High-Temperature Dielectric Relaxation Behaviors in Mn3O4 Polycrystals.

Songwei Wang,Xin Zhang,Huaiying Zhou,Liguo Fan,Rong Yao

doi:10.3390/ma12244026

Abstract

High temperature dielectric relaxation behaviors of single phase Mn3O4 polycrystalline ceramics prepared by spark plasma sintering technology have been studied. Two dielectric relaxations were observed in the temperature range of 200 K–330 K and in the frequency range of 20 Hz–10 MHz. The lower temperature relaxation is a type of thermally activated relaxation process, which mainly results from the hopping of oxygen vacancies based on the activation energy analysis. There is another abnormal dielectric phenomenon that is different from the conventional thermally activated behavior and is related to a positive temperature coefficient of resistance (PTCR) effect in the temperature region. In line with the impedance analyses, we distinguished the contributions of grains and grain boundaries. A comparison of the frequency-dependent spectra of the imaginary impedance with imaginary electric modulus suggests that both the long range conduction and the localized conduction are responsible for the dielectric relaxations in the Mn3O4 polycrystalline samples.

Highlights

The relation between physical properties and microstructure is an important aspect for ceramic materials and is helpful for better understanding their electrical properties [1,2,3,4,5]
The positive temperature coefficient of resistance (PTCR) effect is characterized by an increase in resistance with temperature, which is in contrast to the thermally activated behavior in which resistance decreases with temperature
The PTCR effect of the donor-doped BaTiO3 was demonstrated by Heywang-Jonker model [7,8] and was attributed mainly to the donor dopants, which resulted in the difference of the resistances between the grain and grain boundary

Summary

Introduction

The relation between physical properties and microstructure (such as grains, grain boundaries, sample-electrode interfaces, and so on) is an important aspect for ceramic materials and is helpful for better understanding their electrical properties [1,2,3,4,5]. The PTCR effect of the donor-doped BaTiO3 was demonstrated by Heywang-Jonker model [7,8] and was attributed mainly to the donor dopants, which resulted in the difference of the resistances between the grain and grain boundary. We studied the microstructure-property relation of Mn3 O4 polycrystalline sample in the high temperature range (200–330 K) and demonstrate the comprehensive understanding of dielectric relaxation of Mn3 O4 ceramics by using dielectric and impedance spectroscopy. The relaxation at higher temperature is attributed to the PTCR effect, caused by the difference of the resistances between the grain and grain boundary. This work is helpful for understanding the dielectric relaxation behaviors in manganese oxides materials

Experimental

Results and Discussion

57 Hz131 Hz

Similar phenomena were shown

Conclusions