Lattice Engineering Modulates the Optical Bandgap and Near-Infrared Properties of BaSnO₃:Cr³⁺ Phosphors

This study successfully synthesized a series of BaSnO₃:xCr³⁺ phosphors via a high-temperature solid-state method. Through lattice engineering strategies, effects of Cr³⁺ doping on crystal structure, optical bandgap, and near-infrared luminescence properties of BaSnO₃ were systematically investigated. Diffuse reflectance spectroscopy (DRS) revealed that Cr³⁺ doping significantly reduced the effective optical bandgap; the indirect bandgap was adjusted to 2.82 eV. Spectroscopic studies indicated that the broad excitation band between 320 and 450 nm originates from ⁴A₂ → ⁴T₁(⁴P)transition, whereas the characteristic absorption between 550 and 800 nm corresponds to Cr³⁺ d-d transitions (⁴A₂ → ⁴T₂). Under 350-nm UV excitation, these phosphors exhibited near-infrared emission with a central wavelength at 900 nm and a full width at half maximum (FWHM) of approximately 104 nm, attributed to Cr^{3+ 2}E_g → ⁴A₂ radiative transition. This work demonstrates an effective strategy for modulating band structure and luminescent properties of perovskite oxides through lattice strain engineering, providing both theoretical and experimental guidance for designing novel near-infrared luminescent materials.