Improvement of emission and thermal stability induced by selected occupation of Al3+ in Ba3Si6O12N2:Eu2+ phosphors

Abstract

Oxynitride Ba3Si6O12N2:Eu2+ phosphor can usually exhibit high color purity emission spectrum and outstanding thermal stability because of its rigid structure which can be widely used in WLEDs. With the aim of further optimizing the emission intensity, color purity and thermal stability, Al3+-doped Ba3Si6O12N2:Eu2+ green phosphors were successfully prepared by a high-temperature sintering method in the current work. The crystal structure was clearly investigated by the XRD patterns and Rietveld refinement. The expanding volume and elemental analysis proved that Si4+ ions can be efficiently substituted by Al3+ ions in the Ba3Si6O12N2:Eu2+ phosphor. With increasing doping of Al3+ ions, the full width at half maximum decreased from 66.88 to 65.12 nm with an optimal color purity of 65.95%, and the reason was clearly elucidated by the Gaussian fitting spectrum and decay times. Moreover, the emission intensity of Ba3Si6O12N2:0.1Eu2+, 0.03Al3+ was 120% of the intensity of the Al-free sample, and the internal quantum efficiency could reach 70%. The thermal stability was also remarkably enhanced as Al3+ substituted Si4+ in Ba3Si6O12N2:0.1Eu2+, and Ba3Si6O12N2:0.1Eu2+, 0.03Al3+ exhibited only 8% emission loss at 200 °C compared with that at ambient temperature. The outstanding thermal stability was clearly explained by the thermoluminescence spectra and configurational coordinate diagram. The results indicate that the introduction of Al3+ ions can be a versatile method to improve the optical properties of silicon oxynitride.