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For the first time, a new langbeinite-type phosphate, namely potassium terbium tantalum tris(phosphate), K2Tb1.5Ta0.5(PO4)3, has been prepared successfully using a high-temperature flux method and has been structurally characterized by single-crystal X-ray diffraction. The results show that its structure can be described as a three-dimensional open framework of [Tb1.5Ta0.5(PO4)3]∞ interconnected by K+ ions. The TbIII and TaV cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu3+-activated photoluminescence spectroscopic properties were studied. A series of Eu3+-doped phosphors, i.e. K2Tb1.5–xTa0.5(PO4)3:xEu3+ (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid-state reaction and the photoluminescence properties were studied. The results show that under near-UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu3+ concentration from 0 to 0.1, because of the efficient Tb3+→Eu3+ energy-transfer mechanism.
Supporting information
CCDC reference: 1875420
Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXL2014 (Sheldrick, 2015); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Potassium terbium tantalum tris(phosphate)
top
Crystal data top
K2Tb1.5Ta0.5(PO4)3 | Mo Kα radiation, λ = 0.71073 Å |
Mr = 691.96 | Cell parameters from 905 reflections |
Cubic, P213 | θ = 2.8–24.5° |
a = 10.3262 (6) Å | µ = 15.77 mm−1 |
V = 1101.09 (19) Å3 | T = 296 K |
Z = 4 | Block, colourless |
F(000) = 1252 | 0.18 × 0.17 × 0.15 mm |
Dx = 4.174 Mg m−3 | |
Data collection top
Bruker SMART APEXII CCD area detector diffractometer | 927 independent reflections |
Radiation source: fine-focus sealed tube | 907 reflections with I > 2σ(I) |
Detector resolution: 83.33 pixels mm-1 | Rint = 0.045 |
ω scans | θmax = 28.2°, θmin = 2.8° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996; Bruker, 2016) | h = −9→13 |
Tmin = 0.108, Tmax = 0.453 | k = −13→13 |
7448 measured reflections | l = −13→10 |
Refinement top
Refinement on F2 | w = 1/[σ2(Fo2) + 4.889P] where P = (Fo2 + 2Fc2)/3 |
Least-squares matrix: full | (Δ/σ)max = 0.006 |
R[F2 > 2σ(F2)] = 0.023 | Δρmax = 0.56 e Å−3 |
wR(F2) = 0.043 | Δρmin = −0.77 e Å−3 |
S = 1.13 | Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
927 reflections | Extinction coefficient: 0.0030 (2) |
61 parameters | Absolute structure: Flack x determined using 368 quotients [(I+)-(I-)]/[(I+)+(I-)]
(Parsons et al., 2013) |
1 restraint | Absolute structure parameter: 0.027 (13) |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
K1 | 0.5701 (2) | 0.5701 (2) | 0.5701 (2) | 0.0351 (8) | |
K2 | 0.2043 (3) | 0.2957 (3) | 0.7043 (3) | 0.0427 (11) | |
Tb1 | 0.58140 (4) | 0.41860 (4) | 0.91860 (4) | 0.01756 (19) | 0.806 (4) |
Ta1 | 0.58140 (4) | 0.41860 (4) | 0.91860 (4) | 0.01756 (19) | 0.194 (4) |
Tb2 | 0.15006 (4) | 0.65006 (4) | 0.84994 (4) | 0.0194 (2) | 0.694 (4) |
Ta2 | 0.15006 (4) | 0.65006 (4) | 0.84994 (4) | 0.0194 (2) | 0.306 (4) |
P1 | 0.4653 (2) | 0.7390 (2) | 0.8772 (2) | 0.0208 (5) | |
O1 | 0.3272 (9) | 0.7348 (9) | 0.9196 (9) | 0.061 (3) | |
O2 | 0.5147 (9) | 0.6081 (8) | 0.8461 (9) | 0.058 (3) | |
O3 | 0.5473 (13) | 0.7969 (11) | 0.9841 (11) | 0.082 (4) | |
O4 | 0.4798 (11) | 0.8269 (11) | 0.7635 (10) | 0.072 (3) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
K1 | 0.0351 (8) | 0.0351 (8) | 0.0351 (8) | −0.0008 (10) | −0.0008 (10) | −0.0008 (10) |
K2 | 0.0427 (11) | 0.0427 (11) | 0.0427 (11) | 0.0013 (11) | −0.0013 (11) | 0.0013 (11) |
Tb1 | 0.01756 (19) | 0.01756 (19) | 0.01756 (19) | 0.00050 (16) | 0.00050 (16) | −0.00050 (16) |
