The Influence of Interphases on the Macro-Characteristics of Luminescent Oxide Glass-Ceramics: Experimental and...

A comprehensive experimental and computational study of interphases in oxide glass-ceramics is presented. The main objectives of the study were to understand the mechanisms of interphase formation, elucidate the composition and structure of interphases, and reveal the influence of interphases on macro-characteristics of the studied glass-ceramics. The series of boron oxide-based glasses of (mNa₂O-nP₂O₅-pB₂O₃-xPbO):yEu₂O₃ and (mLi₂O-pB₂O₃-xV₂O₅):yEu₂O₃ compositions incorporated with luminescent micro/nanoparticles of NaCa(BO₃):Eu, Ca₃Eu₂(BO₃)₄, and LaVO₄:Eu crystals have been prepared. The experimental studies comprised scanning electron microscopy, X-ray diffraction, optical diffuse reflection, and photoluminescence. Computational methods (molecular dynamics and density functional theory) have also been used to determine the energy structure, composition, and partial density of the electronic states of atoms associated with the interphase layers. The calculations revealed the formation of interphase layers with a thickness of ∼3 nm and showed their influence on the optical absorption spectra and the band gap of the glass-ceramics. These results were confirmed by experimental measurements. The luminescence caused by radiative transitions in the Eu³⁺ ions changes in a sequence of glass → crystal → glass-ceramic samples. An analysis of these changes allowed the determination of the interphase layers' influence on the intensity and the emission spectra of the studied materials. The photoluminescent results confirmed the prospects of Eu³⁺ ions as effective luminescent probes to study interphase layers in oxide glass-ceramics. It was found that variations in the composition of the glasses, in the content of Eu³⁺ ions, and in the content and type of the filler particles (all of the factors noted are related to interphase formation) lead to changes in chromaticity characteristics. This result showed the prospects of the studied glass-ceramics for use as luminescent converters in white light-emitting diodes.