Study of structural, electrical, and photoluminescent properties of SrCeO3 and Sr2CeO4

Dharmendra Yadav,Upendra Kumar,Shail Upadhyay

doi:10.1007/s40145-019-0320-x

Abstract

Phase pure powders of SrCeO3 and Sr2CeO4 have been synthesized by calcination at 1000 °C for 14 h via solid state ceramic route. Ceramics/pellets of these samples have been obtained by sintering at 1200 ℃ for 12 h. The Rietveld refinement of X-ray diffraction (XRD) pattern of sintered powders confirmed orthorhombic structure of both the samples with space group Pnma and Pbam for SrCeO3 and Sr2CeO4, respectively. Scanning electron microscopic (SEM) studies indicated that both the compounds have dense microstructure, but morphology and size of the grains are different. The impedance spectroscopy technique has been employed to study the relaxation phenomenon. DC conductivity of the samples has been measured in the temperature range of 200–600 ℃ to understand the conduction mechanism. The activation energy for relaxation (Erelax) and DC conduction (Econd) are found to be the same for both the compounds. Based on the numerical value of activation energies, relaxation and conduction mechanism in both the samples are attributed to migration of doubly ionized oxygen vacancies (Vo••). Photoluminescence technique has been employed to confirm the existence of oxygen vacancies. These studies have indicated that migration of oxygen vacancies in Sr2CeO4 is occurring mainly along a and c direction, i.e., via perovskite cells. Further, the present work has clearly indicated that besides optical properties, electrical properties of Sr2CeO4 are also interesting and can be utilized for various applications such as oxide ion conduction electrolyte in solid oxide fuel cells (SOFCs).

Highlights

In the last two decades, perovskite oxide SrCeO3 has attracted considerable attention due to its potential applications in fuel cell, hydrogen sensor, H2–D2 gas cell, etc. [1,2,3,4]
The first step weight loss observed in the temperature range of 30–100 °C may be due to evaporation of remaining acetone or moisture adsorbed on the surface of the particles of the reactants
The second and main weight loss step recorded in the temperature range of 800–970 °C is assigned to the expulsion of CO2 gas during reaction between SrCO3 and CeO2 according to Eqs. (1) and (2): SrCO3 + CeO2 → SrCeO3 + CO2 (1)

Summary

Introduction

In the last two decades, perovskite oxide SrCeO3 has attracted considerable attention due to its potential applications in fuel cell, hydrogen sensor, H2–D2 gas cell, etc. [1,2,3,4]. Eu3+ doped Sr2CeO4 phosphors emitting white light (by combining blue, green, and red emissions) have potential applications in the fields of lamps and display devices under 280 nm excitation, and in the field of LEDs under near UV (350 nm) excitation [28,29,30]. It has been found from a thorough literature survey that only one or two published results are available on investigations of the electrical properties of Sr2CeO4. It was considered worthwhile to synthesize SrCeO3 and Sr2CeO4 under identical experimental conditions and compare their structural, electrical, and photoluminescent properties

Experimental

Results and discussion

By DC conductivity measurements

Conclusions