Ta1 | 0.01756 (19) | 0.01756 (19) | 0.01756 (19) | 0.00050 (16) | 0.00050 (16) | −0.00050 (16) |
Tb2 | 0.0194 (2) | 0.0194 (2) | 0.0194 (2) | 0.00122 (17) | −0.00122 (17) | −0.00122 (17) |
Ta2 | 0.0194 (2) | 0.0194 (2) | 0.0194 (2) | 0.00122 (17) | −0.00122 (17) | −0.00122 (17) |
P1 | 0.0252 (12) | 0.0189 (11) | 0.0181 (11) | 0.0005 (9) | −0.0080 (9) | 0.0038 (9) |
O1 | 0.049 (6) | 0.079 (7) | 0.057 (5) | 0.013 (5) | 0.025 (5) | −0.008 (5) |
O2 | 0.074 (6) | 0.043 (5) | 0.056 (5) | 0.026 (4) | −0.005 (5) | −0.016 (5) |
O3 | 0.113 (10) | 0.077 (8) | 0.058 (6) | 0.017 (7) | −0.051 (6) | −0.024 (6) |
O4 | 0.092 (8) | 0.065 (6) | 0.060 (6) | −0.023 (6) | −0.024 (6) | 0.048 (5) |
Geometric parameters (Å, º) top
K1—O2 | 2.933 (10) | K2—O4ix | 3.295 (12) |
K1—O2i | 2.933 (10) | Tb1—O4iii | 2.198 (9) |
K1—O2ii | 2.933 (10) | Tb1—O4ii | 2.198 (9) |
K1—O4iii | 3.086 (13) | Tb1—O4x | 2.198 (9) |
K1—O4iv | 3.086 (13) | Tb1—O2xi | 2.205 (8) |
K1—O4v | 3.086 (13) | Tb1—O2ix | 2.205 (8) |
K1—O3iii | 3.121 (12) | Tb1—O2 | 2.205 (8) |
K1—O3iv | 3.121 (12) | Tb2—O3vii | 2.089 (9) |
K1—O3v | 3.121 (12) | Tb2—O3xii | 2.089 (9) |
K2—O1vi | 2.974 (10) | Tb2—O3ix | 2.089 (9) |
K2—O1iv | 2.974 (10) | Tb2—O1iv | 2.152 (10) |
K2—O1vii | 2.974 (10) | Tb2—O1xiii | 2.152 (10) |
K2—O3viii | 3.219 (15) | Tb2—O1 | 2.152 (10) |
K2—O3ix | 3.219 (15) | P1—O2 | 1.481 (8) |
K2—O3iii | 3.219 (15) | P1—O4 | 1.491 (8) |
K2—O4iii | 3.295 (12) | P1—O1 | 1.492 (9) |
K2—O4viii | 3.295 (12) | P1—O3 | 1.514 (10) |
| | | |
O4iii—Tb1—O4ii | 90.1 (4) | O3vii—Tb2—O1iv | 86.6 (4) |
O4iii—Tb1—O4x | 90.1 (4) | O3xii—Tb2—O1iv | 172.7 (4) |
O4ii—Tb1—O4x | 90.1 (4) | O3ix—Tb2—O1iv | 92.9 (4) |
O4iii—Tb1—O2xi | 172.4 (4) | O3vii—Tb2—O1xiii | 92.9 (4) |
O4ii—Tb1—O2xi | 90.1 (4) | O3xii—Tb2—O1xiii | 86.6 (4) |
O4x—Tb1—O2xi | 82.3 (4) | O3ix—Tb2—O1xiii | 172.7 (4) |
O4iii—Tb1—O2ix | 82.3 (4) | O1iv—Tb2—O1xiii | 94.3 (3) |
O4ii—Tb1—O2ix | 172.4 (4) | O3vii—Tb2—O1 | 172.7 (4) |
O4x—Tb1—O2ix | 90.1 (4) | O3xii—Tb2—O1 | 92.9 (4) |
O2xi—Tb1—O2ix | 97.5 (3) | O3ix—Tb2—O1 | 86.6 (4) |
O4iii—Tb1—O2 | 90.1 (4) | O1iv—Tb2—O1 | 94.3 (3) |
O4ii—Tb1—O2 | 82.3 (4) | O1xiii—Tb2—O1 | 94.3 (3) |
O4x—Tb1—O2 | 172.4 (4) | O2—P1—O4 | 110.5 (6) |
O2xi—Tb1—O2 | 97.5 (3) | O2—P1—O1 | 111.5 (6) |
O2ix—Tb1—O2 | 97.5 (3) | O4—P1—O1 | 110.2 (6) |
O3vii—Tb2—O3xii | 86.1 (5) | O2—P1—O3 | 109.0 (6) |
O3vii—Tb2—O3ix | 86.1 (5) | O4—P1—O3 | 106.1 (6) |
O3xii—Tb2—O3ix | 86.1 (5) | O1—P1—O3 | 109.4 (7) |
Symmetry codes: (i) y, z, x; (ii) z, x, y; (iii) −x+1, y−1/2, −z+3/2; (iv) y−1/2, −z+3/2, −x+1; (v) −z+3/2, −x+1, y−1/2; (vi) −x+1/2, −y+1, z−1/2; (vii) z−1, x, y; (viii) −z+1, x−1/2, −y+3/2; (ix) −y+1, z−1/2, −x+3/2; (x) −y+3/2, −z+1, x+1/2; (xi) −z+3/2, −x+1, y+1/2; (xii) x−1/2, −y+3/2, −z+2; (xiii) −z+1, x+1/2, −y+3/2. |
The luminescent lifetime of the 5D4→7F5
transition of the
Tb3+ ion (excited: 378 nm; emission: 551 nm) for phosphors
K2Tb1.5-xTa0.5(PO4)3:xEu3+
(x = 0~ 0.10) topSample number | Eu3+ concentration | Tb3+ emission lifetime (ms) | Energy transfer efficiency (%) |
1 | x = 0 | 16.5 | 0 |
2 | x = 0.01 | 5.7 | 65.5 |
3 | x = 0.03 | 3.4 | 79.4 |
4 | x = 0.05 | 2.2 | 86.7 |
5 | x = 0.07 | 1.8 | 89.1 |
6 | x = 0.10 | 1.3 | 92.1 |
The CIE coordinates of phosphors
K2Tb1.5-xTa0.5(PO4)3:xEu3+
(x = 0~ 0.10) topK2Tb1.5-xEuxTa0.5(PO4)3 | CIE x | CIE y |
1# x = 0.00 | 0.2988 | 0.6208 |
2# x = 0.01 | 0.4764 | 0.4836 |
3# x = 0.03 | 0.5475 | 0.4297 |
4# x = 0.05 | 0.5591 | 0.4087 |
5# x = 0.07 | 0.5901 | 0.3973 |
6# x = 0.10 | 0.6034 | 0.3868 |
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