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POLYSULFIDE UPCONVERSION PHOSPHOR

20230242815 · 2023-08-03

    Inventors

    Cpc classification

    International classification

    Abstract

    The present invention relates to a polysulfide upconversion phosphor, and belongs to the field of new optical function materials. The phosphor uses polysulfide as a substrate and rare earth ions as activators, and has a general formula of composition: mA.sub.2S.Math.nBS.Math.kC.sub.2-xS.sub.3:D.sub.x. The upconversion phosphor provided by the present invention can emit ultraviolet, blue, blue-green, green, red and near-infrared light when excited by near infrared light at 750-1650 nm. Because the upconversion phosphor provided by the present invention uses polysulfide with low phonon energy and symmetry as a substrate material, and optimizes rare earth ions to be doped into the matrix material as luminescence centers, the upconversion phosphor has higher upconversion luminescence efficiency and safety and wider application range compared with industrial NaYF.sub.4:Yb, Er material.

    Claims

    1. A polysulfide upconversion phosphor, wherein a general formula of composition of the polysulfide upconversion phosphor is: mA.sub.2S.Math.nBS.Math.kC.sub.2-xS.sub.3:D.sub.x; A is one or more than one of Li, Na, K, Rb and Cs, and B is one or more than one of Be, Mg, Ca, Sr, Ba, Zn, Cd and Cs; C is one or more than one of La, Gd, Lu, Y, Sc, Al, Ga and Bi; D is one or more than one of Ho, Er, Tm and Pr, and Mo, W, Ce, Sm, Tb, Yb, Eu or Nd is co-doped in D; m, n, k and x are mole fractions, m=0-2, n=0-6, k=0.3-2.5, and x=0.0001-2; wherein when m=0-0.2 and n=0-0.1, k value is 0.9-1.1; wherein when n=0-0.1, m value is 0.8-1.2 and k value is 0.4-0.6; wherein when m=0-0.2 and n value is 0.8-1.2, k value is 0.8-1.2; wherein when m=0-0.2 and n value is 4.5-5.5, k value is 1.8-2.2; wherein when D contains Er, x value is 0.05-2; the range of excitation wavelengths is 1450-1600 nm or 780-860 nm; and one or more than one of the excitation wavelengths is used; wherein when D contains Ho, x value is 0.02-2 and the used range of excitation wavelengths is 1100-1190 nm; and wherein when D contains Tm, x value is 0.01-2; the ranges of excitation wavelengths are 1180-1260 nm and 760-850 nm; and two excitation wavelengths are used separately or simultaneously.

    2-8. (canceled)

    9. The polysulfide upconversion phosphor according to claim 1, wherein the phosphor emits ultraviolet, blue, blue-green, green, red and near-infrared light when excited by near infrared light at 750-1650 nm.

    Description

    DESCRIPTION OF DRAWINGS

    [0023] FIG. 1 shows the emission spectrum of NaY.sub.0.9S.sub.2:Er.sub.0.1 sample under 1550 nm excitation in embodiment 18 of the present invention.

    [0024] FIG. 2 is a data diagram of NaY.sub.0.9S.sub.2:Er.sub.0.1 and NaYF.sub.4:Yb, Er in embodiment 18 of the present invention, wherein (a) is a comparison diagram of brightness data, (b) is a curve graph of change of brightness with the excitation power of 980 and 1550 nm lasers, and (c) is a luminescence photo of NaY.sub.0.9S.sub.2:Er.sub.0.1 under the excitation of 980 and 1550 nm lasers.

    [0025] FIG. 3 shows the emission spectrum of NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1, Er.sub.0.1 sample under 980 nm excitation in embodiment 60 of the present invention.

    [0026] FIG. 4 shows the emission spectrum of NaGd.sub.0.9S.sub.2:Er.sub.0.1@NaGd.sub.0.78S.sub.2:Er.sub.0.18, Ho.sub.0.05 sample under 980 nm excitation in embodiment 61 of the present invention.

    [0027] FIG. 5 shows the emission spectrum of NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10@NaY.sub.0.89S.sub.2:Yb.sub.0.08, Nd.sub.0.01, Tm.sub.0.02 sample under 980 nm excitation in embodiment 62 of the present invention.

