Synthesis and optical characterization of Tm3+ doped CaAl4O7 for near-UV LED-based white light
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- 作者：A. Suresh Kumara ; b ; R. Arun Kumara ; b ; rarunpsgtech@yahoo.com ; rak@phy.psgtech.ac.in ; Rama Ranjan Bhattacharjeec
- 关键词：CaAl4O7 ; Oxide materials ; Luminescence ; Pechini method
- 刊名：Journal of Luminescence
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：182
- 期：Complete
- 页码：130-136
- 全文大小：1640 K
- 卷排序：182
文摘
A blue light emitting phosphor Ca1−xAl4O7:Tmx3+ was synthesized by the conventional Pechini sol–gel method. Synthesized polymeric resin was calcined at 800, 850, 900, 950 and 1000 °C for 2 h. The samples were analyzed with powder XRD, TG-DSC, UV–vis-NIR (diffuse reflectance spectra – DRS) and spectrofluorophotometer. Thermal degradation of the derived gel was observed up to 400 °C and the desired phase formation initiates from 800 °C. XRD pattern confirms the monoclinic phase of CaAl4O7:Tm3+ phosphors with a=12.860 Å, b=8.865 Å, c=5.396 Å, and β=107.06°. Diffuse reflectance and photoluminescence excitation spectral studies reveal the corresponding absorption and emission properties of trivalent state of thulium ion. The major emission peak at 460 nm corresponding to 1D2→→3F4 of Tm3+ ions was observed. The decrease in emission intensity and luminescence life-times with increase of activator concentration was observed and it is mainly due to the phonon – assisted cross – relaxation processes between Tm3+ ions. The energy transfer mechanism between the nearby Tm3+ ions was analysed by fitting the non-exponential fitting curve by IH model and the results were discussed. The critical distance for the energy transfer of the phosphor is calculated to be 6 Å. Emission in the blue region is expected and the same can be evidenced in the CIE chromaticity diagram with high color purity (73%). Concentration quenching occurs with Tm3+ at 5 mol%. The obtained CaAl4O7:Tm3+ phosphors have potential applications in the area of near UV based white light emitting diodes.