Luminescent Color-Adjustable Europium and Terbium Co-Doped Strontium Molybdate Phosphors Synthesized at Room Temperature Applied to Flexible Composite for LED Filter

: In this study, terbium and europium rare-earth ions were single-doped and co-doped to synthesized SoMoO 4 phosphor at room temperature. The samples prepared synthesized crystalline SrMoO 4 powder by the co-precipitation. Samples had a tetragonal structure in XRD analysis and d (112) spacing was changed by rare-earth doping. As the amount of rare earth added increased, a secondary phase appeared, and the structure changed. The synthesized SrMoO 4 :Tb 3+ phosphors showed a green light emission at 544 nm under 287 nm, SrMoO 4 :Eu 3+ phosphors showed a red light emission at 613 nm under 290 nm, and SrMoO 4 :[Eu 3+ ]/[Tb 3+ ] phosphor showed a yellow-white light emission at 544 and 613 nm when excited at 287 nm. The synthesized phosphor exhibited a change in green and red luminescence intensity based on the amount of Eu 3+ doped and showed strong red luminescence as the Eu 3+ doping increased. To use the SrMoO 4 :[Eu 3+ ]/[Tb 3+ ] phosphor with these characteristics in an LED color ﬁlter, a ﬂexible composite prepared by mixing with PDMS showed green, red, and yellow-white emission under a UV-lamp. is thought to be


Introduction
Recently, considerable research has been conducted to develop a white-light-emitting (wLED) diode with a high color-rendering index and excellent color reproducibility to replace incandescent and fluorescent lamps [1][2][3]. In general, wLEDs are manufactured in three ways. There is a method of applying yellow phosphor on the upper part of the blue LED chip or applying red and green phosphors on the upper part of the blue LED chip with the same method, and white light emission is achieved by applying red, green, and blue phosphor powder on the surface of the near-ultraviolet LED chip [4][5][6]. Among the emission wavelength ranges of the phosphors used in an LED chip, the intensity of red and green light emission is known as an important factor to increase the colorrendering index of the white light emission [7]. Oxidized compounds including molybdate, aluminate, borate, and silicate exhibit strong light absorbance in the ultraviolet region [8,9]. Among them, molybdate has a scheelite-type crystal structure and is considered as a good host material for light-emitting materials due to its excellent chemical and thermal stability [10][11][12]. In addition, molybdate compounds are important materials that can be applied to wLEDs, lasers, optical fibers, catalysts, etc., in addition to phosphors. Among molybdate compounds with these advantages, strontium molybdate (SrMoO 4 ) is doped with rare-earth ions and has a high luminous efficiency and chemical stability, thereby emerging as a phosphor material, and extensive research has been conducted on it [13][14][15][16]. Wang et al. produced a CaMoO 4 :Eu 3+ phosphor with a three-dimensional walnut-shaped shape by hydrothermal synthesis and reported that the size of the crystal grains increased as the heat treatment temperature was increased. In addition, when excited at 394 nm, red light emission was observed with a peak at 615 nm [17]. Du et al. synthesized a phosphor by doping rare-earth (RE) Eu 3+ ions into AMoO 4 (A = Mg, Ca, Sr, Ba) oxide with a tetragonal
Two beakers were prepared as shown in Figure 1. Next, 50 mL of distilled water and 1 mmol of barium acetate were added to the 'A' beaker and stirred. In the other 'B' beaker, 1 mmol of sodium molybdate and 50 mL of distilled water were added and stirred. The solution completely dissolved in the 'B' beaker was slowly poured into beaker 'A' and stirred for 2 h to react. After the 2 h, centrifugation was performed at 4000 rpm for 5 min to recover the white powder produced by the reaction. To remove any unreacted substances from the recovered powder, it was washed with 50 mL of distilled water, and the powder obtained after centrifugation under the same conditions was dried at 80 • C for 18 h. In the same way, a phosphor to which Tb 3+ and Eu 3+ ions single-doped and co-doped were added was synthesized, and the phosphor was prepared by single-doped (0.025 mmol) and changing the amount of [Eu 3+ ]/[Tb 3+ ]~(0.1, 0.2, 0.3, 0.5, 0.8) added to beaker 'A'.

