Structure and Luminescence Properties of Mn4+-Activated K3TaO2F4

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Structure and Luminescence Properties of Mn4+-Activated K3TaO2F4 Red Phosphor for White LEDs Yang Zhou, Shuai Zhang, Xiaoming Wang,* and Huan Jiao* Key Laboratory of Macromolecular Science of Shaanxi Province, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Laboratory for Advanced Energy Technology, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 Shaanxi Province, P. R. China

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S Supporting Information *

ABSTRACT: A novel red oxyfluoride phosphor K3TaO2F4:Mn4+ has been prepared by a simple two-step synthesis method. The structure, composition, and luminescence properties of K3TaO2F4:Mn4+ phosphors were investigated and discussed in detail. The real structure of K3TaO2F4 was carefully studied through X-ray powder diffraction data Rietveld refinement. K3TaO2F4 holds a D4h group symmetry [TaO2F4]3− octahedron with the oxygen occupying the para-position. Under ultraviolet (UV) and blue light excitation, K3TaO2F4:Mn4+ phosphor emits a narrow band red emission peaking at 630 nm. Highperformance warm white-light-emitting diodes (WLEDs) were fabricated using a blue LED chip, YAG:Ce3+ yellow phosphor, and K3TaO2F4:Mn4+ red phosphor. This device exhibits high color quality (CCT = 3488 K, Ra = 93.0, R9 = 90.0), which indicates that Mn4+-doped K3TaO2F4 would be a promising red phosphor for WLED applications.

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INTRODUCTION Over the past decade, white light-emitting diodes (WLEDs) have attracted much attention because of their superior properties and important applications in solid-state lighting.1,2 Currently, the most widely used method to produce white light is to combine InGaN blue-emitting LED chip and yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+).3,4 However, this yellow and blue combination lacks a red light component and leads to a cool white light performance with a low color rendering index (CRI, Ra < 80) and a high correlated color temperature (CCT > 4500 K). This limitation restricts the application of LEDs on many devices such as liquid crystal displays (LCD), special surgery lighting, and other devices that need a high color rendering capability. To resolve this problem and obtain a warm white light output, it is necessary to compensate the red phosphors in the WLED devices rather than a single yellow phosphor. Consequently, Eu2+-doped nitride phosphors are employed as red components for the fabrication of warm WLEDs. This addition greatly improves the performance of WLED devices with a high CRI value of 80 and a low CCT value of 2700−4000 K.5−9 However, the synthesis of nitride phosphors usually requires high temperature and extra N2 © XXXX American Chemical Society

pressure which increases production cost. Therefore, exploring highly efficient, stable, and low-cost red phosphors is a hot topic for current warm WLED research. Currently, the transition metal ion Mn4+-activated red phosphors have attracted much interest due to their good thermal stability, low cost, and high luminous efficacy.10−14 There are two categories of Mn4+-activated phosphor hosts. One is oxide, and the other is (oxy)fluoride. Mn4+-doped oxide phosphors, such as Mg2TiO4:Mn4+,15 CaAl12O19:Mn4+,16 CaMg2Al16O27:Mn4+,17 and Sr4Al14O25:Mn4+,18 show promising red emission in WLEDs, but most of these emission bands extend to the near-infrared region, which are located outside the sensitivity range of human eyes (λ ≥ 700 nm). However, Mn4+-activated (oxy)fluoride phosphors exhibit the strongest narrow emission spectrum at ∼630 nm under ultraviolet (UV) or blue light excitation, which makes Mn4+-doped (oxy)fluoride phosphors very suitable as red components for fabrication of warm WLEDs and display applications.19−21 A series of Mn4+-activated red (oxy)fluoride phosphors have Received: December 22, 2018

A

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 1. Synthesis schematic diagram of K3TaO2F4 and K3TaO2F4:Mn4+.