    DETAILED DESCRIPTION

    [0028] Different compositions and luminescence properties of the polysulfide of the present invention are described below through specific embodiments.

    [0029] Reference embodiment 1:green upconversion phosphor of commercial β-NaYF.sub.4:Yb,Er. Reference embodiment 2:blue upconversion phosphor of commercial β-NaYF.sub.4:Yb,Tm. Reference embodiment 3:red upconversion phosphor of commercial Y.sub.2O.sub.3:Yb,Er.

    [0030] The sample of the present invention is prepared by a solid phase reaction method, and raw materials are weighed according to the molar ratio of the constituent elements. The raw materials may be oxides, carbonates, oxalates, nitrates, acetate and sulfates of the elements mentioned in the technical solution. The raw materials are porphyrized and mixed evenly by a dry mixing method, put into a crucible, placed in a high temperature furnace, and calcined in a vulcanization atmosphere (such as H.sub.2S and CS.sub.2) at 900-1400° C. for 1-50 h. The calcination time is adjusted according to the amount of the materials. To improve the brightness, a small amount of cosolvent, such as 0-20 wt % of AF and/or BF.sub.2, including NH.sub.4Cl, NH.sub.4F, MgF.sub.2, CaF.sub.2, SrF.sub.2 and BaF.sub.2, can be added to the raw materials, which can significantly improve the upconversion luminescence efficiency.

    [0031] The present invention measures the luminescence brightness or luminescence intensity of the sample to evaluate the luminescence efficiency. The specific measurement method of the luminescence brightness comprises: placing the sample in a black disk with a diameter of 10 mm and a depth of 5 mm, and flattening the sample with a glass sheet to eliminate the influence caused by scattering. An excitation light source is a semiconductor laser. For visible light samples, after the sample is irradiated by a laser, the brightness of the sample is measured by a brightness meter. Commercial β-NaYF.sub.4:Yb,Er (green), β-NaYF.sub.4:Yb,Tm (blue) and Y.sub.2O.sub.3:Yb,Er (red), which have the highest upconversion luminescence efficiency at present, are used as reference samples. For invisible samples, compared with a method for measuring the luminescence intensity by a spectrometer, all test conditions are consistent in a set of embodiments.

    [0032] Embodiment 1: Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) are used as initial raw materials. The raw materials are weighed according to a chemical formula ratio Y.sub.1.9S.sub.3:Er.sub.0.01, fully ground for 30 minutes, and placed in a quartz tube; and then the quartz tube is placed in a resistance furnace. CS.sub.2 bubbles are introduced by Ar gas, or H.sub.2S gas containing Ar carrier gas is directly used; then, the sample is heated to 1050° C. at a speed of 10° C./min, preserved at the temperature for 2 hours and cooled to room temperature; and the sample is ground to obtain a target product. A 1500 nm laser is used as the excitation source and compared with reference embodiment 1. The performance indexes are shown in the following table.

    [0033] Embodiment 2 to embodiment 17 can be obtained by the similar methods.

    TABLE-US-00001 Relative No. m n k x Brightness Reference 100 embodiment 1 Embodiment 1 0 0 C = Y, k = 1 0.01 89 Embodiment 2 0 0 C = Y, k = 0.9 0.05 127 Embodiment 3 0 0 C = Y, k = 1 0.10 133 Embodiment 4 0 0 C = Y, k = 1.1 0.15 136 Embodiment 5 0 0 C = Y, k = 1 0.20 138 Embodiment 6 0 0 C = Y, k = 1 0.40 102 Embodiment 7 A = Li, m = 0.05 0 C = Y, k = 1 0.20 165 Embodiment 8 A = Na, m = 0.10 0 C = Y, k = 1 0.20 157 Embodiment 9 A = K, m = 0.20 0 C = Y, k = 1 0.20 153 Embodiment 10 0 B = Mg, n = 0.02 C = Y, k = 1.1 0.20 146 Embodiment 11 0 B = Ca, n = 0.04 C = Y, k = 1 0.20 144 Embodiment 12 0 B = Sr, n = 0.08 C = Y, k = 1 0.20 141 Embodiment 13 A = Li, m = 0.05 B = Mg, n = 0.02 C = Y, k = 0.9 0.20 169 Embodiment 14 A = Na, m = 0.05 B = Mg, n = 0.02 C = Gd, k = 1 0.20 147 Embodiment 15 A = K, m = 0.05 B = Mg, n = 0.02 C = Lu, k = 1 0.20 172 Embodiment 16 A = Li, m = 0.05 B = Mg, n = 0.02 C = La, k = 1 0.20 153 Embodiment 17 A = Li, m = 0.05 B = Mg, n = 0.02 C = Sc, k = 1 0.20 148

