Before WWI, piezoelectricity had not been used outside the laboratory, and had been studied by only few physicists. The war changed that with Paul Langevin’s invention of piezoelectric ultrasonic detection technology, later known as sonar (which would form the core of medical ultrasonic scanning methods). In the war’s aftermath, another physicist, Walter Cady, discovered the sharp and steady electric resonance of piezoelectric crystals, and consequently invented the method of crystal frequency control. Already in the early 1920s, engineers and physicists have realised the importance of this method for radio, telephony and other application of electronics, leading to the invention of the quartz clock in 1927.
This talk will discuss the transformation of the scientific research of the phenomenon following its application, in both content and volume of research. Piezoelectricity attracted unprecedented attention from scientists in universities, and national and industrial research laboratories, becoming an independent sub-specialty in the interbellum. The vast majority of its researchers, like Cady, or the known theoretician Max von Laue, had not studied the field before the war. Most of the research was related to and stimulated by practical devices. In particular, the essential technological role of piezoelectric vibrations moved this hitherto unexamined oscillating crystals to the centre of research on the phenomena. Yet scientists often sought a deeper and more extended knowledge about this and other phenomena, beyond the needs of technology. Technological aims, thus, shaped the research in the filed but did not limit it to questions of expected applicability. Still it seems that the technological application of piezoelectricity had a stronger influence on its knowledge and even on its understanding than developments in the general theories of physics such as the advent of quantum mechanics.