Development of Ferrite Materials and Their Applications

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Dr. Takeshi Takei, a professor at Tokyo Institute of Technology, discovered that oxides containing zinc and iron have distinguished magnetic properties, while he carried out the search for ways to raise the yield of zinc in the refining through hydrometallurgy, under the guidance of Prof. Yogoro Kato. This breakthrough led Takei to examine the chemical compositions of a variety of other divalent metal combinations. At the same time, efforts to sinter powder-compacted ferrite under a host of conditions resulted in a magnetic material with superior magnetic permeability and suppression of core-loss, making it suitable for practical high-frequency applications for inductor cores. In 1930 he published scientific paper for Mining Society of Japan, continually gave a presentation at annual meeting of American Electrochemical Society in St. Louis USA. In the same year, a patent application for this material, naming Yogoro Kato and Takeshi Takei as co-inventors, was applied in Japan, and granted in 1932. Following the patent application in 1930, researchers led by Teiichi Yamazaki, who would later become the second president of TDK continued to develop materials with high magnetic permeability and low loss properties by combining divalent metal oxide compounds. In February 1936, Yamazaki developed a ferrite with high magnetic permeability and low-loss properties suitable for practical applications by optimizing the chemical compositions and processing conditions for Cu-Zn ferrite. Tokyo Denki Kagaku Kogyo (now TDK Corporation) was founded in 1935 to commercialize this newly invented ferrite cores as a venture company originated from the university patent of ferrite. TDK started mass production of ferrite cores in 1937. Most of the shipped products were used in the local oscillators, mixers, and intermediate frequency transformers of military radios. These are the world first usage of ferrite to radio communication equipment. Ferrite largely contributed to reduce volume and weight of radio receiver compared with air coil. Until the end of the World War II, TDK was the only company in the world who could supply ferrite cores. TDK shipped a cumulative total of nearly 5 million pieces of ferrite cores by 1945. The electric and electronics industries use ferrites in numerous applications today. Nowadays, numerous numbers of ferrites are used not only for the radio communication equipment, but also for various kinds of devices, such as magnetic core of power converters, noise suppression devices, spintronics devices and medical applications. The development of Ferrite materials and their Applications, 1930–1945, was awarded as an IEEE Milestone on 13th of October 2009, IEEE Milestone in Electrical Engineering and Computing, 2009. Ferrite will be used more for mobile communication tools and automobile applications.