been reported, such as A2XF6:Mn4+ (A = Na+, K+, Rb+, Cs+; X = Si4+, Ti4+, Ga3+, Ge4+, Zr4+, Sn4+, Hf4+),22−25 cryolite A2BXF6:Mn4+ (B = Li+, Na+, K+; X = Al3+, Ga3+),26−29 A2NbOF5:Mn 4+ (A = Cs+ , Rb+ ; A2 = Ba),30−32 and A2WO2F4:Mn4+ (A = Na+, Cs+)33,34 These phosphors exhibit a promising narrow emission under blue light excitation and will be good red phosphor candidates for WLED application. The oxyfluoride compound K3TaO2F4 was first reported as a tetragonal phase without detailed crystal structure by J. P. Chaminade in 1974.35 However, the powder diffraction pattern of K3TaO2F4 is the same as that of K3TaOF6. Accordingly, for a long time it was believed that K3TaO2F4 has cubic symmetry with a space group Fm3̅m (No. 225). This was until the report from Boča et al. in 2011 which suggested that previously reported cubic phase oxyfluoride K3TaOF6 is actually K3TaO2F4, and tetragonal phase K3TaO2F4 should be K3[TaO4]·K3[TaF4O2].36 The structure of the latter compound K3[TaO4]·K3[TaF4O2] was solved by single crystal data, but the real structure of the former cubic phase K3TaO2F4 is still unknown. In this paper, the real structure of K3TaO2F4 was analyzed by Rietveld refinement of X-ray powder diffraction data, and the luminescence properties of red phosphor K3TaO2F4:Mn4+ were also investigated and discussed in detail. The K3TaO2F4:Mn4+ shows a high-color-purity red emission under blue light excitation, which may have the potential to improve the CCT and CRI levels of WLEDs.

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minutes, the mixed sample was transferred to a 25 mL Teflon-lined autoclave with a small amount HF. The autoclave was maintained at 120 °C for 30 min. In the end, a series of K3TaO2F4:Mn4+ phosphors were obtained after drying at 80 °C for 12 h. The color of K3TaO2F4:Mn4+ phosphor is pink in room light and red under UV light. For the further optimization of luminescence properties, different concentrations of Mn4+-doped K3TaO2F4 samples were synthesized, and the actual doping concentration has been measured, as shown in Table 1.

Table 1. Atomic Absorption Spectrophotometer (AAS) Results for K3TaO2F4:Mn4+ Phosphors Prepared with Different Amounts of K2MnF6 molar ratio of Ta to Mn

dopant amount of Mn4+ (mol %) in K3TaO2F4

S1 S2 S3 S4 S5 S6

100:6.0 100:7.0 100:7.5 100:8.0 100:9.0 100:10.0

5.73 6.69 6.92 7.45 7.70 8.06

Characterization. The XRD patterns of the as-synthesized samples were analyzed by X-ray diffraction (XRD, Rigaku MiniFlex 600) with graphite monochromatized Cu Kα radiation (λ = 0.154 18 nm) and scanning range from 10° to 80°. The actual doping concentration was measured on an atomic absorption spectroscopy instrument (AAS, Hitachi, ZA3000). Rietveld refinements on X-ray diffraction data were performed using the software Topas 5, and the bond-valence sum (BVS) calculation was performed using the program Bond St in fullprof software.37 The morphologies of the synthesized samples were investigated by using a Philips-FEI Quanta 25 scanning electron microscopy (SEM) instrument with an energydispersive X-ray spectrometer (EDS, INCA-Oxford, High Wycombe, UK). The photoluminescence (PL) and photoluminescence excitation (PLE) spectra were obtained using a fluorescence spectrophotometer equipped with a 450 W Xe lamp source (Hitachi, F-4600). The decay curves of the synthesized samples were analyzed by fluorescence spectrophotometer with a 150 W microsecond pulsed lamp as the excitation source (Edinburgh, FLS 920). The temperature-dependent emission spectra were acquired on a Hitachi F-4600 fluorescence spectrophotometer with a thermal quenching analyzed system (TAP-02). The quantum efficiencies were obtained on an absolute PL quantum yield spectrometer (Hamamatsu, C9920-02G). Fabrication of WLEDs. WLED devices were fabricated using blue InGaN chips with amounts of commercial yellow phosphor YAG:Ce3+

EXPERIMENTAL SECTION

Materials and Synthesis. Raw materials Ta2O5 (99.99%), KHF2 (99.99%), KMnO4 (99.99%), H2O2 (30%), and HF (49%) were purchased from Aladdin Industrial Inc. (Shanghai, China). All chemicals were used as obtained from the manufacturer without any purification As shown in Figure 1, stoichiometric amounts of Ta2O5 and KHF2 were mixed together in an agate mortar and pestle, isostatically pressed, and sintered in N2−H2 atmosphere at 360 °C for 120 min. The following reaction was observed:

