Joint experimental and theoretical study of bulk Y2O3 at high pressure

Size-Dependent High-Pressure Behavior of Pure and Eu3+-Doped Y2O3 Nanoparticles: Insights from Experimental and Theoretical Investigations

“…In order to undertake the structural characterization of the Y 2 O 3 -37 nm nanocrystals, we performed synchrotron-based HP-XRD measurements ( Figure 1 ). A comparison of Figure 1 a,b with HP-XRD measurements of the bulk Y 2 O 3 [ 19 ] evidences a very similar behavior of Y 2 O 3 -37 nm and Y 2 O 3 -Bulk samples. As pressure increases the peaks of the C-type phase in Y 2 O 3 -37 nm tend to displace to higher angles, indicating a decrease in the unit-cell volume.…”

“…Thus, as mentioned for Y 2 O 3 -Bulk, the peaks that appear at 13.3, 15.2, and 18.5 GPa may initially belong to the B-type phase, indicating a mixture between the B- and C-type phases. At even higher pressures there is a PT to the A-type phase in Y 2 O 3 -37 nm as in Y 2 O 3 -Bulk [ 19 ]. These results regarding the pressure-induced C-B-A PT sequence in Y 2 O 3 -37 nm on increasing pressure are further confirmed by our RS measurements (later commented).…”

“…This result confirms the A-B PT in Y 2 O 3 -37 nm nanocrystals on downstroke. As in bulk material [ 19 ], the B-type phase is retained at ambient conditions in the Y 2 O 3 -37 nm nanocrystals as evidenced by the large number of Raman-active modes. The observation of a large number of Raman-active modes in recovered Y 2 O 3 -37 nm nanocrystals is in agreement with the RS spectrum of Y 2 O 3 nanocrystals (~70 nm) recovered from 19 GPa studied by Dilawar et al [ 47 ], where a broad band, corresponding to a partial amorphous sample, and a large number of Raman modes, likely corresponding to the monoclinic phase, were observed.…”

“…Ab initio total-energy calculations at 0 K for the C-, B-, and A-type phases of bulk Y 2 O 3 were performed within the Density Functional Theory (DFT) [ 34 ] framework with the Vienna Ab-initio Simulation Package (VASP) [ 35 , 36 ], as already reported in ref. [ 19 ]. The pseudopotential method and the projector augmented waves (PAW) scheme [ 37 , 38 ] were used with the plane-wave basis set extended up to an energy cutoff of 520 eV.…”

“…Our measurements in pure and doped Y 2 O 3 nanoparticles evidence that the behavior of nanoparticles under compression depends on the average particle size. Nanoparticles with an average particle size of ~37 nm show the same pressure-induced phase transition (PT) sequence (C-B-A) on upstroke and (A-B) downstroke as the bulk sample [ 19 ]. This is in contrast with what has been published in many previous works [ 20 , 21 , 22 , 23 , 24 , 25 ].…”