Exploring color tunable emission characteristics of Eu³⁺-doped La₂(MoO₄)₃ phosphors in the glass-ceramic form

The glass-ceramic form of phosphor materials can overcome the many serious issues of phosphor/silicone composite in commercial phosphor-converted LEDs and are considered as new-generation color converters. In this report, we have shown a novel approach of developing inorganic red phosphor [Eu³⁺:La₂(MoO₄)₃] in the glass-ceramic form based on lanthanum molybdate system. The ceramic form of the compound was found to have a glass transition temperature of 1002 °C, as confirmed by TGA and DSC studies. Further, XRD, FTIR and Raman studies also confirmed that the compounds prepared at 1050 °C are in glass-ceramic form, while those prepared at 750 °C are in ceramic form. Photoluminescence studies showed that both the ceramic and glass-ceramic forms of the phosphor are red color-emitting materials. However, the glass-ceramic forms have better color purity and more radiation transition probabilities. Further, the decay kinetics of both ceramic and glass-ceramic forms confirmed that only those Eu³⁺ ions which exist in the grain boundaries of the ceramics go inside the glass network structure upon heating the compound at or above the glass transition temperature. On the other hand, Eu³⁺ ions which exist at the La-site in the bulk of the particles are retained in the ceramic form in the glass-ceramic mixture.