Structural, dielectric, impedance and modulus spectroscopy of Bi_2NdTiVO_9 ferroelectric ceramics

摘要

Detailed studies of electrical and resistive properties of Bi_2NdTiVO_9 (a member of the Aurivillius family), fabricated by a method of standard high-temperature solid-state reaction, are discussed here. The compound crystallizes in the orthorhombic crystal structure. The surface morphology studies show a uniform distribution of grains. The single semicircle of the complex impedance plot and the value of the nonlinear coefficient of the J~E graph suggest that the polarization in the material is due to grain effect only. The semiconducting nature (i.e., negative temperature coefficient of resistance) is observed in the temperature dependence of bulk resistance and J-E characteristics of the sample. The frequency dependence of impedance and electrical modulus of the material shows the existence of non Debye-type of relaxation. The activation energy obtained from the relaxation and conduction processes is found to support the activation of oxygen vacancies in the compound. An analysis of ac conductivity, based on the Jonscher's power law, suggests that the conduction mechanism in the material can be explained using CBH model (i.e., hopping of oxygen ions between vacancies). The nature and existence of electric field dependent polarization (P-E hysteresis loop) at room temperature show that the material has ferroelectric property.