Blue to UV Up-Converter Comprising Lanthanide Ions such as Pr3+ Activated Garnet and its Application for Surface Disinfection Purposes

Abstract

A garnet is doped with a lanthanide ion selected from praseodymium, gadolinium, erbium, and neodymium. For co-doping, at least two of the lanthanide ions are selected. The lanthanide ion doped garnet converts electromagnetic radiation energy of a longer wavelength of below 530 nm to electromagnetic radiation energy of shorter wavelengths in the range of 220 to 425 nm. The garnet is crystalline and is obtainable from a mixture of salts or oxides of the components, in the presence of a chelating agent, that are dissolved in acid. This is followed by a specific calcination process to produce the garnet and, optionally, to adjust particle size and increase the crystallinity of the particles. The garnet can be used to inactivate microorganisms or cells covering a surface containing silicate-based material under exposure of electromagnetic radiation energy of a longer wavelength of below 500 nm.

Claims

1: A garnet, doped with at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, neodymium, and, yttrium.

2: The garnet according to claim 1, wherein the garnet comprises lutetium on a position of a crystal lattice, wherein the position in the crystal lattice is doped with the at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, neodymium, and yttrium, or the garnet is a lutetium-aluminium garnet that is doped with the at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, and neodymium, or the garnet is a yttrium-aluminium garnet (YAG) that is doped with the at least one lanthanide selected from the group consisting of praseodymium, gadolinium, erbium, neodymium, and yttrium, or the garnet is a silicate garnet or an aluminium-silicate garnet that is doped with the at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, neodymium, and yttrium; wherein if the garnet is doped with more than one lanthanide ion, each lanthanide ion of the at least one lanthanide ion is different from another.

3: The garnet according to claim 1, wherein the at least one lanthanide ion is selected from the group consisting of praseodymium(III+), gadolinium(III+), erbium(III+), and neodymium(III+); and wherein if the garnet is doped with more than one lanthanide ion, the garnet is doped with a second lanthanide(III+) ion selected from the group consisting of praseodymium(III+), gadolinium(III+), erbium(III+), neodymium(III+), and yttrium(III+), wherein the second lanthanide(III+) ion is different from the at least one lanthanide ion.

4: The garnet according to claim 3, wherein the at least one lanthanide ion is praseodymium(III+), and wherein if the garnet is doped with more than one lanthanide ion, the garnet is doped with the second lanthanide(III+) ion.

5: The garnet according to claim 1, wherein the garnet converts electromagnetic radiation energy of a longer wavelength to electromagnetic radiation energy of a shorter wavelength.

6: The garnet according to claim 1, wherein the garnet is not a hydrate, and/or the garnet is free from hydroxyl-groups.

7: The garnet according to claim 1, wherein a crystallinity of the garnet is greater than 70%.

8: The garnet according to claim 1, wherein the garnet has the general formula I
Lu.sub.3-a-b-nLn.sub.b(Mg.sub.1-zCa.sub.z).sub.aLi.sub.n(Al.sub.1-u-vGa.sub.uSc.sub.v).sub.5-a-2n(Si.sub.1-d-eZr.sub.dHf.sub.e).sub.a+2nO.sub.12  I wherein a=0-1, 1≥b>0, d=0-1, e=0-1, n=0-1, z=0-1, u=0-1, v=0-1, with u+v≤1 and d+e≤1; and wherein Ln=praseodymium (Pr), gadolinium (Gd), erbium (Er) neodymium (Nd), or yttrium (Y).

9: The garnet according to claim 1, wherein the garnet has the general formula Ia
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-a-b-nLn.sub.b(Mg.sub.1-zCa.sub.z).sub.aLi.sub.n(Al.sub.1-u-vGa.sub.uSc.sub.v).sub.5-a-2n(Si.sub.1-d-eZr.sub.dHf.sub.e).sub.a+2nO.sub.12  Ia wherein a=0-1, 1≥b>0, d=0-1, e=0-1, n=0-1, x=0-1, y=0-1, z=0-1, u=0-1, v=0-1, with x+y=1, u+v≤1 and d+e≤1; wherein in formula Ia, Ln=praseodymium (Pr), erbium (Er), or neodymium (Nd).

