Dielectric characteristic of fatigued Bi4-xLaxTi3O12 ferroelectric films

Dielectric measurement was carried out on fatigued Bi_4-xLa_xTi₃O₁₂ ferroelectric films. It is found that the dielectric permittivity varies with switching cycles. With the increase of the switching cycles, the dielectric permittivity exhibits a continuous decrease. This decrease is pronounced for BiT films with low concentration of La, while it is slight for Bi_4-xLa_xTi₃O₁₂ films with high concentration of La. Dielectric permittivity was also measured on Bi_4-xLa_xTi₃O₁₂ ferroelectric films fatigue at different frequencies 50 kHz and 20 kHz. It exhibits that the decrease of dielectric permittivity is pronounced if the films were fatigued at low frequency, while this decrease is slight if the films were fatigue at high frequency. It is proposed that a growing of an interface layer appears during the fatigue process.