Uniaxial Stress Dependence of the Static Dielectric Constant of Some Alkali Halides

A sensitive method to measure the strain derivatives of the static dielectric constant of uniaxially stressed crystals is described. With stress modulation and phase‐sensitive detection, changes as small as 5 × 10 −7 of the sample's capacitance can be detected. The piezodielectric and electrostrictive tensor components of LiF, NaCl, and KCl are given. The experimental results are compared with theoretical estimates of these coefficients based on lattice dynamical models.