Synthesis, luminescence properties and nephelauxetic effect of nano stick phosphors K3AlF6:Mn4+ for warm white LED

Abstract

The high uniformity of the phosphors may help to improve their luminescent properties, emission intensities and quantum efficiencies. In order to achieve this goal, a series of nano stick K3AlF6:xMn4+ samples with regular morphology are prepared in this paper. These samples show high photoluminescence quantum yields. Nano stick sample is obtained after recrystallization with vapor diffusion method. Furthermore, color purity, analyses of crystal-field and nephelauxetic effect, the critical distance and the related type of multipolar interaction for the samples were also discussed. The calculation results show that the Mn4+ ions are located at a site of a strong crystal field, and the concentration quenching of Mn4+ in the samples K3AlF6:xMn4+ may be dominated by dipole-quadrupole interactions. Decay lifetime and the photoluminescence QY (quantum yield) of the optimal nano stick sample are 2.50 ms and 89.34%, respectively. The chromaticity coordinates of the optimal nano stick sample are x = 0.6872 and y = 0.3126, which are very close to the NTSC (the national television systems committee) standard values for red color (x = 0.67, y = 0.33). Employing the as-prepared nano stick K3AlF6:xMn4+ as a red component, a high-performance WLEDs with a lower correlated color temperature (CCT = 4170 K) and a high color rendering index (CRI = 85.6) was obtained. It suggests the as-prepared K3AlF6:xMn4+ is a potential commercial red component for warm WLEDs.