10: The garnet according to claim 1, wherein the garnet has one of the following general formulas: formula Ib
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-bLn.sub.b(Al.sub.1-u-vGa.sub.uSc.sub.v).sub.5O.sub.12  Ib wherein in formula Ib, Ln.sub.b is Ln=Pr and b=0.001-0.05, x=0-1, y=0-1, u=0-1, v=0-1, formula Ic
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-b-aLn.sub.b(Mg.sub.1-zCa.sub.z).sub.a+bAl.sub.5-a-bSi.sub.a+bO.sub.12  Ic wherein in formula Ic, Ln.sub.b is Ln=Pr, 1≥b>0, a>0, x=0-1, y=0-1, z=0-1, formula Id
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.2-bLn.sub.b(Ca.sub.1-zMg.sub.z)Al.sub.4(Zr.sub.1-fHf.sub.r)O.sub.12  Id wherein in formula Id, Ln.sub.b is Ln=Pr, b>0, x=0-1, y=0-1, z=0-1, f=0-1, and formula Id*
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.1-bLn.sub.b(Ca.sub.1-zMg.sub.z).sub.2Al.sub.3(Zr.sub.1-fHf.sub.f).sub.2O.sub.12  Id* wherein in formula Id*, Ln.sub.b is Ln=Pr, 0.5≥b>0, x=0-1, y=0-1, z=0-1, f=0-1.

11: The garnet according to claim 1, wherein the garnet has one of the following general formulas:
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-bPr.sub.b(Al.sub.1-uGa.sub.u).sub.5-bO.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-bPr.sub.b(Al.sub.1-uSc.sub.v).sub.5-bO.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.3-bPr.sub.b(Ga.sub.1-uSc.sub.v).sub.5O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.2Pr.sub.bCaAl.sub.4SiO.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y)Pr.sub.bCa.sub.2Al.sub.3Si.sub.2O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.2Pr.sub.bMgAl.sub.4SiO.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y)Pr.sub.bMg.sub.2Al.sub.3Si.sub.2O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.2Pr.sub.bCaAl.sub.4(Zr.sub.dHf.sub.e)O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y)Pr.sub.bCa.sub.2Al.sub.3(Zr.sub.dHf.sub.e).sub.2O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y).sub.2Pr.sub.bMgAl.sub.4(Zr.sub.dHf.sub.e)O.sub.12,
(Lu.sub.1-x-yY.sub.xGd.sub.y)Pr.sub.bMg.sub.2Al.sub.3(Zr.sub.dHf.sub.e).sub.2O.sub.12, wherein b=0.001-0.05, u=0-1, v=0-1, x=0-1, y=0-1.

12: The garnet according to claim 1, wherein the garnet is a solid solution doped z with lanthanide ions comprising at least one earth alkali on and/or at least one alkali ion.

13: The garnet according to claim 1, wherein the garnet converts electromagnetic radiation energy of a longer wavelength of below 500 nm to electromagnetic radiation energy of shorter wavelengths in the range of 230 nm to 400 nm.

14: A process for the production of the garnet according to claim 1, the process comprising: dissolving the following components i), ii), v), and optionally, iii) and/or iv), in acid, i) at least one first lanthanide salt and/or lanthanide oxide, wherein a lanthanide ion in the at least one first lanthanide oxide and/or lanthanide salt is selected from the group consisting of praseodymium, gadolinium, erbium, neodymium, and a mixture thereof, ii) at least an element for a crystal garnet lattice selected from the group consisting of a) at least one second lanthanide salt or lanthanide oxide, b) an Si source, c) an aluminium source, and d) yttrium salt or yttrium oxide or a mixture thereof, iii) optionally, at least one earth alkali salt and/or earth alkali oxide, and/or iv) optionally, at least one alkali salt, and v) a chelating agent, evaporating the of acid and, optionally, the chelating agent at an elevated temperature, optionally under stirring, to obtain a concentrated reaction product, drying the concentrated reaction product by heating the concentrated reaction product above 100° C., to obtain a further product, heating up the further product to at least 600° C. for 1 to 10 h, to remove organic residues and to obtain a product with reduced organic content, heating the product with reduced organic content up to at least 1200° C. for 0.5 to 10 h, cooling down the product with reduced organic content, and obtaining the garnet.

