BACKGROUND

Field

[0001] These embodiments relate to a silicon oxynitride phosphor composition that provides green or orange light, a phosphor element, or a phosphor converted Light Emitting Diode (pc-LED) lighting device comprising the phosphor composition.

Description of the Related Art

[0002] Light Emitting Diode (LED) based lighting has been attractive technology for future lighting development due to LED longer operational lives in comparison to incandescent lamps. In addition, energy efficiency has also become an important criterion for lighting products. This has contributed the demand to replace traditional light sources like light bulbs with LED light sources because LED light sources tend to be more efficient. For white-light applications, a preferred light source is a blue LED driving white-light luminescence. However, over thousands of years, people have developed a preference towards warm white for indoor lighting instead of cool colors. As a result, there is a need for phosphors activated by blue LEDs which will result in the generation of warm-white lighting.

[0003] As a result, development of new photo luminescent materials has become a topic of great interest. The current state of the art in solid-state chemistry is to design new photo luminescent materials with good properties in terms of thermal and chemical stability, toxicity and luminosity. Despite advances, there is still a need for developing phosphors to provide increased options for pc-LEDs with optimized quantum efficiency and color rendering.

SUMMARY

[0004] New phosphor materials have been successfully synthesized by solid state reaction which addresses the need for new phosphor materials. The new silicon oxynitride phosphor materials emit either orange or green light depending upon which dopants are introduced into the phosphor. These phosphor elements can be used in conjunction with LEDs to provide increased lighting options for pc- LEDs. [0005] Some embodiments include a phosphor composition comprising a compound defined by the formula:

Μ _α Μΐ ί ₉ _ _α Ν _Ί _,0, : Ε _χ ;

wherein 0 < a < 3; 0 < b < 6; 0.03 < x < 0.9; M ¹ comprises Li, K, Na, or a combination thereof; M" can comprise Ba, Ca, Mg, Sr, Zn, or a combination thereof; and RE comprises Ce, Pr, Sm, Eu, Tb, or a combination thereof (Si is silicon; N is nitrogen; O is oxygen).

[0006] In some embodiments, the composition can comprise: (Lii . ₈ Nao.2)Ca ₆ Si8.5Ni ₄ 03: Eu ²⁺ , Li ₂ Ca ₆ Si8. ₅ Ni ₄ 0 ₃ :Ce ³⁺ , Li ₂ Ca ₆ Si8.5Ni ₄ 0 ₃ : Eu ²⁺ , and/or combinations thereof. I n some embodiments, the composition can comprise the compound Li ₂ Ca ₆ Si8.5N ₁₄ 0 ₃ : Eu ²⁺ . In some embodiments, the phosphor composition can comprise: Li ₂ Ca _{5 4} Euo.6Si8.5 i ₄ 0 ₃ , Li ₂ Ca _{5 7} Euo. ₃ Si8.5Ni ₄ 0 ₃ ,

Li ₂ Ca5 88Euo.i2Si8.5 i ₄ 0 ₃ , Li ₂ Cas g ₄ Euo.o6Si8.5N i ₄ 0 ₃ , (Li i .8Na ₀ . ₂ )Ca5 88Euo.i ₂ Si8.5 i ₄ 0 ₃ , Li ₂ Ca ₅ .88Ceo.i ₂ Si8.5N ₁₄ 0 ₃ , and/or combinations thereof. In some embodiments, the phosphor composition can comprise the compound Li ₂ Ca ₅ .88Euo.i ₂ Si8.5N ₁₄ 0 ₃ .

[0007] Some embodiments include a phosphor element comprising a phosphor composition described herein. In some embodiments, a phosphor element described herein further comprises a sintering aid. I n some embodiments, the sintering aid can comprise MgO and/or CaO.

[0008] In some embodiments, the phosphor element can have at least about 70 T _t % for all light in the wavelength ranging from to about 31 0 nm to about 500 nm. In some embodiments, the phosphor element can have an emissive peak wavelength between about 495-620 nm. In some embodiments, the phosphor element can have an emissive peak wavelength between about 495-570 nm. In some embodiments, the phosphor element can have an emissive peak wavelength between about 590-620 nm.

