Structural properties, dielectric relaxation and impedance spectroscopy of NASICON type Na$_{3+x}$Zr$_{2-x}$Pr$_{x}$Si$_2$PO$_{\rm 12}$ ceramics

TL;DR

This study explores the dielectric and impedance properties of Pr-doped NASICON ceramics, revealing non-Debye relaxation, grain boundary effects, and potential for charge storage applications.

Contribution

It provides a detailed analysis of the dielectric relaxation and conduction mechanisms in Pr-doped NASICON ceramics, highlighting their suitability for charge storage devices.

Findings

Non-Debye dielectric relaxation observed across samples.

Presence of grain and grain boundary relaxation peaks.

CBH conduction mechanism confirmed by power law fitting.

Abstract

We investigate the dielectric and impedance spectroscopic investigation of Pr-doped NASICON type Na$_{3+x}$Zr$_{2-x}$Pr$_{x}$Si$_2$PO$_{\rm 12}$ ($x=$ 0.05--0.2) samples as a function of temperature and frequency. The Rietveld refinement of x-ray diffraction patterns confirms the monoclinic phase having C2/c space groups for all the samples. The scanning electron microscopy shows the granular-like structure and energy dispersive x-ray analysis confirms the desired compositions. The temperature (90--400~K) and frequency (20 Hz-2 MHz) dependence of electric permittivity are explained using Maxwell-Wagner-Sillars (MWS) polarization and space charge polarization mechanisms. The dielectric relaxation shows nearly equal activation energy for all the samples with a non-Debye type of relaxation in the measured temperature range. The complex impedance analysis shows the presence of broad grain and grain boundary relaxation peaks. The stretched exponent analysis of electric modulus using the Kohlrausch-Williams-Watts (KWW) function further confirms the non-Debye type of relaxation. Moreover, scaling analysis of the electric modulus shows a similar type of relaxation for all the samples. The {\it a.c.} conductivity data are fitted using modified power law, where the temperature dependence of exponent ($s$) confirms the correlated barrier hopping (CBH) type conduction for all the samples. Our results indicate that the Pr doped NASICON samples are potential candidates for charge storage devices due to their large electric permittivity.