Pressure-induced structural evolutions and electronic properties of Eu³⁺ and Pr³⁺ doped yttrium oxide crystals: a...

Rare-earth-doped yttrium oxide (Y₂O₃) is a promising optoelectronic material due to its outstanding optical characteristics, including the efficient red emission of Eu³⁺ and the lattice-sensitive luminescence of Pr³⁺. The crystal lattice and structural information have aroused widespread interest. However, clarifying the structural evolution and local structures in doped systems under high pressure remains challenging. In this work, we systematically investigate the structural evolution and electronic properties of Y₂O₃:Eu³⁺ and Y₂O₃:Pr³⁺ under the pressure range of 0-40 GPa. The ground-state structures are identified for the first time. Eu³⁺ and Pr³⁺ substitute Y³⁺ sites with a doping concentration of 3.125%. At ambient pressure, the structure of Y₂O₃:Eu³⁺ exhibits a trigonal structure with the R3̄ space group while Y₂O₃:Pr³⁺ exhibits a monoclinic configuration with the P2 space group. LDA + U + SOC calculations reveal narrowed band gaps of 1.884 and 3.326 eV for Y₂O₃:Eu³⁺ and Y₂O₃:Pr³⁺, respectively, indicating an insulator-to-semiconductor transition. Under pressure, Y₂O₃:Eu³⁺ shows higher sensitivity in lattice and electronic properties than Y₂O₃:Pr³⁺. Pressure enhances intrinsic 4f-electron differences, leading to divergent evolution trends. The 4f configuration serves as a key controller of high-pressure behavior. These findings could not only provide important information for further investigations of rare-earth-doped systems, but also help to gain more insights into designing a new generation of laser materials under extreme conditions.