Ta 2O5 + KHF2 → K3TaO2 F4 + HF↑

sample

(1)

The K3TaO2F4 sample was obtained after cooling to room temperature naturally. Samples of K3Ta1−xO2F4:xMn4+ (x = 0.060, 0.070, 0.075, 0.080, 0.090, 0.100) were prepared by hydrothermal method. Prepared K3TaO2F4 was weighted and mixed with different amounts of K2MnF6 in an agate mortar. After grinding for some B

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry and obtained K3TaO2F4:Mn4+ red phosphor. The as-fabricated WLED devices obtained warm white lights under driven current from 20 to 350 mA, whose luminescence properties were measured at the same time by using an integrating sphere spectroradiometer system (HAAS-1200, Everfine).

Table 4. Some Bond Lengths and Bond Angles of K3TaO2F4

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RESULTS AND DISCUSSION Phase Identification, Morphology, and Composition Analysis. The K3TaO2F4 compound was first reported as a tetragonal phase without detailed crystal structure by J.P. Chaminade in 1974.35 However, the powder diffraction pattern of K3TaO2F4 is the same as that of K3TaOF6 which is a cubic structure with a space group Fm3̅m (No. 225). Recently, Boča et al. suggested that these two oxyfluorides are actually the same compound.38 Because the single crystals of K3TaO2F4 and K3TaOF6 are not easy to synthesize, complete structural determinations are mainly based on X-ray powder data. To confirm the real structure of K3TaO2F4, we carefully studied the composition of K3TaO2F4 and analyzed its structure through X-ray powder diffraction data Rietveld refinements. Because the X-ray powder diffraction pattern of K3TaO2F4 is the same as that of K3TaOF6, we use the cubic structure of K3TaOF6 as the initial structural model. After trying several subgroups of K3TaOF6 Fm3̅m (No. 225), we found that tetragonal space group I4/mmm (No. 139) can perfectly match the structure Rietveld refinements. The lattice parameters are a = 6.3057(4) Å, c = 8.9173(6) Å, V = 354.57(5) Å3, and Z = 2. The refinement result based on XRD data is summarized in Table 2, and the atomic positions of the structure are listed in

K3TaO2F4 tetragonal I4/mmm (No. 139) 6.3057(4) 8.9173(6) 354.57(5) 2 Rietveld refinement/Topas Cu Kα (λ = 1.54178 Å) 293 10 ≤ 2θ ≤ 80 3501 PV_TCHZ 4.73 6.48 5.06 1.28

Table 3. Table 4 lists some of the bond lengths and bond angles based on the crystallographic data. The refined Ta−F Table 3. Crystallographic Data of K3TaO2F4 site

Wyck

x

y

z

s.o.f.

Beq/Å2

K1 K2 Ta F O

4 2 2 8 4

0.0000 0.0000 0.0000 0.7794(0) 0.0000

0.5000 0.0000 0.0000 0.7794(0) 0.0000

0.2500 0.5000 0.0000 0.0000 0.7941(0)

1 1 1 1 1

2.448 1.816 0.624 3.869 3.948

length/Å

bond angle

angle/deg

K−F K−O Ta−F Ta−O

2.48(8)−3.16(3) 2.61(8)−3.17(6) 1.97(1) 1.84(1)