15: The process according to claim 14, wherein at least one further salt and/or oxide is dissolved in the acid, wherein the at least one further salt and/or oxide is a scandium salt or scandium oxide, a gallium salt or gallium oxide, and/or a zirconium salt, zirconium oxide, hafnium salt, and/or hafnium oxide.

16: A garnet doped with the at least one lanthanide ion for converting electromagnetic radiation energy of a longer wavelength to electromagnetic radiation energy of shorter wavelength, obtainable according to the process of claim 14, wherein the game is doped with the at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, and neodymium, and wherein the garnet is one selected from the group consisting of a lutetium-aluminium garnet, a yttrium-aluminium garnet (YAG), a silicate garnet, and an aluminium-silicate garnet.

17: A garnet doped with the at least one lanthanide ion for converting electromagnetic radiation energy of a longer wavelength to electromagnetic radiation energy of shorter wavelength, obtainable according to the process of claim 14, wherein the garnet is doped with the at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, erbium, and neodymium, and wherein the garnet comprises above 95% of Ln.sup.3+ lanthanide ions and less than 5% of Ln.sup.4+ lanthanide ions, in respect to all Ln ions (sum up to 100%).

18: A composition, foil or film, comprising the garnet according to claim 1 for self-disinfection purposes or for reduction of microorganisms.

19: A method, comprising: adding the garnet according to claim 1 into a coating composition or a material to provide a coating or surface that is able to inactivate microorganisms or cells covering the coating or surface under exposure of electromagnetic radiation energy of a longer wavelength of below 500 nm.

20: The process according to claim 14, wherein the at least one first lanthanide salt and/or lanthanide oxide is selected from the group consisting of lanthanide nitrate, lanthanide carbonate, lanthanide carboxylate, lanthanide acetate, lanthanide sulphate, lanthanide oxide, and a mixture thereof; and/or wherein the at least one second lanthanide salt or lanthanide oxide is selected from the group consisting of lanthanide nitrate, lanthanide carbonate, lanthanide carboxylate, lanthanide acetate, lanthanide sulphate, lanthanide oxide, and a mixture thereof.

Description

EMBODIMENTS

Measurement Techniques

[0108] The X-ray diffractograms were recorded by using a Panalytical X'Pert PRO MPD diffractometer working in Bragg-Brentano geometry using Cu-Kα radiation and a line-scan CCD sensor. The integration time amounted to 20 s with a step size of 0.017°.

[0109] Emission spectra were recorded on an Edinburgh Instruments FLS920 spectrometer equipped with a 488 nm continuous-wave OBIS Laser by Coherent and a Peltier cooled (−20° C.) single-photon counting photomultiplier (Hamamatsu R2658P). Filters were used to suppress excitation by second order reflexes caused by the monochromators.

[0110] Emission spectra is excited with a laser, in particular a laser with an efficiency of 75 mW at 445 nm and/or an efficiency of 150 mW at 488 nm.

[0111] Milling is performed in a planetary ball mill (PM 200, Retsch), beaker/jar: corundum and grinding balls (Al.sub.2O.sub.3), 50 ml (9 balls, sample ca. 4.5 g) or 125 ml (24 balls, sample ca. 20 g) for 4 hours at 200 rotation/min after cooling of the final calcination step. Reducing atmosphere (H.sub.2/Inertgas, in particular H.sub.2/N.sub.2, preferred (H.sub.2 (5%)/N.sub.2 (95%)).

