Effect of zinc doping on electrical properties of LaAlO3 perovskite

Anastasia V Egorova,Artem A Kabanov,Yelizaveta A Morkhova,Irina E Animitsa,Ksenia G Belova

doi:10.15826/chimtech.2020.8.1.03

Abstract

New solid solution with the general formula of LaAl1-xZnxO3-1/2x was prepared by a solid-state reaction route. According to XRD, the crystal structure of LaAlO3 is rhombohedral, while the solid solution possesses cubic symmetry. Homogeneity region of the solid solution LaAl1-xZnxO3-1/2x was narrow and limited to the maximum concentration of 5 mol. %. Computer simulations using crystalochemistry and density functional theory approaches showed that LaAlO3 has high energy barriers for O2–-ion transport (2.79 eV). These results are in good agreement with the low values of electrical conductivity obtained experimentally. The electrical conductivity of LaAl1-xZnxO3-1/2x was measured by impedance spectroscopy in the temperature range of 200–1000 °C. The partial substitution of Al3+ by Zn2+ was found to increase the electrical conductivity by ~2 order of magnitude. The electrical conductivity of doped phase LaAl0.95Zn0.05O2.975 as a function of oxygen partial pressure was measured, and the partial contributions (oxygen-ionic and electronic) were determined. It was found that the sample has mixed ionic and p-type electronic conductivity, while the electronic contribution increases with the rise of the temperature.

Highlights

During the past few decades, the perovskites have been used in various electrochemical devices and their properties have been well described
It should be noted that the main substitutions are performed for the La-sublattice, and in this case the alkaline earth metal is the dopant, which reduces the chemical resistance of the material
In this study we used ZnO as a dopant for several reasons: i) as an acceptor dopant, divalent Zn2+ increases the concentration of oxygen vacancies in the perovskitelattice; ii) in addition, due to the stable oxidation state, the doping will not lead to an increase in the electronic conductivity; iii) zinc belongs to the IIB group in the Periodic Table, it is not an alkaline earth element, the presence of which impairs chemical stability

Summary

Introduction

During the past few decades, the perovskites have been used in various electrochemical devices and their properties have been well described These materials are promising electrolyte systems for solid oxide fuel cells (SOFCs). It should be noted that the main substitutions are performed for the La-sublattice, and in this case the alkaline earth metal is the dopant, which reduces the chemical resistance of the material. In this study we used ZnO as a dopant for several reasons: i) as an acceptor dopant, divalent Zn2+ increases the concentration of oxygen vacancies in the perovskitelattice; ii) in addition, due to the stable oxidation state, the doping will not lead to an increase in the electronic conductivity; iii) zinc belongs to the IIB group, it is not an alkaline earth element, the presence of which impairs chemical stability. The investigations of electrical properties of LaAlO3 and Zn-doped at the B-site LaAlO3 were performed

Experimental

Results and Discussion

Electrical measurements

Conclusions