Lattice dynamics of yttria: A combined investigation from spectrum measurements and first‐principle calculations

C‐type Y2O3 ceramics (relative density ~94%) were prepared at 1500 °C for 2 hours with 1% wt. ZnO as sintering aid. The cell parameters of Y2O3 from Rietveld refinements are a = 10.6113(1) Å, V = 1194.8(1) Å3. The vibrational modes / lattice dynamics of Y2O3 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 (fexp = 1.023ftheo, R2 = 0.9999) between frequency from calculations (ftheo) and that from measurements (fexp) is observed. Accordingly, the corrected frequency (fcor) of vibrational modes, phonon band structure, and density of phonon states (DOPS) of Y2O3 are presented, in which, the frequency of phonons of Y2O3 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 ftheo ≥292.5 cm−1 (fcor ≥299.2 cm−1) are dominated by the vibrations of O2− (light atom vibrations) and the vibrational modes with ftheo ≤239.0 cm−1 (fcor ≤244.5 cm−1) are dominated by the vibrations of both Y3+ and O2− (co‐vibrations). The three modes Tu(7) at 301.6 cm−1, Tu(10) at 333.7 cm−1, and Tu(12) at 369.7 cm−1 of Y‐O stretch vibrations dominate the phonon dielectric constant and dielectric loss of Y2O3 with more than 85% contributions.