[0009] Some embodiments include a lighting device comprising a phosphor element described herein and an LED, wherein the element can be applied directly upon the LED. In some embodiments, the LED can be a blue LED. In some embodiments, the phosphor element can emit orange light. In some embodiments, the phosphor element can emit green light. In some embodiments, as a result of the combined emission of the LED and the phosphor, the lighting device can provide a soft white light.

[0010] These and other embodiments are described in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a depiction of the unit cell of the CaSiNO crystal or Li ₂ Ca ₆ Si8.5N ₁₄ 0 ₃ . In the figure, the Li atoms are not shown for clarity and the oxide and nitride atoms occupy the same sites.

[0012] Fig. 2 is a close up depiction within the cell of the surrounding area around the Ca-lons.

[0013] Fig. 3 is an elevation view of an embodiment of a lighting device described herein containing the phosphor element.

[0014] Fig. 4 is a plot of measured X-ray diffraction patterns measured against the theoretical pattern for CaSiNO validating synthesis.

[0015] Fig. 5 is a Scanning Electron Microscope image of CaSiNO showing the formation of the unit crystals.

[0016] Fig. 6 are the Excitation/Emission spectra for Li ₂ Ca ₆ Si8.5N ₁₄ 0 ₃ :Eu ²⁺ .

[0017] Fig. 7 is a picture showing the blue to green shift with increasing concentrations of Eu-dopant.

[0018] Fig. 8 is a plot showing internal quantum efficiency, absorption, and external quantum efficiency for a lighting device embodiment using phosphor element PC-2.

DETAILED DESCRIPTION

[0019] Some LED light sources use an ln _1-x Ga _x N-chip to generate blue light which is converted into white light afterwards. Some converter materials involve for example YAG:Ce ³⁺ as yellow emitter and (Ca,Sr)SiAIN ₃ :Eu ²⁺ , (Ca,Sr) ₂ Si ₅ N ₈ or Sr[LiAI ₃ N ₄ ]:Eu ²⁺ as red emitter. YAG:Ce possesses good properties in terms of chemical and thermal stability or the efficient absorption of blue light which are essential requirements for such materials. An additive color mixing of these emitters allow the generation of warm white light. However, increasing performance demands and limited availability of existing materials highlight a need for more compounds with properties that lend themselves as suitable phosphors.

[0020] Another very interesting family of compounds is oxonitridosilicates with prominent examples like Ca ₃ Si ₂ 0 ₄ N ₂ : Eu ²⁺ as green emitter, Sr ₂ SiN _z 0 ₄ -i. _5z :Eu ²⁺ as red emitter and Sro.25Bao. 5Si ₂ 0 ₂ N ₂ : Eu ²⁺ for the emission of blue light. These oxonitridosilicate materials show very good properties in terms of thermal and chemical resistance and quantum efficiency. Another example of a phosphor is SrSi ₂ 0 ₂ N ₂ with Eu ²⁺ doping that provides broad emission at 200 °C for wavelengths up to 530 nm.

[0021 ] Some embodiments include a silicon oxynitride phosphor composition and associated phosphor elements and lighting devices based on these compositions. In some embodiments, the phosphor element can comprise one or more phosphor compositions. In some embodiments, the phosphor composition comprises a compound represented by the following formula:

M _4a M xSi9-aNi _7-b O _b : RE _X ; (Formula 1 )

where a can be greater than 0 and less than or equal to 3, b can be greater than 0 and less than or equal to 6; where M ¹ can comprise Li, Na, K, or a mixture thereof; M" can comprise Ba, Ca, Mg, Sr, Zn, or a mixture thereof; RE can be a rare earth dopant that can comprise: Ce, Pr, Sm, Eu, Tb, or a mixture thereof; and x is the dopant amount.

[0022] In some embodiments, the phosphor composition can be comprised of a compound represented by the following formula: : RE _X ; (Formula 2)

where a can be greater than 0 and less than or equal to 0.5, b can be greater than 0 and less than or equal to 6; where M ¹ can comprise Li, Na, or a mixture thereof; (Ca is calcium); RE can be a rare earth dopant that can comprise: Ce, Eu, or a mixture thereof; and x is the dopant amount. [0023] In some embodiments, a is 0.01 -0.1 , 0.1 -0.3, 0.2-0.4, 0.3-0.5, 0.4- 0.6, about 0.5, 0.5-0.7, 0.6-0.8, 0.7-0.9, 0.8-1 , 1 -2, 2-3 or any number in a range bounded by any of these values.