F−K−F O−K−F O−Ta−F F−Ta−F

52.27(5)−170.62(1) 50.34(3)−119.90(0) 90.00 90.00−180.00

and Ta−O distances are 1.97(1) and 1.84(1) Å, respectively. According to Pauling’s second crystal rule, the BVS for each site indicates the charge on an anion or a cation.39 BVS calculations of Ta5+, O2−, and F− are shown in Table S1. The Ta, F, and O bond valences are 5.564, 1.202, and 1.730, respectively.40 The observed and calculated XRD patterns of K3TaO2F4 as well as the difference profile are illustrated in Figure 2 with residual factors of Rwp = 6.48%, Rp = 4.73%, and GOF = 1.28. The schematic crystal structure of K3TaO2F4 is shown in Figure 3. The Ta5+ ions are located at the center of the [TaO2F4]3− octahedron, which are attached to K+ ions through ionic bonding. Mn4+ ions would occupy the site of Ta5+ in the center of octahedron because of the similar ionic size (rMn4+ = 0.53 Å, rTa5+ = 0.69 Å, CN = 6). The charge balance is mainly compensated by substitution of O2− by F−. The local coordination environment surrounding of Mn4+ become [MnOF5]3−, instead of the original [TaO2F4]3−. Unlike the oxygen occupying ortho-positions in the [WO2F4]2− octahedron of Na2WO2F4, the octahedron [TaO2F4]3− in K3TaO2F4 holds a D4h group symmetry with the oxygen occupying the para-position. During the process of Rietveld refinement, we use common mixture occupancies of O and F in the two anion sites. However, the O and F in two anion sites will be automatically separated during the refinement; O fully occupies the 4a site, and F fully occupies 8b site. This structure feature will also affect the subsequent luminescence properties especially the intensity of zero phonon line (ZPL). The morphologies of the K3TaO2F4 precursor prepared at 360 °C and the final product K3TaO2F4:Mn4+ dried at 80 °C are shown in Figure 4. The SEM image in Figure 4a shows that the sample exhibited heavy agglomeration. The synthesized K3TaO2F4:Mn4+ phosphor exhibited clear edges and corners with particle size of 1.5−2.0 μm, which is not enough for single crystal measurement. The elemental composition analysis of the K3TaO2F4:Mn4+ phosphor was quantitatively conducted using energy-dispersive spectrometry (EDS) and is exhibited in Figure 4b. It can be clearly seen that the peaks of K, Ta, O, F, and Mn are identified in the EDS spectrum of K3TaO2F4:Mn4+. Moreover, the atom percentages of K, Ta, O, and F are approximately 23.77%, 9.59%, 18.13%, and 35.04%, respectively, which is very close to 3:1:2:4, i.e., the stoichiometric atom ratio composition of K 3 TaO 2F 4. The elemental distributions maps of K/Ta/O/F/Mn are shown in Figure 4c. Luminescence Properties at Room Temperature. Because of the strong ligand-field stabilization energy of Mn4+ in the 6-fold coordination, Mn4+ prefers to stay in the distorted octahedron center site of the host. The luminescent behavior of Mn4+ in an octahedral crystal field can be interpreted by the Tanabe−Sugano energy diagram, as shown in Figure 5a.41,42 The luminescence properties of the above obtained K3TaO2F4:Mn4+ product were examined at room temperature as shown in Figure 5b. There are two broad bands in the excitation spectra from 300 to 500 nm with a peak position of 360 and 460 nm, respectively, which are

Table 2. Rietveld Refinement of X-ray Diffraction Data of K3TaO2F4 formula cryst syst space group lattice parameter a in Å lattice parameter c in Å cell volume in Å3 formula units per cell Z structure refinement radiation temp in K profile range no. of data points profile function R-Factors Rp Rwp Rexp GOF

bond length

C

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 2. Rietveld refinements of K3TaO2F4. The observed pattern (blue dots), calculated pattern (red line), and the different lines (gray line) are shown.

K3TaO2F4:Mn4+ were calculated as x = 0.684 and y = 0.315 based on the emission spectra, which are very close to the red standard values (0.67, 0.33) set by National Television Systems Committee (NTSC). The red phosphor K3TaO2F4:Mn4+ shows high color purity which can be calculated by the following equation: color purity =

(x − xi)2 + (y − yi )2 (xd − xi)2 + (yd − yi )2

× 100% (2)

