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Abstract
To modify the luminescence properties of Ce3+-doped Y3Al5O12 (YAG) phosphors, they have been coated with a carbon layer by chemical vapor deposition and subsequently heat-treated at high temperature under N2 atmosphere. Luminescence of the carbon coated YAG:Ce3+ phosphors has been investigated as a function of heat-treatment at 1500 and 1650 °C. The 540 nm emission intensity of C@YAG:Ce3+ is the highest when heated at 1650 °C, while a blue emission at 400–420 nm is observed when heated at 1500 °C but not at 1650 °C. It is verified by X-ray diffraction (XRD) that the intriguing luminescence changes are induced by the formation of new phases in C@YAG:Ce3+-1500 °C, which disappear in C@YAG:Ce3+-1650 °C. In order to understand the mechanisms responsible for the enhancement of YAG:Ce3+ emission and the presence of the blue emission observed for C@YAG:Ce3+-1500 °C, the samples have been investigated by a combination of several electron microscopy techniques, such as HRTEM, SEM-CL, and SEM-EDS. This local and cross-sectional analysis clearly reveals a gradual transformation of phase and morphology in heated C@YAG:Ce3+ phosphors, which is related to a reaction between C and YAG:Ce3+ in N2 atmosphere. Through reaction between the carbon layer and YAG host materials, the emission colour of the phosphors can be modified from yellow, white, and then back to yellow under UV excitation as a function of heat-treatment in N2 atmosphere.
Highlights
Yttrium aluminum garnet Y3 Al5 O12 (YAG) is widely used as an optical host material due to its remarkable chemical stability, good mechanical properties, and flexible structural compatibility [1,2,3].Many rare-earth or transition ions (Ce3+, Tb3+, Yb3+, Eu3+, Tm3+, Ho3+, Cr3+, etc.) doped YAG materials have been reported, and applied in the illumination and display field [4,5,6,7,8]
No X-ray diffraction (XRD) peaks for crystalline carbon are detected in coated YAG:Ce3+ (C@YAG):Ce3+ samples, suggesting that the carbon film deposited on the surface of YAG:Ce3+ is amorphous or very thin
Some additional peaks due to secondary phases are detected for C@YAG:Ce3+ -1500 ◦ C
Summary
Yttrium aluminum garnet Y3 Al5 O12 (YAG) is widely used as an optical host material due to its remarkable chemical stability, good mechanical properties, and flexible structural compatibility [1,2,3].Many rare-earth or transition ions (Ce3+ , Tb3+ , Yb3+ , Eu3+ , Tm3+ , Ho3+ , Cr3+ , etc.) doped YAG materials have been reported, and applied in the illumination and display field [4,5,6,7,8]. Yttrium aluminum garnet Y3 Al5 O12 (YAG) is widely used as an optical host material due to its remarkable chemical stability, good mechanical properties, and flexible structural compatibility [1,2,3]. It has been demonstrated that carbon coating deposited on the surface of BaMgAl10 O17 :Eu2+ phosphors is an effective way to improve the intensity and thermal stability of oxide phosphors [22]. The carbon coated phosphors show a higher emission intensity and a better oxidation resistance at high temperature than uncoated phosphors. These results motivate us to perform carbon deposition on the surface of YAG:Ce3+ and investigate the effect of post heat-treatment on the structure and luminescence properties of YAG:Ce3+
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