten volts for switching have been fabricated. Due to the improved switching features and low switching levels attained, these transpolarizers are compatible with transistor technology. 2) An exploratory content addressable memory system using these improved transpolarizers was developed and constructed, and its operating features are described.
Date of Publication: Jun 1969