    [0034] The influences of other parameters not listed in embodiments 1-17 on luminescence colors, luminescence intensity and thermal properties can also be obtained by the methods similar to those of embodiments 1-17. When A=Rb or Cs, there is a similar result as A=K, but Rb and Cs are more expensive. When A is used in combination, the performance is better. The combination of A=Li and K can make the particle size of the product more uniform. Under the condition of keeping the luminescence intensity unchanged, the reaction temperature can be appropriately reduced by 50-100° C. When B=Be, Ba, or Cd, there are similar results as B=Ca, but considering the environmental protection requirements, products containing these elements may encounter difficulties when applied. When B=Zn, the flow rate and the reducibility of a carrier gas atmosphere should be controlled. When C=Al, Ga or Bi, it is usually used for replacing no more than 30% of La, Gd, Lu, Y or Sc, which can improve the luminescence intensity by about 5-13%. When D=Er, the used ranges of the excitation wavelengths are 1450-1600 nm, 920-1150 nm and 780-860 nm. The three excitation wavelengths can be used separately or simultaneously, and the effect is similar to that of the 1500 nm excitation light source. The selection of the wavelengths of the excitation light source depends on the application conditions and the laser wavelengths available in bulk on the market. For luminescence brightness, infrared light in the wavelength range of 1450-1600 nm is used>infrared light in the wavelength range of 920-1150 nm is used>infrared light in the wavelength range of 780-860 nm is used. Especially, infrared light in the range of 1450-1600 nm has a safe wavelength for human eyes and has the highest brightness, which is particularly advantageous for application. In the above embodiment, a small amount of cosolvent is added to the raw materials, such as 0-20 wt % of NH.sub.4Cl, NH.sub.4F, MgF.sub.2, CaF.sub.2, SrF.sub.2, BaF.sub.2, etc., which can further improve the luminescence brightness by 5-28%. The combined use realizes better performance.

    [0035] When RE=Er, the physical properties of the material can also be changed through combination and co-doping with other RE ions, such as luminescence colors and endothermic performance. If a small amount of (x=0.01-0.3) Mo and W is added, the red luminescence component in the luminescence spectrum can be significantly reduced, and the color purity of green luminescence can be increased by 2-10 times. If Ho, Tm or Pr is added, the red luminescence component in the luminescence spectrum can be increased; the color purity of red luminescence can be increased by 2-15 times; and the luminescence brightness is 110-180% of that of reference embodiment 3 under the same excitation condition. At the same time the color purity of red luminescence is 200-300% of that of reference embodiment 3. If Yb, Ce, Sm, Tb, Eu or Nd is added, the thermal properties can be significantly enhanced and the luminescence colors can be changed; and at the same power density, the temperature rise of the sample can be more than doubled.

    [0036] When RE=Ho, the excitation wavelength can be changed to 1100-1190 nm, and the color purity of the green luminescence is more than 150% higher than that of RE=Er. When RE=Tm, the excitation wavelength can be changed to 1180-1260 nm and 760-850 nm, and the brightness of green luminescence is 150-300% of that of reference embodiment 2 under the same excitation conditions, thereby widening the application range. Through further combination with other RE, panchromatic luminescence can be obtained, or the color purity can be adjusted.

    [0037] When the values of m, n, k and x are beyond the range of embodiments 1-17, such as m=0.2-2, n=0.1-6, k=0.3-0.9, k=1.1-2.5 and x=0.2-2, the sample also has a good luminescence effect, but the luminescence intensity is reduced by 5-53% compared with embodiments 1-17 under the same conditions.