where (x, y) is the color coordinates of the phosphor; (xi, yi) is the CIE of an equal-energy illuminant, and its value is (0.3333, 0.3333); and (xd, yd) is the chromaticity coordinates corresponding to the dominant wavelength of the light source. The color purity is calculated to be about 95%. From the luminescence photograph of the K3TaO2F4:Mn4+, the sample emits obvious brilliant red light under blue light illumination, which indicates that K3TaO2F4:Mn4+ red phosphor has potential in indoor illumination and other fields. The absolute quantum efficiency of K3TaO2F4:Mn4+ red phosphor is found to be 23.4% under 460 nm excitation. In addition, the blue excitation band is stronger than the ultraviolet excitation band (∼360 nm), which matches the emission peak of LED blue chip (∼460 nm), so that this red phosphor can be efficiently excited by the blue light from the InGaN chip. To obtain highly efficient phosphors, we investigated the effect of the doping amount of Mn4+ on the PL performance. The PL spectra of the K3Ta1−xO2F4:xMn4+ (x = 0.0573, 0.0669, 0.0692, 0.0745, 0.0770, 0.0806) samples excited at 460 nm are shown in Figure 6, and the relationship between normalized integrated PL intensity and Mn4+ doping concentration is shown in the inset. Under 460 nm excitation, all of the phosphors emit the typical seven sharp lines located at 597, 607, 612, 620, 630, 633, and 645 nm, corresponding to the transitions of anti-Stokes ν3(t1u), ν4(t1u), and ν6(t2u), zero phonon line (ZPL), and Stokes ν6(t2u), ν4(t1u), and ν3(t1u) vibronic modes, which are attributed to the spin-forbidden 2Eg → 4A2g transition of Mn4+ and its vibronic sidebands. As shown in the inset, the integrated intensity of the Mn4+ concentration function is constructed, which represents the change tendency of the luminescence intensity under different activator contents. With increasing Mn4+ content, the luminescence intensity of K3Ta1−xO2F4:xMn4+ increases gradually until the Mn4+ concentration value reached 6.92 mol %. When Mn4+ concentration exceeds 6.92 mol %,

Figure 3. Crystal structure scheme of K3TaO2F4.

Figure 4. (a) SEM of K 3 TaO2 F 4 :Mn 4+ . (b) EDS data of K3TaO2F4:Mn4+. (c)Elemental distributions of K/Ta/O/F/Mn by EDX mapping on the K3TaO2F4:Mn4+ particles.

attributable to the spin-allowed and parity-forbidden transitions 4A2g → 4T2g and 4A2g → 4T1g of Mn4+ ions. The corresponding emission spectrum consists of several sharp peaks located in the red region, originating from the spinforbidden 2Eg → 4A2g transitions of Mn4+. Figure 5c illustrates the CIE chromaticity diagram of the K 3 TaO 2 F 4 :Mn 4+ phosphor. The corresponding color coordinates of D

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 5. (a) Tanabe−Sugano energy diagram for Mn4+ (3d3) in an octahedral crystal field. (b) PLE (blue line) and PL (red line) spectra. (c) CIE chromaticity coordinates of the K3TaO2F4:Mn4+ product recorded at 293 K (λem = 630 nm, λex = 460 nm). Digital image of the K3TaO2F4:Mn4+ phosphor under blue lamp (460 nm) irradiation.

Figure 6. PL spectra for the K3TaO2F4:Mn4+ products prepared with different molar ratios of K 2 MnF 6 . The inset shows Mn 4+ concentration-dependent integrating intensity of K3TaO2F4:Mn4+.

Figure 7. Room-temperature PL decay curves of K3TaO2F4 doped with different Mn4+ concentrations.

concentration quenching occurs between Mn4+ ions, resulting in a decrease in luminescence intensity.43 Generally, the ZPL intensity is related to the Mn 4+ centrosymmetric environment, and lower symmetry leads to stronger ZPL intensity. In the Mn4+-doped Na2WO2F4, the ZPL intensity was higher than the phonon sidebands, but in the case for Mn4+-doped K3TaO2F4, the ZPL intensity was lower than the phonon sidebands.33 This feature is consistent with the structural analysis result; the [MnOF5]3− octahedron in K3TaO2F4:Mn4+ holds a higher symmetry C4v than the C2v [MnO2F4]3− in Na2WO2F4:Mn4+. The PL lifetime is strongly dependent on the activator concentration, and determining the PL lifetime is one of the important factors for phosphors. Figure 7 shows the concentration-dependent luminescence decay curves of K3TaO2F4:Mn4+ red phosphor obtained by monitoring the 630 nm emission under excitation at 460 nm. The PL decay curves fit well with a single-order exponential decay mode by the following equation: It = I0 exp( − t /τ )

(3)

where I0 and It are the luminescence intensities at time t0 and t, respectively; and τ is the decay time. The value of τ decreases from 4.24 to 3.87 ms as the Mn4+ concentration increases from 5.73 to 8.06 mol %, which is because of the gradual increase in nonradiative transition between the Mn4+ ion.44 Temperature-Dependent PL Properties. The temperature-dependent emission intensity of the K3TaO2F4:Mn4+ (6.92 mol %) is indicated in Figure 8. Figure 8a,b shows the

Figure 8. Temperature-dependent emission spectrum of K3TaO2F4:Mn4+ (6.92 mol %). (a) Heating up from 298 to 473 K. (b) Cooling down from 473 to 298 K. The insets in parts a and b show the relationship between integrated luminescence intensity and temperature.

