piezoelectricity: a standalone construct

Jacques Curie and Pierre Curie first reported piezoelectricity in 1880, showing that certain crystals such as quartz, tourmaline, and Rochelle salt develop measurable surface electric charge when they are squeezed or stretched, with the charge reversing sign when compression becomes tension. The following year Gabriel Lippmann predicted, and the Curies confirmed, the converse effect, in which the same crystals change shape when a voltage is applied across them, so the coupling runs both ways between mechanical strain (deformation) and electric polarization (a separation of positive and negative charge). Walter Cady's 1946 treatise Piezoelectricity systematized the theory and its engineering uses, and later work such as Dragan Damjanovic's 1998 review extended it to the ceramics and thin films used today. The effect arises only in crystals that lack a center of symmetry: of the 32 crystal classes, 20 permit piezoelectricity, so the property is fixed by a material's internal symmetry rather than by its chemistry alone. This structural requirement, together with the two-way conversion between force and voltage, is what makes piezoelectricity the physical basis for quartz clock oscillators, ultrasound and sonar transducers, and many pressure, vibration, and acceleration sensors.[1][2][3]

Unit

A material property of certain crystals: the linear coupling between mechanical stress and electric charge, reported as piezoelectric coefficients (the d coefficient, in picocoulombs of charge per newton of force)

Recovery means

Not applicable

Measured by

Measured by applying a known force to a crystal and recording the charge or voltage produced, or through the converse effect as strain per unit applied field, yielding the piezoelectric coefficient tensor