New Era In Devices

UNTIL now the piezomagnetic transducer has offered a much higher efficiency than the piezoelectric in most applications.

So, 65 years ago, started a story in Electronics Weekly’s edition if October 19 1960

The story continues:


The recent announcement by Bell Telephone Laboratories of materials with up to four times as great an activity as quartz may well mean a much greater use of niezo. electricity in the future.


Two basically common materials. zinc oxide and cadmium sulphide. have been revealed as possessing marked piezoelectric properties Dr. A R. Hutson, of Bell Tele-phones, decided to investigate the situation while studying some of their unusual conductivity properties.

A large piezoelectric constant seemed to explain certain anomalies theoretically, but had never been observed experimentally.

The main trouble was the low resistivity of the material. In the case of zine oxide this was “quenched” by diffusing lithium atoms into the material, to act as acceptors for the excess electrons which were contributing to the conductivity. When this was done the resistivity was raised from 103 to 1012 ohm/cm at room temperature..

Resonance / anti-resonance measurements and direct squeeze measurements were made on specimens.

Dielectric constants of 8.2 and 9 for zinc oxide and cadmium sulphide respectively were measured; electromechanical coupling coefficients were calculated to be approximately 0.4 for zine oxide and 0.2 for cadmium sulphide, compared to 0.095 for quartz.

These coupling coefficients appear to be as high, or higher than those obtained with piezo-magnetic transducers, and may offer other advantages also.

It  would thus appear that considerable use could be made of them in electromechanical transducers of high efliciency.

 

David Manners

David Manners

David Manners has more than forty-years experience writing about the electronics industry, its major trends and leading players. As well as writing business, components and research news, he is the author of the site's most popular blog, Mannerisms. This features series of posts such as Fables, Markets, Shenanigans, and Memory Lanes, across a wide range of topics.

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