Enhanced orange emission by doping CeB6 in CaAlSiN3:Ce3+ phosphor for application in white LEDs

Abstract

A series of CeB6-doped and CeO2-doped Ca1–xSiAlN3:xCe3+ (denoted as CASN:Ce3+@CeB6 and CASN:Ce3+@CeO2, respectively) were synthesized by alloy-nitridation method under high-purity nitrogen atmosphere. The morphologies, crystal phases, and luminescence properties were investigated in detail. With an increase in the concentration of CeB6, the unit cell volume of CASN:Ce3+@CeB6 slightly increases due to the substitution between ions, which leads to a change of microstructure around Ce3+. CASN:Ce3+@CeB6 efficiently emits yellow-orange light with a maximum emission intensity at around 550 nm for the content x of 0.01 (being in comparable situation, CASN:Ce3+@CeO2 is x = 0.04) when excited at 460 nm. Compared with CASN:Ce3+@CeO2, the red emission component of Ce3+ in CASN:Ce3+@CeB6 is much stronger. This is ascribed to energy transfer of intra-Ce3+ (within one Ce3+ ion) and inter-Ce3+ (between Ce3+ and Ce3+ ions). In addition, the replacements of N3− (0.132 nm for CN = 4) and O2− (0.124 nm for CN = 4) by B2− (0.140 nm for CN = 4), which can lead to a marked expansion of the host lattice and a decrease of the oxidation of samples, are also responsible for the increase of red emission component. Furthermore, CASN:Ce3+@CeB6 phosphor has an excellent thermal stability because of the partial substitution of CeO (CeN) bonds by more covalent CeB. As a result, the outstanding luminescent properties of CASN:Ce3+@CeB6 phosphor make it practical to use in the single phosphor-coated high-color-rendering power white LED.