Structure, luminescence and energy transfer in Ce3+ and Mn2+ codoped γ-AlON phosphors. Issue 3 (4th January 2019)

• Record Type: Journal Article
• Authors: Si, Jiayong; Wang, Le; Liu, Lihong; Yi, Wei; Cai, Gemei; Takeda, Takashi; Funahashi, Shiro; Hirosaki, Naoto; Xie, Rong-Jun
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 3(2019)
• Page Start: 733
• Page End: 742
• Publication Date: 2019-01-04
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8tc05430d
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Upon UV or blue light excitation, the codoped γ-AlON phosphor has higher luminescence intensity, quantum efficiency and thermal stability than the Mn 2+ -doped γ-AlON due to energy transfer and low total concentration of Ce 3+ and Mn 2+ ions. Abstract : Mn 2+ doped γ-AlON is an interesting narrow-band green emitting phosphor which can be used in wide color gamut white LED backlights for liquid crystal displays (LCDs). However, the spin-forbidden transition of 3d 5 in Mn 2+ results in a quite low absorption efficiency, γ-AlON:Mn 2+ thus has a small external quantum efficiency. Besides Eu 2+, Ce 3+ is another promising sensitizer and is expected to improve the emission of Mn 2+ through a distinctive energy transfer process. In this work, a series of Ce 3+ –Mn 2+ codoped γ-AlON phosphors were synthesized by gas pressure sintering at 1800 °C for 2 h under 0.5 MPa nitrogen gas pressure. The Rietveld refinement analysis shows that Al atoms occupy both 8a and 16d sites, while codoped Ce 3+ and Mn 2+ ions substitute the 8a Al atoms only in the tetrahedral sites. The 27 Al solid state NMR spectrum further confirms the chemical shifts of AlO4 and AlO6 sites at 71.4 and 0 ppm, respectively. The measured PL, CL and decay times have evidenced that a brisk energy transfer occurs between the Ce 3+ and Mn 2+ ions. The energy transfer mechanism from Ce 3+ to Mn 2+ in γ-AlON is a quadrupole–quadrupole interaction and the critical distance is calculated to be 15.97 Å. Upon UV or blue light excitation, the codoped γ-AlON phosphor has higher luminescence intensity, quantum efficiency and thermal stability than the Mn 2+ -doped γ-AlON due to the energy transfer and low total concentration of Ce 3+ and Mn 2+ ions. Meanwhile, the absorption, internal quantum efficiency and external quantum efficiency are raised to 60.2%, 61.3% and 36.9% upon 310 nm excitation.