Dielectric relaxation and conduction mechanism of NaMgPO4 compound

Abstract

The polycrystalline NaMgPO4 ceramic, synthesized via a high-temperature solid-state reaction route, has been characterized by using different experimental procedures. The X-ray powder diffraction confirmed the phase formation of the synthesized compound in the orthorhombic phase. It assumed an olivine-type structure made up of corners linked between tetrahedral PO4 and octahedral NaO6 and MgO6 groups. Infrared and Raman spectroscopies confirmed the presence of PO[Formula: see text] groups. Local structure and chemical bonding between MgO6 octahedral and PO[Formula: see text] tetrahedral groups investigated by diffusion Raman is the feature in the phase transition at [Formula: see text] 693 K. The temperature dependences of the real [Formula: see text] and imaginary [Formula: see text] parts of dielectric permittivity show a distribution of relaxation times. From Nyquist plots, the presence of grain and grain boundary effect in the material is noticed. The impedance spectroscopy measurement showed a non-Debye-type process. From the impedance data, the determined grain resistance reduces with increment of temperature showing negative temperature coefficient of resistance (NTCR)-type nature of the material which also confirmed from conductivity analysis. The temperature dependence of [Formula: see text] reveals an Arrhenius-type behavior with two activation energies, 0.98 eV in region I and 0.67 eV in region II. Studied sample’s conduction is assured by Na[Formula: see text] ions’ hopping in tunnels and its mechanism was discussed.

Keywords

• Sodium-magnesium orthophosphate
• Raman
• phase transition
• NSPT model
• sodium-ion conductivity