[0024] In some embodiments, b is 0.1 -1 , 1 -2, 2-2.3, 2.2-2.5, 2.4-2.7, 2.6- 2.9, 2.9-3.1 , 3-3.3, about 3, 3.2-3.5, 3.4-3.7, 3.6-4, 4-5, 5-6, or any number in a range bounded by any of these values.

[0025] In some embodiments, x is 0.03-0.6, about 0.06, 0.04-0.07, 0.05- 0.08, 0.06-0.09, 0.08-0.12, 0.09-0.13, 0.1 -0.14, 0.12-0.17, about 0.12, 0.16-0.2, 0.2- 2.5, 0.22-0.27, 0.25-0.28, 0.27-0.31 , 0.28-0.32, 0.3-0.35, about 0.3, 0.32-0.4, 0.35- 0.45, 0.4-0.5, 0.55-0.65, 0.58-0.63, 0.5-0.7, 0.58-0.62, 0.5-0.8, 0.6-0.9, about 0.6, 0.7-0.8, 0.8-0.9, or any number in a range bounded by any of these values.

[0026] In some embodiments, the phosphor composition can comprise: (Lii.8Nao.2)Ca ₆ -xSi8.5Ni ₄ 0 ₃ :Eu ²⁺ _x , Li ₂ Ca6-xSi8.5Ni ₄ 0 ₃ :Ce ³⁺ x, Li ₂ Ca6-xSi8.5Ni ₄ 0 ₃ :Eu ²⁺ x, and/or combinations thereof. In some embodiments, the phosphor composition can comprise the compound Li ₂ Ca ₆ -xSi8.5N ₁₄ 0 ₃ :Eu ²⁺ x. In some embodiments, the phosphor composition can comprise of material based on the unit cell of Li ₂ Ca ₆ Si8.5N ₁₄ 0 ₃ , shown in Figure 1 . in some embodiments, a calcium atom is surrounded by nitrogen atoms as shown in Figure 2.

[0027] In some embodiments, the dopant amount, x, can be any value from about 0.03 to about 0.9 so that the rare earth dopant (e.g. Eu, Ce, and the like) can have a relative atomic ratio of between about 0.5 at% to about 15 at% with respect to the element being substituted (e.g. calcium). The relative atomic ratio is defined as the atomic ratio of the dopant to the pre-doped amount of the substituted element. For example, if Europium is being doped in place of Calcium at a relative atomic ratio of 10 at% and Calcium with has 6 atoms per molecule; the resulting molar ratios are Eu of 0.6 and Ca of 5.4 respectively. In some embodiments, the dopant amount is chosen such that the relative atomic ratio of the rare earth dopant and the substituted element can be between about 0.05 at%, about 0.1 at%, about 0.5 at%, about 1 .0 at%, about 1 .5 at%, about 2 at%, about 3.5 at%, about 4 at%, about 5 at%, about 7.5 at%, to about 10 at%, or any range combination of the above ratios. In some embodiments, the rare earth dopant may be doped at a relative atomic ratio of about 1 at% to about 10 at% (or x equal to about 0.06 to about 0.6). In some embodiments, the phosphor composition can comprise: Li ₂ Ca5. ₄ Euo.6Si8.5Ni ₄ 0 ₃ (doping of 10 at% Eu), Li ₂ Ca5. ₇ Euo.3Si8.5 i ₄ 0 ₃ (doping of 5 at% Eu), Li ₂ Ca5.88Euo.i2Si8.5 i ₄ 0 ₃ (doping of 2 at% Eu), L^Cas sMEuo oeSis s uC (doping of 1 at% Eu), (Lii.8Nao.2)Ca5.88Euo.i2Si8.5Ni ₄ 03 (doping of 2 at% Eu), Li ₂ Ca5.88Ceo.i2Si8.5N ₁₄ 0 ₃ (doping of 2 at% Ce), and/or combinations thereof. In some embodiments, as a result of doping, the phosphor composition can comprise the compound Li ₂ Ca5.88Euo.i2Si8.5N ₁₄ 0 ₃ (doping of 2 at% Eu).

[0028] In some embodiments, phosphor composition can have an emissive peak wavelength between about 495 nm to about 620 nm. In some embodiments, the phosphor composition can have a green emissive peak, or an emissive peak wavelength between about 495 nm to about 570 nm. In other embodiments, the phosphor composition can have an orange emissive peak, or an emissive peak wavelength between about 590 nm to about 620 nm.

