Maxwell-Wagner Relaxation in Ca-, Sm- and Nd-doped Ceria

Rida Ahmed,1

Shuting Wang,1

Sajid ur Rehman,2

Jie Sun,3

Jin Wang,1  

Renjun Si,1

Ankang Zhu,4

Yi Yu,1

Qiuju Li1 

Chunchang Wang1,5*Email

Laboratory of Dielectric Functional Materials, School of Physics & Material Science, Anhui University, Hefei, 230601, China

2 High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, Anhui, China.

3 State Key Laboratory of ASIC & System, School of Microelectronics, Fudan University, Shanghai 200433, China

4 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China

5 State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China

Abstract

Doped ceria, i.e. Ce1-xMxO2-δ with M being dopant metal, has been a focus of great attention for SOFCs due to their high oxygen conduction. In the past literature, the dielectric relaxations in these materials have been ascribed to be caused by defect associates (MCeʺ-Vö ) possessing different MCeʺ and Vö  distances. But we believe that with changing measurement and analysis techniques, it is necessary to invest our time to re-examine the already reported materials and take a detailed investigation of the underlying phenomenon behind their dielectric relaxations again. Thus, we have used solid-state reaction to prepare Ce1-xMxO2-δ with M=Ca, Sm, and Nd in x=0.1, 0.2, and 0.3 ratios, respectively. The as-prepared and post annealed samples were tested for dielectric properties from 300-1080 K with varying frequencies. The low-temperature relaxation (R1) was argued to be a Maxwell-Wagner relaxation caused by humidity sensitivity. The high-temperature relaxation (R2) was ascribed to be caused by the hopping motion of oxygen vacancies. This fact was also supported by a detailed analysis of impedance spectra. While according to the previous reports, this relaxation is because of the oxygen-vacancy-dopant defect pair.

Maxwell-Wagner Relaxation in Ca-, Sm- and Nd-doped Ceria