E

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 9. Current-dependent photoelectric properties of warm WLED under different driven currents: (a) EL spectra, (b) CIE chromaticity coordinates, (c) CCT variations, and (d) magnification of the CIE.

Å, V = 354.57(5) Å3, and Z = 2. In the range from 300 to 500 nm, this phosphor exhibits a broadband excitation. An ideal narrow band emission is obtained peaking at 630 nm. The PL properties of the phosphors were optimized by varying the Mn4+ concentration, temperature, and drive current. Moreover, K3TaO2F4:Mn4+ exhibits a good thermal and color stability against thermal impact over the temperature range 300−500 K. The Ra and CCT of the fabricated WLED under 350 mA forward-bias current are 93.0 and 3488 K, respectively. The WLED device shows excellent stability in chromaticity coordinates and CCT with the drive current varying from 20 to 350 mA. All of these results imply that the K3TaO2F4:Mn4+ red-emitting phosphor has potential applications in warm WLEDs.

heating up and cooling down process among 298−473 K, respectively. A red-shift of the Mn4+ emission band with the temperature increases. When the temperature is raised to 423 K, the emission intensity has only 12.6% of the initial intensity. Moreover, both emission intensities of K3TaO2F4:Mn4+ (6.92 mol %) successfully recover to the initial state after cooling back to 298 K proving the considerable stability. Warm WLED Application. For a further effective evaluation of the luminescence characteristics, a warm LED was fabricated using a 450 nm blue LED chip and a mixture of the commercial yellow YAG:Ce3+ phosphor and as-synthesized K3TaO2F4:Mn4+ (6.92 mol %) red phosphor under different driven currents. The LED was recorded under drive currents between 20 and 350 mA and is shown in Figure 9a, and Table S2 provides the parameters of the LED device under different drive currents such as CCT, Ra, R9, and CIE coordinate. The WLED spectrum consists of three emission bands of 450, 560, and 630 nm. Meanwhile, there is no significant change in the band shape and position of the emission peak when the drive current is increased from 20 to 350 mA. In addition, the emission intensity and R9 would also be slightly increased as the drive current increases. Consequently, variations of small fluctuations in CIE chromaticity coordinates, magnification of the CIE, and CCT of WLEDs are shown in Figure 9b−d. WLEDs exhibit high color quality (CRI, Ra > 80; CCT < 4500 K), and the prototype device emits warm white light under 350 mA forward-bias current with a high color quality (CCT = 3488 K, Ra = 93.0, R9 = 90). These results indicate that the K 3 TaO 2 F4 :Mn4+ red phosphor is suitable as the red component for warm WLEDs.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b03577. Bond-valence sum and coordination and the parameters of the LED under different drive currents (PDF) Accession Codes

CCDC 1886870 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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CONCLUSION In summary, oxyfluoride red phosphor K3TaO2F4:Mn4+ was synthesized by a simple two-step synthesis method. The real crystal structure of oxyfluoride host K3TaO2F4 shows a tetragonal structure with space group I4/mmm (No. 139), and the lattice parameters are a = 6.3057(4) Å, c = 8.9173(6)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Xiaoming Wang: 0000-0002-1527-3496 F

DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

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Author Contributions

All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The project was sponsored by the National Natural Science Foundation of China (51672167 and 51272151), the Natural Science Foundation of Shaanxi Province (2018JQ5044, 2015JQ2041), Fundamental Research Funds for the Central Universities (GK201701011, GK201703020), and Science and Technology program of Xi’an (2017071CG/ RC034(SXSF004)).

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DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.8b03577 Inorg. Chem. XXXX, XXX, XXX−XXX