    [0038] Embodiment 18: NaY.sub.0.9S.sub.2:Er.sub.0.1

    [0039] Y.sub.2O.sub.3 (99.99%), Er.sub.2O.sub.3 (99.99%) and Na.sub.2CO.sub.3 (99.99%) are used as initial raw materials. The raw materials are weighed according to a chemical formula ratio NaY.sub.0.9S.sub.2:Er.sub.0.1, fully ground for 30 minutes, and placed in a quartz tube; and then the quartz tube is placed in a resistance furnace. CS.sub.2 bubbles are introduced by Ar gas; then, the sample is heated to 1050° C. at a speed of 10° C./min, preserved at the temperature for 2 hours and cooled to room temperature; and the sample is ground to obtain a target product.

    [0040] FIG. 1 shows the upconversion luminescence spectrum of NaY.sub.0.9S.sub.2:Er.sub.0.1 sample under 1550 nm excitation. It can be seen that the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample shows green emission at 512-578 nm band and red emission at 640-698 nm, corresponding to Er.sup.3+ transitions at energy levels .sup.4S.sub.3/2.fwdarw..sup.4I.sub.15/2, .sup.2H.sub.11/2.fwdarw..sup.4I.sub.15/2 and .sup.4F.sub.9/2.fwdarw..sup.4I.sub.15/2, respectively.

    [0041] To further evaluate the upconversion luminescence performance of NaY.sub.0.9S.sub.2:Er.sub.0.1, the luminescence brightness data of the NaY.sub.0.9S.sub.2:Er.sub.0.1 samples under the 980 nm and 1550 nm excitation of the same power are compared with reference embodiment 1 (FIG. 2). Under 1550 nm excitation, NaY.sub.0.9S.sub.2:Er.sub.0.1 has very high upconversion luminescence efficiency, and the brightness is −60 times that of 980 nm excitation, and even more than twice that of commercial NaYF.sub.4:Yb, Er under 980 nm excitation.

    [0042] Embodiment 19 to embodiment 37 can be obtained by the similar methods.

    TABLE-US-00002 Relative No. m n k x Brightness Reference 100 embodiment 1 Embodiment 19 A = 0.8 Li 0 C = Y, k = 0.4 0.01 155 Embodiment 20 A = 0.8 Na 0 C = Y, k = 0.4 0.05 172 Embodiment 21 A = 0.8 K 0 C = Y, k = 0.4 0.10 225 Embodiment 22 A = 0.4 Na, 0.4 K 0 C = Y, k = 0.4 0.50 210 Embodiment 23 A = 0.1 Li, 0.7 Na 0 C = Y, k = 0.4 1.00 183 Embodiment 24 A = 0.8 Na 0 C = Y, k = 0.4 2.00 160 Embodiment 25 A = 0.8 Na 0 C = Y, k = 0.5 0.10 262 Embodiment 26 A = 0.8 Na 0 C = Y, k = 0.6 0.10 215 Embodiment 27 A = 1.0 Na 0 C = Y, k = 0.4 0.10 245 Embodiment 28 A = 1.0 Na 0 C = Y, k = 0.5 0.10 289 Embodiment 29 A = 1.0 Na 0 C = Y, k = 0.6 0.10 230 Embodiment 30 A = 1.2 Na 0 C = Y, k = 0.6 0.10 196 Embodiment 31 A = 0.8 Na B = Ca, 0.01 C = Y, k = 0.4 0.50 272 Embodiment 32 A = 0.8 Na B = Mg, 0.05 C = Y, k = 0.5 0.50 277 Embodiment 33 A = 0.8 Na B = Sr, 0.1 C = Y, k = 0.6 0.50 251 Embodiment 34 A = 1.0 Na B = Ca, 0.1 C = Y, k = 0.4 0.50 295 Embodiment 35 A = 1.0 Na B = Ca, 0.1 C = La, k = 0.4 0.50 295 Embodiment 36 A = 1.0 Na B = Ca, 0.1 C = Gd, k = 0.5 0.50 299 Embodiment 37 A = 1.0 Na B = Ca, 0.1 C = Lu, k = 0.6 0.50 258

    [0043] The influences of other parameters not listed in embodiments 19-37 on luminescence colors, luminescence intensity and thermal properties can also be obtained by the methods similar to those of embodiments 19-37. The effects are similar to the example listed below in embodiments 1-17, but the luminescence intensity is higher than that listed below in embodiments 1-17 by 12-35%.