Powder Sample Synthesis

Comparative Example

[0112] As comparative example other lanthanide doped silicate systems disclosed in the below mentioned publication were produced and measured under same conditions (Visible-to-UVC up-conversion efficiency and mechanisms of Lu.sub.7O.sub.6F.sub.9:Pr.sup.3+ and Y.sub.2SiO.sub.5:Pr.sup.3+ ceramics, Cates, Ezra L.; Wilkinson, Angus P.; Kim, Jae-Hong, Journal of Luminescence 160 (2015) 202-209; Abstract: Visible-to-UVC up-conversion (UC) by Pr.sup.3+-doped materials is a promising candidate for application to sustainable disinfection technologies, including light-activated antimicrobial surfaces and solar water treatment. In this work, we studied Pr.sup.3+ up-conversion in an oxyfluoride host system for the first time, employing Lu.sub.7O.sub.6F.sub.9:Pr.sup.3+ ceramics. Compared to the previously studied Y.sub.2SiO.sub.5:Pr.sup.3+ reference material, the oxyfluoride host resulted in a 5-fold increase in intermediate state lifetime, likely due to a lower maximum phonon energy; however, only a 60% gain in UC intensity was observed. To explain this discrepancy, luminescence spectral distribution and decay kinetics were studied in both phosphor systems. The Pr.sup.3+4f5d band energy distribution in each phosphor was found to play a key role by allowing or disallowing the occurrence of a previously unexplored UC mechanism, which had a significant impact on overall efficiency.

[0113] Lu.sub.7O.sub.6F.sub.9:Pr.sup.3+: Could not be obtained under disclosed temperature and a synthesis under increased temperature and a pressure of 350 MPa was not able due to the availability of a temperable press.

[0114] Y.sub.2SiO.sub.5:Pr.sup.3+ was as synthesized according to the publication as a pure phase (Emission spectra see FIG. 1).

Powder Synthesis

Example 1: (Lu.SUB.0.99.Pr.SUB.0.01.).SUB.3.Al.SUB.5.O.SUB.12

[0115] 2.3637 g (5.9400 mmol) Lu.sub.2O.sub.3, 0.0204 g (0.0200 mmol) Pr.sub.6O.sub.11, 7.5027 g (20.0000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O and 7.7530 g (64.0000 mmol) tris(hydroxymethyl)aminomethane were dissolved in dilute nitric acid. After concentrating the mixtures by slow evaporation at 65° C. under vigorous stirring, the sol turned into a transparent, highly viscous gel. The temperature was subsequently raised to 300° C. to start the self-sustaining gel combustion process, which was accompanied by the development of a large amount of gas. The intermediate product was dried at 150° C. over night. To remove organic residues, the dried powder was calcined at 800° C. for four hours in air. A final calcination step at 1600° C. for four hours in air was carried out to obtain the product phase.

Example 2: (Lu.SUB.0.985.Pr.SUB.0.015.).SUB.2.CaAl.SUB.4.SiO.SUB.12

[0116] 1.5679 g (3.9400 mmol) Lu.sub.2O.sub.3, 0.0204 g (0.0200 mmol) Pr.sub.6O.sub.1, 0.4003 g (4.0000 mmol) CaCO.sub.3, 6.0021 g (16.0000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O, 0.8333 g (4.0000 mmol) Si(OC.sub.2H.sub.5).sub.4 and 15.6905 g (81.6680 mmol) citric acid were dissolved in dilute nitric acid. The solution was stirred vigorously at 65° C. to obtain a sol. The sol was dried at 150° C. over night to turn it into a gel. Subsequent calcination at 800° C. in a muffle furnace for four hours in air removed organic residues. A further calcination step at 1600° C. for four hours in air was performed to obtain the product phase.

Example 3: (Lu.SUB.0.99.Pr.SUB.0.01.).SUB.3.Ga.SUB.2.Al.SUB.3.O.SUB.12

[0117] 2.3637 g (5.9400 mmol) Lu.sub.2O.sub.3, 0.0204 g (0.0200 mmol) Pr.sub.6O.sub.1, 4.5016 g (12.0000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O, 3.7754 g (8.0000 mmol) Ga(NO.sub.3).sub.3.12H.sub.2O and 7.7530 g (64.0000 mmol) tris(hydroxymethyl)aminomethane were dissolved in dilute nitric acid. After concentrating the mixtures by slow evaporation at 65° C. under vigorous stirring, the sol turned into a transparent, highly viscous gel. The temperature was subsequently raised to 300° C. to start the self-sustaining gel combustion process, which was accompanied by the development of a large amount of gas. The intermediate product was dried at 150° C. over night. To remove organic residues, the dried powder was calcined at 800° C. for four hours in air. A final calcination step at 1600° C. for four hours in air was carried out to obtain the product phase.

