Search

Single phase NaNb 1 − x Mn x O 3 (NMn) with x = 0.00−0.06 ceramics were synthesized using solid state reaction technique at 1150 °C sintering temperature. The Rietveld refinement of XRD patterns of NMn ceramics confirms the orthorhombic phase symmetry with P b m a space group. The field emission scanning electron microscopy (FE-SEM) reveals that grains become denser and larger with doping. The dielectric constant (ϵ ′) and tangent loss (tan δ) study has been done at room temperature to 500 °C over a wide frequency in both cooling and heating mode. The anomaly at high temperature region in temperature dependent dielectric constant (ϵ ′) plot in both thermal cycle attributes to the P(AFE)-R(AFE) polymorphic phase transition. The relaxor nature of the studied samples strongly depends on dopant concentration and applied field. The impedance analysis reveals negative temperature coefficient of resistance (NTCR) behaviour of material. The Nyquist study suggests the non-Debye characteristic of the dielectric relaxation in NMn ceramics. • Rietveld refinement confirms the single phase formation of NMn samples. • Anomaly in ɛ vs. T plot suggests the P-R polymorphic phase transition. • High value of ɛ and low value of tan δ obtained for Mn modified NN samples. • Non-Debye type relaxation and NTCR nature confirmed from impedance study. [ABSTRACT FROM AUTHOR]

The lead-free polycrystalline NaNb 1− x V x O 3 (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 (R g) and grain-boundary resistance (R gb) are strongly affected by both the applied temperature and V-content in the samples. [Display omitted] • The polycrystalline NV samples are prepared by solid state reaction technique. • The dielectric characteristics of NV system are studied in R and S-phase. • The effect of V- ion on the grain growth is clearly noticeable. • In studied samples, NV2 composition gives maximum value of ε′ ~3.8 × 103 at 520 °C. • Impedance spectroscopic studies reveal the NTCR behavior of NV ceramics. [ABSTRACT FROM AUTHOR]