Fundamentals of Piezoelectrics

Certain materials produce electric charges on their surfaces as a consequence of applying mechanical stress. The induced charges are proportional to the mechanical stress. This is called the direct piezoelectric effect and was discovered in quartz by Pierre and Jacques Curie in 1880. Materials showing this phenomenon also conversely exhibit a geometric strain proportional to an applied electric field. This is the converse piezoelectric effect, discovered by Gabriel Lippmann in 1881. This article reviews the fundamentals of piezoelectrics; (1) microscopic origins of the electric-field induced strain, (2) piezoelectric constitutive equations, (3) figures of merit in piezoelectrics, (4) resonance and antiresonance, and (5) piezoelectric materials, and finally brief introduction of (6) applications of piezoelectrics for sensors, actuators, transducers etc.