Example 4: (Lu.SUB.0.99.Pr.SUB.0.01.).SUB.3.ScAl.SUB.4.O.SUB.12

[0118] 2.3637 g (5.9400 mmol) Lu.sub.2O.sub.3, 0.0204 g (0.0200 mmol) Pr.sub.6O.sub.1, 5.1374 g (16.0000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O and 15.6905 g (81.6680 mmol) citric acid were dissolved in dilute nitric acid. 0.5516 g (4.0000 mmol) Sc.sub.2O.sub.3 were dispersed in the aforementioned solution. The solution was stirred vigorously at 65° C. to obtain a sol. The sol was dried at 150° C. over night to turn it into a gel. Subsequent calcination at 800° C. in a muffle furnace for four hours in air removed organic residues. A further calcination step at 1600° C. for four hours in air was performed to obtain the product phase.

Example 5: (Lu.SUB.0.99.Pr.SUB.0.01.).SUB.2.LiAl.SUB.3.Si.SUB.2.O.SUB.12

[0119] 3.1516 g (7.9200 mmol) Lu.sub.2O.sub.3, 0.0272 g (0.0267 mmol) Pr.sub.6O.sub.11, 9.0032 g (24.0000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O, 0.2956 g (4.0000 mmol) Li.sub.2CO.sub.3, 3.3333 g (16.0000 mmol) Si(OC.sub.2H.sub.5).sub.4 and 40.3470 g (192.0000 mmol) citric acid were dissolved in dilute nitric acid. The solution was stirred vigorously at 65° C. to obtain a sol. The sol was dried at 150° C. over night to turn it into a gel. Subsequent calcination at 1000° C. in a muffle furnace for four hours in air removed organic residues. A further calcination step at 1600° C. for one hour in air was performed to obtain the product phase.

Example 6: (Lu.SUB.0.89.Pr.SUB.0.01.Gd.SUB.0.1.).SUB.2.Ca.SUB.2.Al.SUB.4.SiO.SUB.12

[0120] 1.4875 g (3.7380 mmol) Lu.sub.2O.sub.3, 0.1522 g (0.4200 mmol) Gd.sub.2O.sub.3, 0.9918 g (4.2000 mmol) Ca(NO.sub.3).sub.2.4H.sub.2O, 6.3022 g (16.8000 mmol) Al(NO.sub.3).sub.3.9H.sub.2O, 0.0365 g (0.0840 mmol) Pr(NO.sub.3).sub.3.6H.sub.2O, 0.8750 g (4.2000 mmol) Si(OC.sub.2H.sub.5).sub.4 and 21.1822 g (100.8000 mmol) citric acid were dissolved in dilute nitric acid. The solution was stirred vigorously at 65° C. to obtain a sol. The sol was dried at 150° C. over night to turn it into a gel. Subsequent calcination at 800° C. in a muffle furnace for four hours in air removed organic residues. A further calcination step at 1600° C. for four hours in air was performed to obtain the product phase.

Example 7: Ca.SUB.2.(Lu.SUB.0.99.Pr.SUB.0.01.)Sc.SUB.2.GaSi.SUB.2.O.SUB.12

[0121] 1.1819 g (2.9700 mmol) Lu.sub.2O.sub.3, 0.8275 g (6.0000 mmol) Sc.sub.2O.sub.3, 0.0083 g (0.0082 mmol) Pr.sub.6O.sub.11, 1.2010 g (12.0000 mmol) CaCO.sub.3, 2.5000 g (12.0000 mmol) Si(OC.sub.2H.sub.5).sub.4 and 30.2602 g (144.0000 mmol) citric acid were dissolved in dilute nitric acid. The solution was stirred vigorously at 65° C. to obtain a sol. The sol was dried at 150° C. over night to turn it into a gel. Subsequent calcination at 1000° C. in a muffle furnace for four hours in air removed organic residues. A further calcination step at 1400° C. for one hour in air was performed to obtain the product phase.

