1. Definitions of piezoelectricity

1.1 Piezoelectricity

The appearance of electrical charges when mechanical stress is applied to a natural crystal was first observed by a French mineralogist, Abbé R. Haüy, in 1817. It was later, in 1880, that Pierre and Jacques Curie, working on the relationship between crystal structure and the physical properties of crystals, experimentally discovered the direct effect of piezoelectricity. They observed this electro-mechanical coupling effect in a large number of crystals such as quartz, tourmaline (a group of minerals in the silicate family, crystallizing in the trigonal crystal system, space group R3m) and Rochelle salt (the common name for sodium-potassium double tartrate), and based on the study of their symmetry properties, they proposed the first laws describing direct piezoelectricity...