Fe-doped effects on phase transition and electronic structure of CeO2 under compressed conditions from ab initio calculations

Karnchana Sathupun,Arnab Majumdar,Prayoonsak Pluengphon,Thiti Bovornratanaraks,Prutthipong Tsuppayakorn-aek,Komsilp Kotmool

doi:10.1007/s00339-021-04911-0

Abstract

Ab initio study of high-pressure phase transition and electronic structure of Fe-doped CeO2 with Fe concentrations of 3.125, 6.25, and 12.5 at% has been reported. At a constant-pressure consideration, the lattice constants and the volume of the supercell were decreased with an increasing concentration of Fe. The average bond length of Fe–O is lower than that of Ce–O. As a result, Fe doping induces the reduced volume of the cell, which is in good agreement with previous experiments. At high pressure (~ 30 GPa), it was found that the transition pressure from the fluorite to the cotunnite orthorhombic phase decreases at a higher concentration of Fe, indicating that the formation energy of the compound is induced by Fe-doping. Furthermore, compression leads to interesting electronic properties too. Under higher pressures, the bandgap increases in the cubic structure under compression and then suddenly plummets after the transition to the orthorhombic phase. The 3d states of Fe mainly induced the impurity states in the bandgap. In both the undoped and Fe-doped systems, the bandgap increased in the cubic phase at high pressure, while the gap and p-d hybridization decrease in the orthorhombic phase.

Highlights

Cerium oxide (CeO2) is an attractive material with various applications, mainly for automobile catalytic converters to decrease pollutants, as well as solid oxide fuel-cell technologies and optical equipment [1,2,3,4,5,6,7,8,9,10]
At high-pressure consideration, a phase transition from fluorite phase to cotunnite phase is calculated at 28.0 GPa with a volume reduction of 6.45% for undoped CeO2
The decrement of the transition pressure trend depends on the percentage of Fe. This is because the free energy of C eO2 systems is decreased at a high concentration of Fe-doping

Summary

Introduction

Cerium oxide (CeO2) is an attractive material with various applications, mainly for automobile catalytic converters to decrease pollutants, as well as solid oxide fuel-cell technologies and optical equipment [1,2,3,4,5,6,7,8,9,10]. C eO2 has been proposed to be a possible gate dielectric material in metal–oxide–semiconductor devices of the generation [25]. Several experiments, such as highpressure Raman spectroscopy, reported that the pressureinduced transition of CeO2 from cubic fluorite structure to orthorhombic PbCl2 structure occurs at around 31 GPa [12]. These results are very close to that investigated by energydispersive X-Ray diffraction with phase transition pressure of 31.5 GPa [13]. The structural and physical properties of the C eO2 doped with Fe have been investigated by previous studies [20,21,22,23,24]

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