Site-preferential occupancy induced photoluminescence tuning in (Ca,Ba)5(PO4)3Cl:Eu2+ phosphorsElectronic supplementary information (ESI) available: The selected interatomic distances in Ca4.9(1−x)Ba4.9xEu0.1(PO4)3Cl (x = 0, 0.25, 0.5, 0.75, 1) samples (Table S1); the Rietveld fitting of Ca4.9(1−x)Ba4.9xEu0.1(PO4)3Cl (x = 0, 0.25, 0.75, 1) XRD patterns (Fig. S1); the SEM image of the representative CPOCl, CPOCl-Ba0.5, BPOCl samples (Fig. S2); the normalized Gaussian peaks fitting photoluminescen
Apatite structured (Ca 1− x Ba x ) 5 (PO 4 ) 3 Cl:Eu 2+ (0 ≤ x ≤ 1) solid-solution phosphors were successfully prepared via a typical Pechini sol-gel method. Structural refinement confirms the formation of solid-solution phases under the whole substitution ratio. All samples crystallized in a hexago...
Saved in:
| Main Authors | , , , , , , , |
|---|---|
| Format | Journal Article |
| Published |
03.05.2016
|
| Online Access | Get full text |
Cover
Loading…
| Summary: | Apatite structured (Ca
1−
x
Ba
x
)
5
(PO
4
)
3
Cl:Eu
2+
(0 ≤
x
≤ 1) solid-solution phosphors were successfully prepared
via
a typical Pechini sol-gel method. Structural refinement confirms the formation of solid-solution phases under the whole substitution ratio. All samples crystallized in a hexagonal phase with a space group of
P
6
3
/
m
(176), and there are two kinds of cation sites (4f and 6h) in the host lattice. The as-prepared (Ca
1−
x
Ba
x
)
5
(PO
4
)
3
Cl:Eu
2+
phosphors show similar broad absorptions from 250 nm to 450 nm with peaks around 397 nm. Under 397 nm UV, Ca
5
(PO
4
)
3
Cl:Eu
2+
presents a blue emission centered at 460 nm. By substituting Ba
2+
for Ca
2+
, an unexpected red-shift up to 490 nm was first observed at
x
≤ 0.5 and then a blue-shift after
x
> 0.5 occurred with a resulting emission at 438 nm for
x
= 1. The abnormal red-shift and blue-shift were revealed by the Rietveld structural refinement method and the possible luminescence mechanisms were proposed. The former is attributed to the preferential occupancy of 6h sites by Eu
2+
ions and the expansion of neighboring Ba/Ca-O bond lengths. The latter mainly results from the entering of Eu
2+
ions into the looser Ba
2+
sites. The proposed luminescence mechanism can help reveal the underlying mechanisms in optical adjustment by changing the coordination environment at local sites. In addition, the thermal stability of (Ca,Ba)
5
(PO
4
)
3
Cl:Eu
2+
phosphors were systematically investigated. Generally, the as-prepared (Ca,Ba)
5
(PO
4
)
3
Cl:Eu
2+
phosphors can act as potential emitting-tunable phosphors for potential applications in n-UV based white LEDs.
A schematic presentation of the mechanisms of red-shifted and blue-shifted luminescence in (Ca
1−
x
Ba
x
)
5
(PO
4
)
3
Cl:Eu
2+
(0 ≤
x
≤ 1) solid-solution phosphors. |
|---|---|
| Bibliography: | 0, 0.25, 0.75, 1) with temperatures from 25 °C to 250 °C (Fig. S5). See DOI BPOCl samples (Fig. S4); the normalized PL spectra of Ca BPOCl samples (Fig. S2); the normalized Gaussian peaks fitting photoluminescence emission (PL) spectra of Ca ) Cl 2.45 0, 0.25, 0.5, 0.75, 1) samples at 4f sites and 6h sites (Fig. S3); the high resolution Eu 3d XPS spectra for the representative CPOCl, CPOCl-Ba Eu 0.1 3 4 Electronic supplementary information (ESI) available: The selected interatomic distances in Ca 0.5 x 4.9(1 0, 0.25, 0.75, 1) XRD patterns (Fig. S1); the SEM image of the representative CPOCl, CPOCl-Ba 0, 0.25, 0.5, 0.75, 1) samples (Table S1); the Rietveld fitting of Ca 10.1039/c6ra08053g Ba 4.9 PO |
| ISSN: | 2046-2069 |
| DOI: | 10.1039/c6ra08053g |