Influence of vanadium substitution on dielectric and electrical characteristics of NaNbO3 ceramics in polymorphic R and S phase

Abstract

The lead-free polycrystalline NaNb1−xVxO3 (NV: 0.00 ≤ x ≤ 0.06) samples are prepared by standard solid-state reaction technique. Room temperature X-ray diffraction (XRD) analysis suggests an orthorhombic crystal structure for NV ceramics. Field emission scanning electron microscopy (FE-SEM) shows distinguishable regular-shaped grains with clear grain boundaries. The dielectric and electrical properties of NV ceramics are investigated in the polymorphic R and S- orthorhombic phase. The structural transitions due to change in crystal symmetry is analyzed from the dielectric measurement and accompanied by dielectric anomaly at around 400 ∘C in temperature dependent dielectric characteristics. All the frequency dependent dielectric and electric properties are analyzed above the transition temperature i.e. in 400–520 ∘C (R and S polymorphic phase). The existence of typical negative temperature coefficient resistance (NTCR) behavior confirms by complex impedance study. The detailed investigation of Nyquist plots suggest that grain-resistance (Rg) and grain-boundary resistance (Rgb) are strongly affected by both the applied temperature and V-content in the samples.