Identification of the electromechanical material properties of a multilayer ceramic capacitor

A multilayer ceramic capacitor (MLCC) vibrates when an electrical signal containing an alternating current (AC) component is applied to it. The piezoelectric and electrostrictive coefficients of the dielectric layer are needed to analyze such vibrations because both affect the vibration. Also, they must be determined for various direct current (DC) biases because an MLCC is operated with various electrical signals and the coefficients vary as the DC bias changes. We determined the coefficients by measuring the vibration of an MLCC under a range of DC biases. When a single-frequency AC voltage is applied to an MLCC, it vibrates with both fundamental and second-harmonic frequencies because of piezoelectricity and electrostriction. These frequencies were measured and separated into their piezoelectric and electrostrictive components to derive the piezoelectric and electrostrictive coefficients. Because of the difficulty of calculating the coefficients, a finite element (FE) method was adopted in consideration of the complicated structure of the MLCC. The derived piezoelectric coefficients were cross-checked and verified by impact testing. The electrostrictive vibration component was greater than the piezoelectric one except when the applied DC electric field was near zero. This showed that both piezoelectricity and electrostriction must be considered in vibrational analyses of MLCCs.