Lattice dynamics of yttria: A combined investigation from spectrum measurements and first‐principle calculations
Chun‐Hai Wang, Wenhua Shu, Yuchang Qing, Fa Luo, Dongmei Zhu, Wancheng Zhou
Abstract
Abstract C‐type Y 2 O 3 ceramics (relative density ~94%) were prepared at 1500 °C for 2 hours with 1% wt. ZnO as sintering aid. The cell parameters of Y 2 O 3 from Rietveld refinements are a = 10.6113(1) Å, V = 1194.8(1) Å 3 . The vibrational modes / lattice dynamics of Y 2 O 3 were investigated using vibrational spectra (Raman and infrared reflection spectra) and first‐principle (DFT) calculations. Eight of the 22 predicted first‐order Raman modes and 12 of 16 predicted IR modes are observed and reliably assigned. For the observed vibrational modes, an excellent linearity ( f exp = 1.023 f theo , R 2 = 0.9999) between frequency from calculations ( f theo ) and that from measurements ( f exp ) is observed. Accordingly, the corrected frequency ( f cor ) of vibrational modes, phonon band structure, and density of phonon states (DOPS) of Y 2 O 3 are presented, in which, the frequency of phonons of Y 2 O 3 is ≤625.2 cm −1 (wavelength ≥16.0 μm) with a gap of 30.6 cm −1 from 486.0 to 516.6 cm −1 (wavelength 20.6 ‐ 19.4 μm) at room temperature. The modes with f theo ≥292.5 cm −1 ( f cor ≥299.2 cm −1 ) are dominated by the vibrations of O 2− (light atom vibrations) and the vibrational modes with f theo ≤239.0 cm −1 ( f cor ≤244.5 cm −1 ) are dominated by the vibrations of both Y 3+ and O 2− (co‐vibrations). The three modes T u (7) at 301.6 cm −1 , T u (10) at 333.7 cm −1 , and T u (12) at 369.7 cm −1 of Y‐O stretch vibrations dominate the phonon dielectric constant and dielectric loss of Y 2 O 3 with more than 85% contributions.