Doping induced phase stabilization and electronic properties of alkaline earth metal doped zirconium (IV) oxide: A first principles study

Abstract

The role of divalent dopant cations such as Ca and Mg in phase stabilization of ZrO2 has been demonstrated experimentally, with Mg emerging as a crucial dopant ion because of its ability to enhance the photocatalytic properties of ZrO2. To provide a theoretical basis for these experimental observations, the modifications of the crystal and electronic structure of the monoclinic phase of zirconia, m-ZrO2, upon doping with Mg have been studied at the atomic level using Density Functional Theory method. Additionally, the effect of dopant ionic radius on the electronic properties has been demonstrated by doping with Ca, which is isoelectronic with Mg. On 6.25 % doping, a structural distortion of the monoclinic crystal structure towards a tetragonal structure is observed. Additionally, the Density of States of doped m-ZrO2 exhibits the characteristics of t-ZrO2 in the Zr d orbitals in the unoccupied states and O unoccupied states emerge upon creation of an O vacancy in Mg/Ca doped m-ZrO2. The calculated band gap of m-ZrO2 is 3.6 eV. Upon doping there is a shift of the Fermi energy towards the valence band maximum.