Fabricated Flexible Composite for an LED
The flexible composite was prepared by mixing polydimethylsiloxane (PMDS) 10 wt.% and phosphor powder 1 wt.%, pouring them into a square-shaped frame and curing

Fabricated Flexible Composite for an LED
The flexible composite was prepared by mixing polydimethylsiloxane (PMDS) 10 wt.% and phosphor powder 1 wt.%, pouring them into a square-shaped frame and curing them at 80 • C for 2 h.

Characterization
The crystal structure of the SrMoO 4 and SrMoO 4 :RE 3+ powders synthesized by coprecipitation was measured at a diffraction angle of 10~70 • at a rate of 4 • per minute using an X-ray diffraction device (Cu-Kα radiation; 0.15406 nm, 40 kV and 20 mA, X'Pert PROMPD, XRD). Optical characteristics were irradiated at a photomultiplier voltage of 300 V using a fluorescence spectrometer (FS-2, Scinco) at room temperature. The fine shape of the surface and the size of the crystal particles were photographed by a field radial scanning electron microscope (FE-SEM, acceleration voltage of 3 kV, a working distance of 6.1 mm, and a magnification of 5 to 30 k), and the components were analyzed by energy dispersion X-ray spectroscopy (EDS, 5 min at an acceleration voltage of 15 kV with surface mapping).

Characteristics of SrMoO 4 and Single-Doped SrMoO 4
Figure 2a shows that the XRD data of SrMoO4 and SrMoO 4 :RE 3+ phosphor powder samples synthesized at room temperature by co-precipitation had a tetragonal (a = 5.394, b = 5.394, c = 12.020 Å) structure with main peaks at (112), (004), (200), (204), (220), (116), (312), and (224) which were found to be consistent with ICDD card No. 01-085-0586 [21]. The MXO 4 (M = Sr, X = Mo) particle precipitation -M 2+ cations act as electron pair receptors (Lewis acids) and XO 4 2− anions as electron pair donors (Lewis bases). The reaction between the two substances (M 2+ ← :XO 4 2− ) continues to bond. The lowest molecular orbital energy of the Lewis acid interacts with the highest molecular orbital energy of the Lewis base and eventually synthesizes the MXO 4 particles [22,23]. As the amount of Tb 3+ and Eu 3+ ions added was increased, the interplanar distance on the main peak (112) increased and then decreased ( Figure 2b). When the amount of rare-earth ions added is small, it is considered that the structure of the lattice is distorted when a space between the grids is opened, and the quantity of added ions is continuously increased due to rare-earth ions having a relatively large ionic radius [24,25].

