Tunable Red Luminescence of Mn[sup 2+]-Doped NaCaPO[sub 4] Phosphors

Abstract

Mn 2+ -doped NaCaPO 4 were synthesized by a solid-state reaction. The structure and luminescence were investigated. The main excitation bands located at a band extending from 380 to 450 nm could match the emission of UV light emitting diode chips. The phosphors exhibited the emission in the wavelength range of 600-750 nm. The luminescence showed a redshift with the increase in Mn 2+ doping concentrations. This color points could be tunable by controlling the doping of Mn 2+ in NaCaPO 4 . The thermal stability of the luminescence of Mn 2+ ions was evaluated at different temperatures. The doping mechanism of Mn 2+ ions was discussed.The luminescence of Mn 2+ -ion-doped inorganic compounds usually gives a broad-band emission, which depends on the host lattice. From the Tanabe-Sugano diagram, the emission corresponds to the 4 T 1 → 6 A 1 transition in Mn 2+ ions and can vary in a wide range in all the spectral wavelengths. 1 For example, the tetrahedrally coordinated Mn 2+ usually gives a green emission, whereas the octahedrally coordinated Mn 2+ gives an orange to red emission. 2 This gives a wide usage of Mn 2+ -doped compounds for fluorescent lamps, cathode ray tubes, and potential applications in white light emitting diodes ͑LEDs͒. 3 In recent years, there has been an increased interest in the investigations of luminescent materials with the structures derived from the ABPO 4 family ͑A and B are mono-and divalent cations, respectively͒. For example, Eu 2+ -doped LiSrPO 4 was investigated to have a higher emission intensity compared with the blue-emitting phosphor BaMgAl 10 O 17 :Eu 2+ . 4 NaCaPO 4 :Eu 2+ was a potential greenemitting phosphor for white LEDs. 5 Eu 2+ -doped KSrPO 4 showed a higher thermally stable luminescence, which was better than commercially available Y 3 Al 5 O1 2 :Ce 3+ at a temperature higher than 225°C. 6 Chan et al. reported that Mn 2+ -doped LiZnPO 4 has potential applications as a green-yellow-emitting phosphor in LEDs. 7 In this work, NaCa 1−x Mn x PO 4 ͑x = 0.01, 0.05, 0.08, 0.12, 0.16, 0.20, 0.22͒ were prepared by solid-state reaction and were characterized by excitation and emission spectroscopes. The luminescence properties, e.g., the wavelength position, emission intensity, full wavelength at half-maximum ͑FWHM͒, and color coordinates, were discussed depending on the Mn 2+ doping levels. The thermal stability of the luminescence of Mn 2+ ions was evaluated at different temperatures. ExperimentalNaCa 1−x Mn x PO 4 ͑x = 0.01, 0.05, 0.08, 0.12, 0.16, 0.20, 0.22͒ phosphors were synthesized by solid-state reaction. The starting material was a stoichiometric mixture of reagent grade Na 2 CO 3 , CaCO 3 , NH 4 H 2 PO 4 , and MnCO 3 . First, the mixture was heated up to 350°C and kept at this temperature for 10 h. The obtained powder was thoroughly mixed and then heated up to 750°C and was kept at this temperature for 8 h. After that, the sample was mixed and heated at 900°C for 10 h in crucibles along with the reducing agent ͑active carbon͒.X-ray diffraction ͑XRD͒ data were collected on...

Photoluminescence properties of (Ce3+, Mn2+)-codoped CaCO3 red phosphor

“…5, the peak wavelength of the red emission band progressively red-shifted with increasing N from $620 nm (N ¼ 0.005) to $640 nm (N ¼ 0.04). Similar red shift in the peak wavelength with increasing Mn 2þ concentration has been observed in single Mn 2þ -doped phosphors such as MgO-Al 2 O 3 -Ga 2 O 3 :Mn 2þ , 11 ZnSiO 4 :Mn 2þ , 12 and NaCaPO 4 :Mn 2þ , 13 as well as in codoped phosphors such as (Sr,Ca) 2 P 2 O 7 :Eu 2þ , Mn 2þ , 14 17 and MgY 4 Si 3 O 13 :Ce 3þ , Mn 2þ . 18 As the ionic radius of Mn 2þ ion is shorter than that of the replaced cation atom in the host crystal, the crystal lattice of the phosphor shrinks, especially after high Mn 2þ ion doping.…”

“…9, a distinct blue shift with T in the Mn 2þ red emission band was observed. Similar blue shifts in the Mn 2þ -related emission bands were observed in NaCaPO 4 , 13 50) although no attempts to provide a quantitative description of these shifts have been made until now. Here, we consider thermal excitation of the 4 T 1 -state electrons.…”

Fluorescence emission spectrum and energy transfer in Eu and Mn co-doped Ba2Ca(BO3)2 phosphors

“…Compared with this result, we suggest that the emission band at 514 nm comes from Eu 2 + ions at Ba 2 + sites. T 2 ( 4 G) and 4 T 1 ( 4 G) levels, respectively [14]. The excitation spectrum is very similar to those exhibited by Mn 2 + ions in octahedral coordination compounds, such as KMgCl 3 and KCaCl 3 [15].…”

Interaction between the exchanged Mn2+ and Yb3+ ions confined in zeolite-Y and their luminescence behaviours

“…Thus, TM and Ln ions codoped zeolite may serve as a good candidate for comparative study of their photoluminescence (PL), owing to the distinct photo-stimuli responses of TM and Ln ions to surrounding chemical enviorenments. Detailedly, Mn 2+ ion is a well-studied luminescent center and commercially applicable in lighting and display2223. The emission color of Mn 2+ can be tuned from green to deep red2425, depending on its coordinated chemical environment.…”