Atomistic insight into the defect-induced tunable plasticity and electronic properties of tetragonal zirconia

Tetragonal zirconia (t-ZrO2) with exceptional properties is crucial in catalytic applications. Defects effectively enhance its electronic properties and plasticity, making t-ZrO2 a valuable material for high-efficiency industrial catalysts, and flexible electronic devices. In this study, we utilize first-principles calculations to compare the impact of vacancy defects and nitrogen doping on the structural and electronic properties of wide bandgap semiconductor t-ZrO2. Additionally, we analyze the tuned plasticity of t-ZrO2 by varying N-dopant and vacancy concentrations using molecular dynamics simulations and cyclic-nanoindentation tests. The estimation of energy release associated with plastic deformation is conducted using the Griffith energy balance model. Our study reveals significantly distinct electronic properties and plastic deformation maps in oxygen-deficient and N-doped t-ZrO2 compared to the perfect counterpart, where the defect nature dictates the band gap energy and plastic zone size. t-ZrO2_x exhibits a greater bandgap narrowing than t-ZrO2_xNx, resulting from increased atomic displacement, decreased free energy for plastic deformation, and enhanced plastic dissipated energy. Further-more, we demonstrate that electronic properties and the plasticity of t-ZrO2_xNx, including bandgap energy and energy release rate during cyclic-nanoindentation, are unable to compete with those of the small-bandgap counterpart t-ZrO2_x. Herein, t-ZrO2_x, x = 0.2 exhibits the highest plasticity and the smallest bandgap of 1.28 eV, contrasting with the 5.6 eV bandgap of perfect t-ZrO2. Thereby, t-ZrO2_x displays pronounced band gap tightening and enriched flexibility, providing it a favorable semiconductor for photoelectrochemical energy conversion (PEC) applications.

Automated summary

In this study, the impact of vacancy defects and nitrogen doping on the properties of tetragonal zirconia (t-ZrO2) was investigated. Oxygen-deficient t-ZrO2 showed a smaller bandgap and enhanced plasticity, while nitrogen-doped t-ZrO2 had a smaller bandgap but weaker plasticity. The results suggest that oxygen-deficient t-ZrO2 is a promising semiconductor material for photoelectrochemical energy conversion applications due to its smaller bandgap and higher plasticity.