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opened, and the quantity of added ions is continuously increased due to rare-earth ions having a relatively large ionic radius [24,25]. The particle size of the SrMoO4 and SrMoO4:RE 3+ samples was calculated using the (112) phase, which is the main peak, and the Scherrer's equation [26] as follows:   The particle size of the SrMoO 4 and SrMoO 4 :RE 3+ samples was calculated using the (112) phase, which is the main peak, and the Scherrer's equation [26] as follows: Here, n is Scherrer's constant 0.9; λ is the X-ray wavelength (0.15406 nm); θ is the diffraction angle, and B is the FWHM. SrMoO 4 was calculated to be about 100 nm, SrMoO 4 :Tb 3+ was calculated to be about 32 nm, and SrMoO 4 :Eu 3+ was calculated to be about 38 nm. Figure 3 shows the images taken by FE-SEM to observe the actual particle size and surface shape of the synthesized powder. SrMoO 4 was about 6.91 µm in the longitudinal direction and about 2.15 µm in the transverse direction. It was reported that the shuttle shape appeared clearly due to the growing Oswald's ripping. It was synthesized using a basic material and explained by the action of the base [27]. Cavalcante et al. reported that, in the case of particles synthesized by a high-energy reaction such as co-precipitation, aggregation between small particles is induced, and octahedral growth is induced in a basic atmosphere [28]. In Figure S1   The particle size of the SrMoO4 and SrMoO4:RE 3+ samples was calculated using the (112) phase, which is the main peak, and the Scherrer's equation [26] as follows: Here, n is Scherrer's constant 0.9; λ is the X-ray wavelength (0.15406 nm); θ is the diffraction angle, and B is the FWHM. SrMoO4 was calculated to be about 100 nm, SrMoO4:Tb 3+ was calculated to be about 32 nm, and SrMoO4:Eu 3+ was calculated to be about 38 nm. Figure 3 shows the images taken by FE-SEM to observe the actual particle size and surface shape of the synthesized powder. SrMoO4 was about 6.91 μm in the longitudinal direction and about 2.15 μm in the transverse direction. SrMoO4:Tb 3+ was about 0.31 μm and about 0.13 μm in the transverse direction. SrMoO4:Eu 3+ was about 0.41 μm and about 0.15 μm in the transverse direction. Both these samples had an octahedron-like shape and showed a longitudinal growth. According to Bharat et al., BaMoO4 synthesized by reacting with MoO4 −2 , a monomer of an oxyanion, grows in the longitudinal direction immediately after mixing the Ba aqueous solution and Mo aqueous solution. It was reported that the shuttle shape appeared clearly due to the growing Oswald's ripping. It was synthesized using a basic material and explained by the action of the base [27]. Cavalcante et al. reported that, in the case of particles synthesized by a high-energy reaction such as co-precipitation, aggregation between small particles is induced, and octahedral growth is induced in a basic atmosphere [28]. In Figure S1 (see Supplementary Materials), Sr, Mo, and O components and the addition of Tb and Eu were confirmed through SEM-EDS component analysis. SrMoO4 synthesized by co-precipitation as a basic material in this study is considered to have such a shape. The photoluminescence excitation (PLE) and photoluminescence   SrMoO 4 synthesized by co-precipitation as a basic material in this study is considered to have such a shape. The photoluminescence excitation (PLE) and photoluminescence (PL) spectra of the SrMoO 4 :Tb 3+ and SrMoO 4 :Eu 3+ phosphor are shown in Figure 4. Figure 4a shows the PLE spectrum (black line) of the SrMoO 4 :Tb 3+ phosphor monitored at an emission wavelength of 544 nm. The PLE spectrum of the SrMoO 4 :Tb 3+ phosphors contain a charge transfer state band (CTB) [29] and f-f transitions due to the presence of the Tb 3+ ions. CTB includes a broad band in the wavelength range of 220-325 nm. This band could rise due to the Mo-O and Tb-O charge transfer [30]. The f-f transitions associated with a number of weak peaks are located at 339, 350, 368, and 376 nm which are attributed to the 7 F 6 → 5 D 1 , 7 F 6 → 5 D 2 , 7 F 6 → 5 L 10 , and 7 F 6 → 5 D 3 transitions of the Tb 3+ ions, respectively. The PL spectrum (green line) was observed for the excitation wavelength 287 nm, stemming from Tb-O CTB [31]. The emission spectra contain five peaks centered at 487, 544, 585, 619, and 649 nm wavelengths, corresponding to the 5 D 4 → 7 F 6 , 5 D 4 → 7 F 5 , 5 D 4 → 7 F 4 , 5 D 4 → 7 F 3 , and 5 D 4 → 7 F 2 transitions [32]. In addition, among the above five components of emission spectra, the intensity of the green emission spectrum due to the 5 D 4 → 7 F 5 (544 nm) magnetic dipole transition was the strongest, and this emission intensity was the strongest due to the 5 D 4 → 7 F 6 (487 nm) electric dipole transition of the Tb 3+ ion. It was 3.29 times that of the blue emission intensity. From this result, it can be confirmed that the Tb 3+ ion located in the host crystal is located at an inversion symmetry Crystals 2022, 12, 552 5 of 11 site [33]. Figure 4b shows the results of the PLE (black line) and PL (red line) spectra when measured in the SrMoO 4 :Eu 3+ phosphor powder. SrMoO 4 :Eu 3+ phosphor controlled to an emission wavelength of 613 nm of PLE spectra was CTB observed between Mo-O ions with a wide bandgap over the region of 220-320 nm and a peak at 292 nm, and the other type of absorption signal is at 320~450 nm. These absorption peaks were 4f-4f transition signals of Eu 3+ ions. The PLE spectra monitored at the peaks at 361 ( 7 F 0 → 5 D 4 ), 381 ( 7 F 0 → 5 G 3 ), 393 ( 7 F 0 → 5 L 6 ), and 415 ( 7 F 0 → 5 D 3 ) nm are correspondingly transition signals of Eu 3+ ions located in the host crystal [34]. The PL spectrum by which the phosphor was measured excited 290 nm, showed the strongest absorption intensity. The phosphor powder was composed of an emission spectrum having the strongest emission intensity with a peak at a wavelength of 613 nm, a peak emission spectrum at 590 nm having relatively weak emission intensity, and an emission spectrum having peaks at 651 nm and 700 nm. Here, 613 nm is the signal induced by the 5 D 0 → 7 F 2 electric dipole transition, 590 nm is the 5 D 0 → 7 F 1 magnetic dipole transition, and the two red emission spectra (651 and 700 nm) are the 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 electric dipole signals. In this experiment, because the intensity of the red emission (613 nm) spectrum stemming from the 5 D 0 → 7 F 2 electric dipole transition was 9.89 times greater than the intensity of the orange emission (590 nm) from the 5 D 0 → 7 F 1 magnetic dipole transition, Eu 3+ ions in the host lattice were found to be located at the sites of inversion symmetry, not inversion symmetry [35,36]. magnetic dipole transition was the strongest, and this emission intensity was the strongest due to the 5 D4 → 7 F6 (487 nm) electric dipole transition of the Tb 3+ ion. It was 3.29 times that of the blue emission intensity. From this result, it can be confirmed that the Tb 3+ ion located in the host crystal is located at an inversion symmetry site [33]. Figure 4b shows the results of the PLE (black line) and PL (red line) spectra when measured in the SrMoO4:Eu 3+ phosphor powder. SrMoO4:Eu 3+ phosphor controlled to an emission wavelength of 613 nm of PLE spectra was CTB observed between Mo-O ions with a wide bandgap over the region of 220-320 nm and a peak at 292 nm, and the other type of absorption signal is at 320~450 nm. These absorption peaks were 4f-4f transition signals of Eu 3+ ions. The PLE spectra monitored at the peaks at 361 ( 7 F0 → 5 D4), 381 ( 7 F0 → 5 G3), 393 ( 7 F0 → 5 L6), and 415 ( 7 F0 → 5 D3) nm are correspondingly transition signals of Eu 3+ ions located in the host crystal [34]. The PL spectrum by which the phosphor was measured excited 290 nm, showed the strongest absorption intensity. The phosphor powder was composed of an emission spectrum having the strongest emission intensity with a peak at a wavelength of 613 nm, a peak emission spectrum at 590 nm having relatively weak emission intensity, and an emission spectrum having peaks at 651 nm and 700 nm. Here, 613 nm is the signal induced by the 5 D0 → 7 F2 electric dipole transition, 590 nm is the 5 D0 → 7 F magnetic dipole transition, and the two red emission spectra (651 and 700 nm) are the 5 D → 7 F3 and 5 D0 → 7 F4 electric dipole signals. In this experiment, because the intensity of the red emission (613 nm) spectrum stemming from the 5 D0 → 7 F2 electric dipole transition was 9.89 times greater than the intensity of the orange emission (590 nm) from the 5 D0 → 7 F1 magnetic dipole transition, Eu 3+ ions in the host lattice were found to be located at the sites of inversion symmetry, not inversion symmetry [35,36].

