Tunable optical emissions of Eu3+ ions enabled by pressure-driven phase transition in ZnO

We present an extensive investigation on the properties of Eu 3+ optical emissions associated with deformation of ZnO host applying an external hydrostatic pressure, combining in situ synchrotron X-ray diffraction and photoluminescence spectroscopy with first-principles calculations. A pressure-induced phase transition from the hexagonal wurtzite to the cubic rocksalt structure near 10 GPa is accompanied by complete quenching of the 5 D 0 → 7 F J emissions near the threshold, followed by a partial but reproducible recovery at higher pressures, likely associated with the emergence of structural disorder. Concurrently, as the crystal field strength increases, the Stark components of the emissions exhibit a systematic redshift (∼0.40 ± 0.02meV/GPa) and pressure-induced broadening (∼0.55 ± 0.02 meV/GPa). The first-principles calculations support the observed pressure-induced shifts in the Eu-4f states and emphasize the influence of lattice symmetry on their electronic environment. These findings establish hydrostatic pressure as a powerful tool for tuning rare-earth optical emissions through symmetry-driven and local-environment modifications, laying the foundation for pressure-engineered photonic functionalities and luminescent devices. • Pressure-driven wurtzite-to-rocksalt transition modulates Eu 3+ luminescence in ZnO. • The structural transition initiates at ∼5.8 GPa, with cubic dominance above 10GPa. • Redshift and Stark splitting due to enhanced lattice symmetry and crystal field. • DFT reveals symmetry-dependent reshaping of electronic states under compression. • Lattice symmetry control governs RE optical activity under extreme conditions.