Evaluation of thermodynamics, formation energetics and electronic properties of vacancy defects in CaZrO3

Syed Muhammad Alay-E-Abbas,Stefaan Cottenier,Safdar Nazir,Ali Shaukat

doi:10.1038/s41598-017-08189-2

Abstract

Using first-principles total energy calculations we have evaluated the thermodynamics and the electronic properties of intrinsic vacancy defects in orthorhombic CaZrO3. Charge density calculations and the atoms-in-molecules concept are used to elucidate the changes in electronic properties of CaZrO3 upon the introduction of vacancy defects. We explore the chemical stability and defect formation energies of charge-neutral as well as of charged intrinsic vacancies under various synthesis conditions and also present full and partial Schottky reaction energies. The calculated electronic properties indicate that hole-doped state can be achieved in charge neutral Ca vacancy containing CaZrO3 under oxidation condition, while reduction condition allows to control the electrical conductivity of CaZrO3 depending on the charge state and concentration of oxygen vacancies. The clustering of neutral oxygen vacancies in CaZrO3 is examined as well. This provides useful information for tailoring the electronic properties of this material. We show that intentional incorporation of various forms of intrinsic vacancy defects in CaZrO3 allows to considerably modify its electronic properties, making this material suitable for a wide range of applications.

Highlights

The alkaline-earth metal zirconate ceramic materials (AZrO3, where A: Ca, Sr and Ba) are a versatile class of solid materials which have attracted a renewed research interest owing to their potential utilization in electrical, electronic and optical devices[1,2,3]
For studying the chemical stability of pristine CZO, we have computed the limits of atomic chemical potentials (ΔμX ≤ 0) by assuming that the chemical potential of an isolated atom of species
V28 ×O2 2c ×on 2tasuinpienrgcell we found that the presence of occupied states in conduction band minimum (CBM) persists for charge neutral V8O2 clustering in CZO and is independent Zr8O16 layers

Summary

Introduction

The alkaline-earth metal zirconate ceramic materials (AZrO3, where A: Ca, Sr and Ba) are a versatile class of solid materials which have attracted a renewed research interest owing to their potential utilization in electrical, electronic and optical devices[1,2,3]. Doped CZO or CZO containing intrinsic vacancy defects are promising candidates for achieving proton conductivity under hydrogenated or wet atmosphere at high temperatures[19]. To this end, In2O3-doped CZO has been thoroughly investigated owing to its higher mechanical and chemical stability and a sufficiently high degree of proton www.nature.com/scientificreports/. The motivation for present study is further strengthened by the fact that tuning the electronic transport properties of CZO by manipulating vacancy defects has not been carried out so far To this end, we employ the full-potential linearized augmented plane-wave (FP-LAPW) method within the framework of DFT for investigating the influence of vacancy defect on the electronic structure of CZO. It is expected that the detailed study of vacancy defects and clustering of charge neutral O vacancies reported in this work may stimulate future experimental studies to identify and use non-stoichiometric CZO for advanced device applications

Methods

Results

Conclusion