Influence of Mn-doping on the structure, high-temperature dielectric, and conductive properties of NaNbO3 ceramics

Single phase NaNb1−xMnxO3 (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 Pbma 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.