History

The piezoelectric effect was discovered by Jacques and Pierre Curie in 1880. The initial observation was the development of charge on a crystal proportional to an applied mechanical stress. Soon thereafter the converse effect, the geometrical strain of a crystal proportional to an applied voltage has also been shown.
 
The potential commercial use of piezoelectric materials as transducers was recognized as early as 1917, when the first underwater ultrasonic submarine detector was proposed. Although many potential applications have been identified, phonograph pickup installations based on single crystal Rochelle salt were the major applications in the era form 1935 to about 1950.
 
During World War II several consecutive discoveries lead to a new wave of developments and eventually applications. The first findings of unusual piezoelectric properties in refractory oxides (more specifically barium-oxide, titanium-oxide compositions) were made in 1941, which was an important step as most commercially available piezoelectric elements today are still oxide based. The next key step was to understand the mechanisms of piezoelectricity in these materials. Several publications around 1945 reported unusual dielectric properties in Barium-Titanate and tried to explain the physical principle on a molecular level. One of the most significant discoveries was the poling process in polycrystalline piezoelectric materials in 1946. Until then the piezoelectric effect was only observed on single crystal materials, which are generally more expensive to manufacture and limited in size.
 
Having the option to use more easily accessible polycrystalline materials fuelled many of the applications which were realized in the post World War II era. An advancement of great practical importance was the discovery of very strong and stable piezoelectric effects in lead zirconate solid solutions by B. Jaffe and co-workers in 1954. This has initiated exciting developments and led to an enormous field of applications based on piezoelectric materials.