    [0044] Embodiment 38 to embodiment 47 can be obtained by the similar methods to embodiments 19-37.

    TABLE-US-00003 Relative No. m n k x Brightness Reference 100 embodiment 1 Embodiment 38 0 B = 0.8 Ca C = Y, k = 0.8 0.01 105 Embodiment 39 0 B = 0.7Ca, 0.1Mg C = Y, k = 1.0 0.05 132 Embodiment 40 0 B = 0.8 Sr C = Y, k = 1.0 0.10 169 Embodiment 41 0 B = 1.0 Ca C = Y, k = 1.2 0.50 155 Embodiment 42 0 B = 1.2 Ca C = Y, k = 1.0 1.00 118 Embodiment 43 0 B = 0.8 Ca C = Y, k = 1.0 2.00 105 Embodiment 44 A = 0.05 Na B = 1.0 Ca C = Y, k = 1.05 0.20 183 Embodiment 45 A = 0.1 Li B = 1.0 Sr C = La, k = 1.0 0.20 207 Embodiment 46 A = 0.2 K B = 1.0 Ca C = Gd k = 1.0 0.20 214 Embodiment 47 A = 0.02Na, 0.03 K B = 1.0 Ca C = Lu, k = 1.3 0.20 196

    [0045] The influences of other parameters not listed in embodiments 38-47 on luminescence colors, luminescence intensity and thermal properties can also be obtained by the methods similar to those of embodiments 38-47. The effects are similar to the example listed below in embodiments 1-17, but the luminescence intensity is higher than that listed below in embodiments 1-17 by 7-23%.

    [0046] Embodiment 48 to embodiment 59 can be obtained by the similar methods to embodiments 38-47.

    TABLE-US-00004 Relative No. m n k x Brightness Reference 100 embodiment 1 Embodiment 48 0 B = 4.5 Ca C = Y, k = 1.8 0.01 132 Embodiment 49 0 B = 5.0 Sr C = Y, k = 2.0 0.05 151 Embodiment 50 0 B = 5.5 Ba C = Y, k = 2.2 0.10 243 Embodiment 51 0 B = 4.5 Ca C = Y, k = 2.0 0.50 190 Embodiment 52 0 B = 5.0 Sr C = Y, k = 2.0 1.00 214 Embodiment 53 0 B = 5.5 Ba C = Y, k = 2.0 2.00 88 Embodiment 54 A = Li, m = 0.05 B = 4.5 Ca C = Y, k = 2.0 0.20 294 Embodiment 55 A = Na, m = 0.10 B = 5.0 Sr C = Y, k = 2.0 0.20 287 Embodiment 56 A = K, m = 0.20 B = 5.5 Ba C = Y, k = 2.0 0.20 276 Embodiment 57 A = 0.02 Li, 0.03 Na B = 0.2 Mg, 4.5 Ca C = La, k = 2.0 0.20 325 Embodiment 59 0 B = 5.0 Ca C = Gd, k = 2.0 0.20 236 Embodiment 59 0 B = 5.0 Ca C = Lu, k = 2.0 0.20 198

    [0047] The influences of other parameters not listed in embodiments 48-59 on luminescence colors, luminescence intensity and thermal properties can also be obtained by the methods similar to those of embodiments 48-59. The effects are similar to the example listed below in embodiments 1-17.

    [0048] Embodiment 60: NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1, Er.sub.0.1

    [0049] Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaY.sub.0.9S.sub.2:Er.sub.0.1 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample. Y.sub.2O.sub.3 (99.99%), Yb.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.9S.sub.2: Er.sub.0.1 is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaY.sub.0.9S.sub.2: Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1, Er.sub.0.1 sample.

    [0050] FIG. 3 shows the upconversion luminescence spectrum of NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1, Er.sub.0.1 sample under 1550 nm excitation. The spectrum is formed by two groups of bands in the visible part. Green emission at 512-578 nm band and red emission at 640-698 nm correspond to transitions of Er.sup.3+ ions at .sup.4S.sub.3/2.fwdarw..sup.4I.sub.15/2, .sup.2H.sub.11/2.fwdarw.4I15/2 and .sup.4F.sub.9/2.fwdarw..sup.4I15/2, respectively. Compared with the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample, NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1, Er.sub.0.1 is similar in peak pattern, but the relative emission intensity of red and green light bands is quite different. NaY.sub.0.9S.sub.2:Er.sub.0.1 shows strong green light and weak red light, and NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.8S.sub.2:Yb.sub.0.1 and Er.sub.0.1 shows strong red light and weak green light. Under the same excitation conditions, the pyrogenetic capacity of the sample is 3 times that of embodiment 18, and thus the sample can be used in occasions where both light and thermal effects are required.

