Abstract
Synthesizing phosphors with high performance is still a necessary work for phosphor-converted white light-emitting diodes (W-LEDs). In this paper, three series of CaAlSiN3:Eu2+ (denoted as CASN:Eu2+) phosphors using Eu2O3, EuN and EuB6 as raw materials respectively are fabricated by under the alloy precursor normal pressure nitridation synthesis condition. We demonstrate that CASN:Eu2+ using nano-EuB6 as raw material shows higher emission intensity than others, which is ascribed to the increment of Eu2+ ionic content entering into the crystal lattice. An improved thermal stability can also be obtained by using nano-EuB6 due to the structurally stable status, which is assigned to the partial substitution of Eu–O (Eu–N) bonds by more covalent Eu–B ones that leads to a higher structural rigidity. In addition, the W-LEDs lamp was fabricated to explore its possible application in W-LEDs based on blue LEDs. Our results indicate that using EuB6 as raw materials can provide an effective way of enhancing the red emission and improving the thermal stability of the CASN:Eu2+ red phosphor.
Highlights
White light-emitting diodes (W-LEDs) are considered as the next-generation solid-state lighting system due to the high luminous efficiency, long operation time, reliability environmental friendliness [1,2,3]
It should be mentioned that the powders synthesized by EuN as the raw material are easier to be oxidized due to its high activity
The small amount of oxygen impurities in CASN:Eu2+ @EuB6 are attributed to the CaSi alloy, which could be reduced under a reducing atmosphere
Summary
White light-emitting diodes (W-LEDs) are considered as the next-generation solid-state lighting system due to the high luminous efficiency, long operation time, reliability environmental friendliness [1,2,3]. The alloy precursor normal pressure nitridation process is easier to operate rested upon high active alloy without high temperature (≥1800◦ ) and high pressure (≥1 MPa) requirement, whereas the oxidation of the raw material is difficult to avoid. Higher oxygen content in raw materials necessitates it to be processed with oxidation-reduction treatment To this end, several very simple methods like gas reduction nitridation (GRN) method [25,26] and carbothermal reduction and nitridation (CTRN) method [27,28] are applied to the preparation of CASN:Eu2+. Alloy precursor and non-oxygen raw materials will help improve luminescence performance of CASN:Eu2+ series nitride phosphors. A high performance CASN:Eu2+ red phosphors, using nano-EuB6 as raw materials, were obtained by alloy precursor normal pressure nitridation. The possible performance of the red phosphor in W-LED was investigated
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