Mechanism analyses of differential and static dielectric constants in ferroelectrics

Abstract

Abstract The dielectric constant measured by the LCR-meter is a differential-type, and is not equivalent to capacitivity. Capacitivity of ferroelectrics is the dielectric constant corresponding to electric hysteresis loop. Two kinds of dielectric constants are investigated based on the P-E loop mechanisms: turning effect of dipoles toward electric field direction, electric field-induced polarization effect, and dipole coupling effect. Numerical simulation of the theoretic equations exhibit adouble-peak of the differential dielectric constant, in which the distance between the two peaks depends on the temperature and the electric field. A much narrow static dielectric constant peak and negative peak appear corresponding to the loop. Mechanisms are analyzed schematically in detail. HIGHLIGHTS Definitions of differential- and static-dielectric constant are introduced and compared. Theoretic equations for the two dielectric constants are derived from the three effects. Variations of the two dielectric constants with E and T are demonstrated schematically. Mechanisms of the variations are explained in detail.