    [0051] Embodiment 61: NaGd.sub.0.9S.sub.2:Er.sub.0.1@NaGd.sub.0.78S.sub.2:Er.sub.0.18, Ho.sub.0.05

    [0052] Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaGd.sub.0.9S.sub.2:Er.sub.0.1 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaGd.sub.0.9S.sub.2:Er.sub.0.1 sample. Y.sub.2O.sub.3 (99.99%), Er.sub.2O.sub.3 (99.99%) and Ho.sub.2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.9S.sub.2: Er.sub.0.1 is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaGd.sub.0.9S.sub.2: Er.sub.0.1@NaGd.sub.0.78S.sub.2:Er.sub.0.18, Ho.sub.0.05 sample.

    [0053] FIG. 4 shows the emission spectrum of NaGd.sub.0.9S.sub.2:Er.sub.0.1@NaGd.sub.0.78S.sub.2:Er.sub.0.18, Ho.sub.0.05 sample under 980 nm laser excitation. The emission spectrum in FIG. 3 is formed by two groups of bands: 1) The red luminescence band located at band of 646-666 nm: there are three emission peaks, located at 650 nm, 654 nm and 661 nm respectively, corresponding to the .sup.5F.sub.5.fwdarw..sup.5I.sub.8 transition of Ho.sup.3+ ions. 2) The green luminescence band located at band of 535-565 nm: there are two emission peaks, located at 543 nm and 548 nm respectively, corresponding to the .sup.5F.sub.4.fwdarw..sup.5I.sub.8 and .sup.5S.sub.2.fwdarw..sup.5I.sub.8 transitions of Ho.sup.3+ ions.

    [0054] Embodiment 62: NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10@NaY.sub.0.89S.sub.2:Yb.sub.0.08, Nd.sub.0.01, Tm.sub.0.02

    [0055] Y.sub.2O.sub.3 (99.99%), Er.sub.2O.sub.3 (99.99%) and Nd2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10 sample. Y.sub.2O.sub.3 (99.99%), Yb.sub.2O.sub.3 (99.99%) and Tm.sub.2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10 is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10 @NaY.sub.0.89S.sub.2:Yb.sub.0.08, Nd.sub.0.01, Tm.sub.0.02 sample.

    [0056] FIG. 5 shows the emission spectrum of NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10@NaY.sub.0.89S.sub.2:Yb.sub.0.08, Nd.sub.0.01, Tm.sub.0.02 sample under 980 nm laser excitation. The spectrum in the figure is formed by three groups of bands: 1) The blue luminescence band located at band of 460-499 nm, and the peak value is located at 476 nm, which belongs to the .sup.1G4.fwdarw..sup.3H.sub.6 transition of Tm.sup.3+; 2) The red luminescence band located at band of 639-654 nm, and the peak value is located at 650 nm, which belongs to the .sup.1G4.fwdarw..sup.3F.sub.4 transition of Tm.sup.3+ ions ; and 3) the red luminescence band located at band of 670-726 nm, and the peak value is located at 698 nm, which belongs to the .sup.3F.sub.3.fwdarw..sup.3H.sub.6 transition of Tm.sup.3+ ions. The blue light emission band is significantly stronger than the two red light emission bands, so NaY.sub.0.8S.sub.2:Er.sub.0.10, Nd.sub.0.10@NaY.sub.0.89S.sub.2:Yb.sub.0.08, Nd.sub.0.01, Tm.sub.0.02 samples show bright blue luminescence under observation by naked eyes.

    [0057] Embodiment 63: NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Nd.sub.0.02

    [0058] Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaY.sub.0.9S.sub.2:Er.sub.0.10 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaY.sub.0.9S.sub.2:Er.sub.0.10sample. Y.sub.2O.sub.3 (99.99%), Yb.sub.2O.sub.3 (99.99%) and Nd.sub.2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.9S.sub.2:Er.sub.0.10is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Nd.sub.0.02 ample.