Characteristics of [Eu 3+ ]/[Tb 3+ ] Co-Doped SrMoO 4
The XRD pattern of the sample prepared by fixing Tb 3+ (2.5 mol%) ions and changing the amount of Eu 3+ ions added is shown in Figure 5. The XRD patterns of the secondary phase was observed as the Eu 3+ addition amount increased. As the amount of rare-earth ions added increased, a single oxide phase was detected without doping in the lattice, so the optimal rare-earth doping condition was considered to be [Eu 3+ ]/[Tb 3+ ]~0.3. In addition, excessive doping of rare-earth ions showed that d (112) spacing changed excessively (Figure 5b), so it was thought that excessive doping of rare-earth ions changed the crystal structure of SrMoO 4 and adversely affected the expression of a secondary phase. It was also thought to be the cause of the changes in the lattice constant due to the doping of rare-earth ions with relatively large ionic radii (r(Sr 2+ = 1.26 Å), r(Mo 6+ = 0.59 Å), r(Tb 3+ = 1.18 Å), r(Eu 3+ = 1.06 Å)) [37,38]. Additionally, as full width at half maximum (FWHM) tends to increase as the amount of rare-earth ions added in-creases, it is considered that excessive doping of rare earths affects the crystal structure and crystallinity.
[Eu 3+ ]/[Tb 3+ ]~0.3. In addition, excessive doping of rare-earth ions showed that d(112) spacing changed excessively (Figure 5b), so it was thought that excessive doping of rare-earth ions changed the crystal structure of SrMoO4 and adversely affected the expression of a secondary phase. It was also thought to be the cause of the changes in the lattice constant due to the doping of rare-earth ions with relatively large ionic radii (r(Sr 2+ = 1.26 Å), r(Mo 6+ = 0.59 Å), r(Tb 3+ = 1.18 Å), r(Eu 3+ = 1.06 Å)) [37,38]. Additionally, as full width at half maximum (FWHM) tends to increase as the amount of rare-earth ions added increases, it is considered that excessive doping of rare earths affects the crystal structure and crystallinity.   Figure S2). Figure 7 shows the PL spectrum measured by excitation of the synthesized SrMoO4:[Eu 3+ ]/[Tb 3+ ] phosphor powder with a wavelength of 287 nm while fixing Tb 3+ ions and changing the doping amount of Eu 3+ ions. In the [Eu 3+ ]/[Tb 3+ ]~0.1 samples, emission spectra of two types of activator ions were observed. In the first case, a green light emission signal with a peak at 544 nm and a blue light emission signal at 487 nm appeared due to electric dipole transition ( 5 D4 → 7 F5) and magnetic dipole transition ( 5 D4 → 7 F6) of the activator Tb 3+ ion [39], and the second was 619 nm due to the electric dipole transition of Eu 3+ ion. A red emission spectrum having peaks at 651 nm and 700 nm, due to the 5 D0 → 7 F3 and 5 D0 → 7 F4 transition of Eu 3+ ions with relatively weak emission intensity, was observed [40]. In this case, the intensity of green emission at 544 nm by Tb 3+ ions was about 3.5 times stronger than that of red emission at 619 nm by Eu 3+ ions. When the addition amount of Eu 3+ was increased, the intensity of the emission spectrum due to the transition of Tb 3+ ions decreased, the intensity of the emission spectrum due to the transition of Eu 3+ ions increased, and the intensity of the emission spectrum was reversed at [      In the first case, a green light emission signal with a peak at 544 nm and a blue light emission signal at 487 nm appeared due to electric dipole transition ( 5 D 4 → 7 F 5 ) and magnetic dipole transition ( 5 D 4 → 7 F 6 ) of the activator Tb 3+ ion [39], and the second was 619 nm due to the electric dipole transition of Eu 3+ ion. A red emission spectrum having peaks at 651 nm and 700 nm, due to the 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 transition of Eu 3+ ions with relatively weak emission intensity, was observed [40]. In this case, the intensity of green emission at 544 nm by Tb 3+ ions was about 3.5 times stronger than that of red emission at 619 nm by Eu 3+ ions. When the addition amount of Eu 3+ was increased, the intensity of the emission spectrum due to the transition of Tb 3+ ions decreased, the intensity of the emission spectrum due to the transition of Eu 3+ ions increased, and the intensity of the emission spectrum was reversed at [Eu 3+ ]/[Tb 3+ ]~0.8.   Figure 7b shows the change in the intensity of the emission wavelength according to the change in the amount of Eu 3+ ions added. As the addition amount of Eu 3+ ions increased, the main emission signal shifted from green to red emission, and it is believed that the emission energy was converted from Tb 3+ ions to Eu 3+ ions. The energy transfer efficiency from Tb 3+ ions to Eu 3+ ions can be calculated using the following equation [41].
Here, Io is the intensity of green and blue emission emitted by Tb 3+ ions from a phosphor doped with single Tb 3+ ions, and I is the intensity of emission from Tb 3+ ions from a phosphor doped with Tb 3+ and Eu 3+ ions simultaneously. As shown in Figure 7c, Figure 7b shows the change in the intensity of the emission wavelength according to the change in the amount of Eu 3+ ions added. As the addition amount of Eu 3+ ions increased, the main emission signal shifted from green to red emission, and it is believed that the emission energy was converted from Tb 3+ ions to Eu 3+ ions. The energy transfer efficiency from Tb 3+ ions to Eu 3+ ions can be calculated using the following equation [41].
Here, I 0 is the intensity of green and blue emission emitted by Tb 3+ ions from a phosphor doped with single Tb 3+ ions, and I is the intensity of emission from Tb 3+ ions from a phosphor doped with Tb 3+ and Eu 3+ ions simultaneously. As shown in Figure 7c, the energy transfer efficiency [42][43][44] from Tb 3+ ions to Eu 3+ ions increases as the doping concentration of Eu 3+ ions increases. The energy transfer efficiency increased from 23% to 70%, but the luminescence tax decreased due to the concentration-quenching phenomenon due to the addition of excessive rare earths. In addition, in the XRD data, a secondary phase  Figure 8 shows a photograph of a flexible composite made by mixing the synthesized phosphor powder with a PDMS polymer for use as an LED filter. The square-shaped complex appeared white in everyday light but showed unique luminescence properties depending on the doped rare-earth ion in the UV lamp. The complex of SrMoO 4 :Tb 3+ phosphor doped with Tb 3+ ions showed green, the complex of SrMoO 4 :Eu 3+ phosphor showed red, and the complex of SrMoO 4 :[Eu 3+ ]/[Tb 3+ ] phosphor showed yellow-white. SrMoO 4 phosphors, which have flexibility due to the PDMS polymer and can be used as various LED filters depending on the type of doped rare earth, were synthesized and their applications were presented. To find out the resistance of the fabricated composite to temperature and humidity, water was put in a beaker and the composite was immersed. The beaker was placed in an 80-degree oven for 72 h and the change in light-emitting characteristics was examined through PL measurement. As shown in Figure 8b, there was no significant change in the light emission intensity, so it is thought to be able to withstand temperature and humidity.

