= Piezoelectricity
{wiki}
Piezoelectricity is linear coupling between mechanical deformation and electrical response in suitable materials. The <direct piezoelectric effect> produces electrical <polarization> under applied <stress>; the <converse piezoelectric effect> produces <strain> under an applied <electric field>. The two responses are linked by the same electromechanical coupling coefficients when conventions and mechanical constraints are specified consistently.
A <piezoelectric stress sensor> uses the direct response to turn force or vibration into an electrical signal. A scanning probe uses the converse response to move a tip by very small distances, controlling a <tunnel junction>'s separation. The resulting displacement can depend on drive history through <piezoelectric hysteresis> and can continue changing after a voltage step through <piezoelectric scanner creep>. These effects motivate calibration and <closed-loop control>.
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