    [0059] The upconversion luminescence spectrum of the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Nd.sub.0.02 sample is formed by three groups of bands: green emission located at the band of 510-570 nm, red emission at the band of 640-700 nm and infrared emission at the band of 710-900 nm, corresponding to .sup.4S.sub.3/2.fwdarw..sup.4I.sub.15/2, .sup.2H.sub.11/2.fwdarw..sup.4I.sub.15/2 and .sup.4F.sub.9/2.fwdarw..sup.4I.sub.15/2 transitions of Er.sup.3+ ions and .sup.4F.sub.7/2/.sup.4F.sub.5/2/.sup.4F.sub.3/2.fwdarw..sup.4I.sub.9/2 transitions of Nd.sup.3+ ions, respectively. Compared with the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample, the pyrogenetic capacity of the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Nd.sub.0.02 sample is significantly improved.

    [0060] Embodiment 64: NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Sm.sub.0.02

    [0061] Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaY.sub.0.9S.sub.2:Er.sub.0.10 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaY.sub.0.9S.sub.2:Er.sub.0.10 sample. Y.sub.2O.sub.3 (99.99%), Yb.sub.2O.sub.3 (99.99%) and Sm2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.9S.sub.2:Er.sub.0.10 is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Sm.sub.0.02 sample.

    [0062] The upconversion luminescence spectrum of the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Sm.sub.0.02 sample is formed by three groups of bands: green emission located at the band of 550-580 nm and red emission at the bands of 580-630 nm and 630-675 nm, corresponding to .sup.4G5/2.fwdarw..sup.6H.sub.5/2, .sup.4G.sub.5/2.fwdarw..sup.6H.sub.7/2, .sup.4G.sub.5/2.fwdarw..sup.6H.sub.9/2 transitions of Sm.sup.3+ ions, respectively. Compared with the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample, the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Sm0.02 sample can generate much heat.

    [0063] Embodiment 65: NaY.sub.0.9S.sub.2:Er.sub.0.1@NaY.sub.0.9S.sub.2:Eu.sub.0.02

    [0064] Y.sub.2O.sub.3 (99.99%) and Er.sub.2O.sub.3 (99.99%) of a certain mass are weighed according to the stoichiometric ratio of NaY.sub.0.9S.sub.2:Er.sub.0.10 and stirred with appropriate amount of water and 6 mol/L hydrochloric acid to form rare earth chloride. An appropriate amount of oleic acid and octadecene are taken; and a certain amount of sulfur powder and sodium oleate are weighed, and mixed with the above rare earth chloride. The water and other low boiling point impurities are removed under vacuum environment at 120° C. Then, the solution is rapidly heated to 300° C. and kept at the temperature for 1 hour. The sample is washed with water and ethanol and dried for many times to obtain the NaY.sub.0.9S.sub.2:Er.sub.0.10 sample. Y.sub.2O.sub.3 (99.99%), Yb.sub.2O.sub.3 (99.99%) and Eu.sub.2O.sub.3 (99.99%) are weighed to prepare the rare earth chlorides. The above steps are repeated and the prepared NaY.sub.0.9S.sub.2:Er.sub.0.10 is added into the mixture and kept at 300° C. for 1 hour to form a core-shell structure NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Eu.sub.0.02 sample.

    [0065] The upconversion luminescence spectrum of the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Eu.sub.0.02 sample is formed by three groups of bands: green emission located at the band of 510-580 nm and red emission at the bands of 580-630 nm and 630-675 nm. Compared with the NaY.sub.0.9S.sub.2:Er.sub.0.1 sample, the red luminescence of the NaY.sub.0.9S.sub.2:Er.sub.0.10@NaY.sub.0.9S.sub.2:Yb.sub.0.08, Eu.sub.0.02 sample is significantly enhanced.

    [0066] Upconversion luminescence samples co-doped with Pr, Tb and the like can be obtained by using similar methods.

    [0067] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions that belong to the idea of the present invention are included within the protection scope of the present invention. It should be noted that for those ordinary skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered to be within the protection scope of the present invention.