Fabricated Flexible Composite for LED Filter
was found from [Eu 3+ ]/[Tb 3+ ]~0.5 and the crystal structure was changed. It is believed the addition of excessive rare earths changes the structure and luminescence proper In the Commission Internationale de L'Eclairage 1931 (CIE 1931) [45] Figure 8 shows a photograph of a flexible composite made by mixing the synthes phosphor powder with a PDMS polymer for use as an LED filter. The square-shaped c plex appeared white in everyday light but showed unique luminescence properties pending on the doped rare-earth ion in the UV lamp. The complex of SrMoO4:Tb 3+ p phor doped with Tb 3+ ions showed green, the complex of SrMoO4:Eu 3+ phosphor sho red, and the complex of SrMoO4:[Eu 3+ ]/[Tb 3+ ] phosphor showed yellow-white. SrM phosphors, which have flexibility due to the PDMS polymer and can be used as var LED filters depending on the type of doped rare earth, were synthesized and their ap cations were presented. To find out the resistance of the fabricated composite to tem ature and humidity, water was put in a beaker and the composite was immersed. beaker was placed in an 80-degree oven for 72 h and the change in light-emitting cha teristics was examined through PL measurement. As shown in Figure 8b, there wa significant change in the light emission intensity, so it is thought to be able to withs temperature and humidity.

