High remnant polarization, high dielectric constant and impedance performance of Nb/In Co-doped Bi0.49La0.01Na0.49Li0.01TiO3-δ ceramics

Abstract

The new ferroelectric oxides, Bi0.49La0.01Na0.49Li0.01Ti0.99(Nb1-xInx)0.01O3-δ (hereafter abbreviated as BLNLTN1-xIx), with x = 0.5–0.65 were fabricated using conventional solid state reaction method. The effects of Niobium (Nb) and Indium (In) as B-site substitutions on phase, microstructure, dielectric, ferroelectric, complex impedance and complex electric modulus properties were systemically analyzed. Hysteresis graphs indicated that BLNLTN0.5I0.5 comparatively have the highest remnant polarization (Pr) of about 49.83 µC/cm2. Moreover, the dielectric studies of BLNLTN0.5I0.5 showed the highest relative dielectric constant (εr) i.e. 4599.3 in comparison to all other compositions. In addition, it also indicated very small loss of <0.045 at 1kHz over a broad range of temperature i.e. room temperature (RT) to 380°C. By comparing BLNLTN0.5I0.5 with BNT, Pr and εr were increased 13.46% and 26.3%, respectively whereas coercive electric field (Ec) and tanδ were decreased 41.06% and 1.96%, respectively. The impedance analysis for BLNLTN0.5I0.5 revealed a gradual decrease in bulk resistance (Rb) with the increase in temperature. Also, it showed negative temperature coefficient of resistance (NTCR) property at 500–800°C and a polydispersive non-debye type relaxation at 800°C. The complex electric modulus analysis proved that effect is mainly due to the bulk grains. Their basic analysis i.e. XRD and SEM studies showed a single phase perovskite structure, spherical grain shape and decreasing average grain size trend with increasing x content. The overall analysis has confirmed the significance of Nb/In co-doping in Bi0.49La0.01Na0.49Li0.01TiO3-δ and showed it as a capable dielectric material for fabricating high-temperature ceramic capacitors.