[0029] In some embodiments, the phosphor element comprises one or more phosphor compositions described herein. In some embodiments, the phosphor element can have an emissive peak wavelength between about 495 nm to about 620 nm. In some embodiments, the phosphor element can have a green emissive peak, or an emissive peak wavelength between about 495 nm to about 570 nm. In other embodiments, the phosphor element can have an orange emissive peak, or an emissive peak wavelength between about 590 nm to about 620 nm.

[0030] In some embodiments, the phosphor element can be characterized as having a transmittance of at least 50 T _t %, at least 60 T _t %, at least 70 T _t %, at least 80 T _t %, at least 85 T _t % for all light in the wavelength range of between about 310 nm to about 500 nm, where T _t % refers to the percentage of radiation passing through the material as compared to the original amount of radiation impinging upon the material. In some embodiments, the phosphor element can have a transmittance of at least 70 T _t % for all light in the wavelength range of between about 310 nm to about 500 nm. A suitable method for determining visible light transparency is disclosed in United States Patent 8, 169, 136, which is incorporated by reference for its disclosure of determining total light transmission percentage.

[0031] In some embodiments, the phosphor element can further comprise a sintering aid. In some embodiments, the sintering aid can comprise: silicates such as but not limited to: Zr or Mg or Ca silicates, tetraethoxysilane (TEOS), colloidal silica, silicon dioxide, and mixtures thereof; oxides and fluorides such as but not limited to lithium oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, strontium oxide, boron oxide, calcium fluoride, and mixtures thereof. In some embodiments, the sintering aid can comprise of at least magnesium oxide and/or calcium oxide. In some embodiments, the mass ratio of the sintering aid can vary from about 0.01 wt% to about 5 wt%.

[0032] In some embodiments, the phosphor element can also comprise dispersants such as ammonium salts, e.g., NH ₄ CI; Flowlen; fish oil; long chain polymers; steric acid; oxidized Menhaden Fish Oil (MFO); dicarboxylic acids such as but not limited to succinic acid, ethanedioic acid, propanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, o-phthalic acid, and p-phthalic acid; sorbitan monooleate; and mixtures thereof. Some embodiments preferably use oxidized MFO as a dispersant.

[0033] In some embodiments, the phosphor element can also comprise plasticizers, which include type 1 plasticizers that can generally decrease the glass transition temperature (Tg), e.g. makes it more flexible, phthalates (n-butyl, dibutyl, dioctyl, butyl benzyl, missed esters, and dimethyl); and type 2 plasticizers that can enable more flexible, more deformable layers, and perhaps reduce the amount of voids resulting from lamination, e.g., glycols (polyethylene; polyalkylene; polypropylene; triethylene; dipropylglycol benzoate).

[0034] Type 1 plasticizers can include, but are not limited to butyl benzyl phthalate, dicarboxylic/tricarboxylic ester-based plasticizers such as but not limited to phthalate-based plasticizers such as but not limited to bis(2-ethylhexyl) phthalate, diisononyl phthalate, bis(n-butyl)phthalate, butyl benzyl phthalate, diisodecyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, diethyl phthalate, diisobutyl phthalate, di-n-hexyl phthalate and mixtures thereof; adipate-based plasticizers such as but not limited to bis(2-ethylhexyl)adipate, dimethyl adipate, monomethyl adipate, dioctyl adipate and mixtures thereof; sebacate-based plasticizers such as but not limited to dibutyl sebacate, and maleate.

[0035] Type 2 plasticizers can include, but not limited to dibutyl maleate, diisobutyl maleate and mixtures thereof, polyalkylene glycols such as but not limited to polyethylene glycol, polypropylene glycol and mixtures thereof. Other plasticizers which may be used include but are not limited to benzoates, epoxidized vegetable oils, sulfonamides such as but not limited to N-ethyl toluene sulfonamide, N-(2- hydroxypropyl)benzene sulfonamide, N-(n-butyl)benzene sulfonamide, organophosphates such as but not limited to tricresyl phosphate, tributyl phosphate, glycols/polyethers such as but not limited to triethylene glycol dihexanoate, tetraethylene glycol diheptanoate and mixtures thereof; alkyl citrates such as but not limited to triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, trioctyl citrate, acetyl trioctyl citrate, trihexyl citrate, acetyl trihexyl citrate, butyryl trihexyl citrate, trimethyl citrate, alkyl sulphonic acid phenyl ester and mixtures thereof.

