Spectroscopic properties of Cr3+ ions in nanocrystalline glass–ceramic composites

Luminescence properties of Cr³⁺ ions in a silica-based precursor glass, and in fabricated optically transparent glass-based nanocrystalline composites, have been investigated. The luminescence spectra of the precursor glass revealed a wide range of crystal fields and showed the ⁴T₂–⁴A₂ broadband emission of Cr³⁺ ions in a weak crystal field, combined with ²E–⁴A₂ emission characteristic for Cr³⁺ ions in a strong crystal field. Glass–ceramic nanocomposites, with gallium oxide nanocrystals nucleated in a host glass matrix, indicated the prevailing contribution of the crystal-like ²E–⁴A₂ emissions (R-lines) of Cr³⁺ ions in a strong crystal field. The low-temperature studies demonstrated that the fluorescence of Cr³⁺ ions could be altered from sharp R-lines of the ²E–⁴A₂ transition, below 70 K, to a combination of R-lines and their sidebands, above 70 K. Our results indicate that, in the developed glass–ceramic nanocomposites, most of the Cr³⁺ ions have migrated from the host glass matrix to the nucleated gallium oxide nanocrystalline phase.