DESCRIPTION OF FIGURES

[0122] FIG. 1: Emission spectrum of Y.sub.2SiO.sub.5:Pr.sup.3+ upon excitation at 445 nm and 488 nm.

[0123] FIG. 2: X-ray diffraction pattern of (Lu.sub.0.99Pr.sub.0.01).sub.3Al.sub.5O.sub.12 for Cu—K.sub.α radiation (Example 1).

[0124] FIG. 3: X-ray diffraction pattern of (Lu.sub.0.985Pr.sub.0.015).sub.2CaAl.sub.4SiO.sub.12 for Cu—K.sub.α radiation (Example 2).

[0125] FIG. 4: X-ray diffraction pattern of (Lu.sub.0.99Pr.sub.0.01).sub.3Ga.sub.2Al.sub.3O.sub.12 for Cu—K.sub.α radiation (Example 3).

[0126] FIG. 5: X-ray diffraction pattern of (Lu.sub.0.99Pr.sub.0.01).sub.3ScAl.sub.4O.sub.12 for Cu—K.sub.α radiation (Example 4).

[0127] FIG. 6: X-ray diffraction pattern of (Lu.sub.0.99Pr.sub.0.01).sub.2LiAl.sub.3Si.sub.2O.sub.12 for Cu—K.sub.α radiation (Example 5).

[0128] FIG. 7: Emission spectrum of (Lu.sub.0.99Pr.sub.0.01).sub.3Al.sub.5O.sub.12 upon excitation at 488 nm (Example 1).

[0129] FIG. 8: Emission spectrum of (Lu.sub.0.985Pr.sub.0.015).sub.2CaAl.sub.4SiO.sub.12 upon excitation at 445 nm (Example 2).

[0130] FIG. 9: Emission spectrum of (Lu.sub.0.99Pr.sub.0.01).sub.3Ga.sub.2Al.sub.3O.sub.12 upon excitation at 488 nm (Example 3).

[0131] FIG. 10: Emission spectrum of (Lu.sub.0.99Pr.sub.0.01).sub.3ScAl.sub.4O.sub.12 upon excitation at 445 nm (Example 4).

[0132] FIG. 11: Emission spectrum of (Lu.sub.0.99Pr.sub.0.01).sub.2LiAl.sub.3Si.sub.2O.sub.12 upon excitation at 488 nm (Example 5).

[0133] FIG. 12: Emission spectrum of (Lu.sub.0.99Pr.sub.0.01).sub.3Al.sub.5O.sub.12 and the germicidal action curve for E. coli (DIN 5031-10).

[0134] FIG. 13: Emission spectrum of (Lu.sub.0.985Pr.sub.0.015).sub.2CaAl.sub.4SiO.sub.12 and germicidal action curve for E. coli (DIN 5031-10).

[0135] FIG. 14a: X-ray diffraction pattern of (Lu.sub.0.89Pr.sub.0.01Gd.sub.0.1).sub.2Ca.sub.2Al.sub.4SiO.sub.12 for Cu—K.sub.α radiation (Example 6).

[0136] FIG. 14b: Emission spectrum of (Lu.sub.0.89Pr.sub.0.01Gd.sub.0.1).sub.2Ca.sub.2Al.sub.4SiO.sub.12 upon excitation at 445 nm (Example 6).

[0137] FIG. 15a: X-ray diffraction pattern of Ca.sub.2(Lu.sub.0.99Pr.sub.0.01)Sc.sub.2GaSi.sub.2O.sub.12 for Cu—K.sub.α radiation (Example 7).

[0138] FIG. 15b: Emission spectrum of Ca.sub.2(Lu.sub.0.99Pr.sub.0.01)Sc.sub.2GaSi.sub.2O.sub.12 upon excitation at 445 nm (Example 7). The garnet possesses a range of emission from 280 to 400 nm with a maximum at 310 nm.