Raman spectroscopy of zirconium hydride

The characterization of zirconium hydride is important in the nuclear industry because of the hydrogen-induced embrittlement of Zircaloy cladding and its use as a neutron moderator. This paper introduces the use of Raman spectroscopy for the characterization of zirconium hydride. First-principles density functional theory (DFT) calculations were used to predict the Raman spectra of ζ-ZrH _0.5, γ-ZrH, δ-ZrH _1.5, δ-ZrH _1.66, and ε-ZrH ₂ with all their predicted symmetries; ζ-ZrH _0.5 ( P3m1, R 3 ¯ m, C2/m, Cm, Cmmm, and Pn 3 ¯ m); γ-ZrH ( P222, Ccce, and P4₂/mmc); δ-ZrH _1.5 ( P 4 ¯ m2, P4₂/mcm, Fmmm, Pn 3 ¯ m, Ibam, P2/c, PI, and P4₂/nnm); δ-ZrH _1.66 ( Fm 3 ¯ m); and ε-ZrH ₂ ( Fm 3 ¯ m, R 3 ¯ m, and I₄/mmm). Two samples of Zircaloy-4 containing 133 wt ppm and 360 wt ppm hydrogen were characterized by Raman spectroscopy, showing two signal lines at 215 cm ⁻¹ and 1,187 cm ⁻¹, which were assigned to the presence of δ-ZrH _1.66. These signals had a good spatial correlation with visible hydride precipitates in Raman spectroscopy images. This work provides the basis for the characterization of all possible zirconium hydride compositions and structures using Raman spectroscopy.