High-Pressure Stability and Compressibility of Zircon-Type YV1–xPxO₄:Eu³⁺ Solid-Solution Nanoparticles: An X-ray Diffraction and Raman Spectroscopy Study

We probed the high-pressure response of the YV 1– x P x O 4:Eu 3+ ( x = 0, 0.5, 0.7, 1.0) solid-solution nanoparticles using angular dispersive synchrotron X-ray diffraction (XRD) and Raman techniques at room temperature. In situ diffraction results showed that the overall nanoparticles underwent an irreversible zircon-to-scheelite structural transformation. The transition pressures were ∼9.3, ∼12.1, ∼14, and ∼18.4 GPa for the YV 1– x P x O 4:Eu 3+ ( x = 0, 0.5, 0.7, 1.0) samples, respectively. Coupled with the zircon-to-scheelite transition features, it was proposed that the transition pressure was probably governed by the stiffness of VO 4 /PO 4 units in the solid solutions. This claim was verified by further Raman measurements, which revealed that the stiffness of VO 4 /PO 4 units was enhanced with increasing P contents. The structural refinements showed that the samples with comparable particle size (20–90 nm) became less compressible with increasing P content ( x = 0 → 0.7 → 1.0). However, the compressibility of the YV 0.5 P 0.5 O 4:Eu 3+ sample with smaller particle size (10–30 nm) was similar to that of the YV 0.3 P 0.7 O 4:Eu 3+ sample. The general compressibility behavior as a function of P content was ascribed to the special packing style related to the stiffness of VO 4 /PO 4 tetrahedra in zircon structure, and the higher surface energy contribution was responsible for the exceptional compressibility in the smaller nanoparticles.