Conclusions
Crystalline SrMoO 4 was synthesized at room temperature using the coprecipitation method. The synthesized SrMoO 4 was able to confirm the main peak (112) phase in XRD analysis and was consistent with ICDD card No. 01-085-0586. Tb 3+ and Eu 3+ ions were doped, respectively, to make the synthesized SrMoO4 a host phosphor. The doped sample showed green and red light emission as rare-earth ions with a large ion radius were doped, and the lattice constant of the surface of the main peak (112) was increased. For use as a white-light-emitting phosphor, SrMoO 4 was co-doped with Tb 3+ and Eu 3+ . The phosphor having two rare earths co-doped with each other had a fixed Tb 3+ addition amount, the crystal structure of SrMoO 4 changed according to a change in the Eu 3+ addition amount, and an E 2 O 3 phase, which was a secondary phase, was found when the Eu 3+ ion added amount was increased. In addition, as the amount of Eu 3+ ions added increased, the emission characteristics changed from green to red, and yellow-white emission was shown when [Eu 3+ ]/[Tb 3+ ]~0.5. The synthesized phosphor had an octahedron shape and a size of about 0.4 um. The composite manufactured by mixing the synthesized phosphor and PDMS together showed green, red, and yellow-white luminescence and had flexible characteristics. In addition, it showed resistance that the emission characteristics did not change even when exposed to temperature and humidity.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.

Conflicts of Interest:
The author declares no conflict of interest.