High-Pressure Synthesis, Structural, and Optical Properties of Layered Cerium Borate CeMgB₃O₇

The present work reports a novel borate layered CeMgB₃O₇ crystal with an orthorhombic lattice (Cmme) as determined by single-crystal X-ray diffraction, which was synthesized through high-pressure solid-state metathesis reaction, marking the first successful preparation of that type of structure under high pressure and high temperature. Using multimodal characterization techniques, including in situ high-pressure synchrotron radiation X-ray diffraction and Raman spectroscopy, the exceptional structural stability of CeMgB₃O₇ was confirmed up to 34 GPa. X-ray photoelectron spectroscopy measurements and the photoluminescence (PL) spectroscopy further identified a novel pathway for achieving near-infrared emission in Ce-based materials, highlighting the potential of defect engineering to directly activate luminescent centers within the host lattice in CeMgB₃O₇. The high-pressure PL spectroscopy indicates that applied pressure effectively modulates the crystal field splitting degree in [CeO₁₀]^17-, imposing a direct and tunable influence on its intrinsic luminescence. These findings advance the understanding of luminescence mechanisms in Ce-based systems and offer new insights for the future design of luminescent materials.