Ab initio study of hydrogen diffusion in zirconium oxide

Abstract

Hydrogen diffusion in monoclinic and tetragonal zirconium oxides has been studied by electronic state calculations. In both structures, the optimized hydrogen site lies near the center of a distorted fluorite structure. The activation energy was calculated to be 120-200 kJ/mol, which is similar to experimentally measured values. The effects of compressive stress, alloying elements, and oxygen defects are considered individually. Compressive stress reduces the hydrogen diffusion coefficient by 40%/GPa. Oxygen defects and substituted Fe and Cr are thought to act as trapping sites for hydrogen, which probably reduces hydrogen diffusion in zirconium oxide.

3D-characterization of deuterium distributions in zirconium oxide scale using high-resolution SIMS

“…All the deuterium concentrations are normalised by the concentration at the outer surface, Cs. Fitting to this equation yields diffusion coefficients of about 10 -20 m 2 /s at 360 °C, very close to previous experimental results that lie between 10 -18 and 10 -21 m 2 /s [38][39][40][41]. Our results show that the pre-transition sample Z4-5 (61 days corrosion time) has a higher deuterium diffusion coefficient of 9.1 ± 0.2 × 10 −20 m 2 /s than that in sample Z4-9 (106 days corrosion time) of 5.4 ± 0.2 × 10 −20 m 2 /s.…”

InAs FinFETs Performance Enhancement by Superacid Surface Treatment

“…As reported, oxides are notorious for fast diffusion of hydrogen [18]. Although metal gate was deposited on ZrO2 above the channel, hydrogen ions (H + ) can first diffuse vertically in the ZrO2 layer in the gap between gate and source (drain), which was not covered by Ni, then diffuse laterally under the Au/Ni gate through ZrO2 rendering reactivation of H + with In2O3 at the ZrO2/InAs interface.…”

Continuum model for hydrogen pickup in zirconium alloys of LWR fuel cladding

“…Raman spectroscopy measurement revealed that the stress varies cyclically and can be as large as several GPa 7 . DFT calculations found that under 1GPa compressive stress hydrogen diffusion coefficient in tetragonal ZrO 2 is only about 60% of the coefficient without stress at 600 K 15 . It is worth noting that there is also literature arguing that the diffusion of hydrogen through the barrier oxide layer is not the rate-limiting step 21,22 .…”

“…Besides the oxide morphology, additive elements (e.g., Fe, Cr, Nb, Sn and Ni) in different Zr alloys have substantial effects on the H pickup fraction. These elements may either behave like trapping sites and directly decrease the hydrogen diffusivity in the oxide 14,15 , or they may form second phase precipitates that have been hypothesized to be a preferred path for hydrogen migration or a source for pores or cracks formation [16][17][18] . Due to the lattice mismatch between Zr oxide and metal, high compressive stress is generated in the oxide near the interface 19,20 .…”