Influences of Ce3+ dosage, NH4Cl flux, and post-treatment on the structure and luminescence properties of Ce-activated La–Si–O–N for laser lighting

Abstract

The emerging laser-driven phosphor-converted white laser diodes (w-LDs) demand highly efficient and thermally stable color converters. To this end, the Ce3+ luminescence in the rekindled La–Si–O–N host, and the impacts of NH4Cl flux and post-processing are investigated systematically. On the basis of the XRD results, well crystalline Ce3+-doped La5Si3O12N and LaSiO2N are obtained at 1600 °C for 5 h and 1500 °C for 4 h, respectively. Impressively, the representative La5Si3O12N:0.04Ce3+ and LaSiO2N:0.03Ce3+ exhibit a broad excitation band from 240 nm to 400 nm, peaking at around 360 nm, which is well matched with emission from near-UV (n-UV) chip. Under excitation by a n-UV laser, the La5Si3O12N:0.04Ce3+ and LaSiO2N:0.03Ce3+ produce bright blue light in a wide emission band from 360 nm to 550 nm. The CIE chromaticity diagram reveals the tunability of the hue of these phosphors. The quenching temperature is determined to be 396 K and 429 K for La5Si3O12N:0.04Ce3+ and LaSiO2N:0.03Ce3+ respectively, indicating superior thermal stability. The addition of 3 wt% NH4Cl flux much enhances the emission intensity of both La5Si3O12N:0.04Ce3+ and LaSiO2N:0.03Ce3+. Furthermore, the post-treatments markedly improve the luminescence properties by increasing the crystallinity, reducing the surface defect, and changing the morphology. Therefore, it is believed that the present work has promising applications in LD lighting and promoting the development of laser display.