[0036] In some embodiments, the phosphor element can also comprise binders. In some embodiments, organic binders can be used. In some embodiments, the organic binders used can comprise vinyl polymers such as but not limited to polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), polyvinyl acetate (PVAc), polyacrylonitrile, mixtures thereof and copolymers thereof; polyethyleneimine; poly methyl methacrylate (PMMA); vinyl chloride-acetate; and mixtures thereof. In some embodiments, PVB can be used as an organic binder.

[0037] In some embodiments, the phosphor element be synthesized using a solvent. In some embodiments, the solvent can comprise a polar solvent. In some embodiments, the polar solvent can comprise water. In some embodiments, the solvent can comprise a non-polar solvent. In some embodiments, the non-polar solvent can be an organic solvent. In some embodiments, the non-polar solvent can include, but is not limited to, a lower alkanol such as but not limited to ethanol, methanol, isopropyl alcohol, xylenes, cyclohexanone, acetone, toluene and methyl ethyl ketone, and mixtures thereof. In some embodiments, the non-polar solvent can be toluene.

[0038] The phosphor element may be prepared using conventional techniques known by a person skilled in the art. As an example, the phosphor element compositions may be produced using known solid state reaction processes for the production of phosphors by combining, for example, elemental oxides, nitrides, halides, oxonitrides, and/or oxohalides as starting materials. The starting material, or precursors, may be mixed together by any mechanical method including, but not limited to, stirring or blending in a high-speed blender or a ribbon blender. Alternatively the starting material may be combined and subjected to comminution in a bowl mill, a hammer mill, jet mill, ball mill, or manually in an agate mortar with a pestle. The firing may be conducted in a batch-wise or continuous process. The mixture may be fired in inert gas atmosphere at a temperature from about 800 °C to about 1400 °C. Typically a firing time up to 48 hours is adequate. Reaction temperatures and the dwell hours may be reduced drastically by the employment of nanopowder starting material. Alternatively, a crucible containing the precursors, for example a sealed Niobium ampoule (inert gas atmosphere), may be packed in a second closed crucible, for example a evacuated Si0 ₂ ampoule, and fired in air up to a maximum of 1200 °C. The result is a phosphor composition that can be deposited onto a substrate or LED via conventional techniques known by a person skilled in the art such as but not limited to: chemical vapor deposition, physical vapor deposition, and/or tape casting. Additionally, as is common in the state of the art, precursors can be also transformed in their final shape by forming the precursors in their final form before firing.

[0039] As seen in Figure 3, some embodiments include a lighting device, 100. The lighting device can comprise a phosphor element, 120, and a light emitting diode (LED) device, 110, the LED in optical communication with the phosphor element. In some embodiments, the phosphor element can comprise the phosphor composition of Formula 1 . In some embodiments, the electrical current can be provided by the conducting wires, 140, through the conductive base, 150, to the LED, all in electrical communication with each other, to emit light. In some embodiments, the LED, 110, can emit primary light which excites the phosphor in the ceramic element, 120, to generate complementary light which combines with the primary light before exiting the encapsulating resin, 130. In some embodiments, the primary and complementary light can combine to emit white light corresponding to a color temperature of about 2500 K to about 3000 K (e.g. about 2700 K) or soft white. In some embodiments, the phosphor ceramic element, 120, can be applied as a plate covering the LED as opposed to the phosphor being suspended as particles above the LED within the encapsulating resin, 310. [0040] In some embodiments, the LED can output light with the peak intensity from about 430 nm to about 470 nm. In some embodiments, the LED, 110, can be a blue LED with a peak wavelength of 450 nm. In some embodiments, the blue LED can be in optical communication with the phosphor element 120. In some embodiments, the phosphor element, 120, can emit an orange light when blue light emitted by the blue LED impinges upon the phosphor element. In other embodiments, the phosphor element, 120, emits a green light when blue light emitted by the blue LED impinges upon the phosphor element. In some embodiments, the lighting device, 100, can provide soft-white light as the result of the complimentary emissions of the blue LED and the phosphor's emitted light.

EXAMPLES

[0041] It has been discovered that embodiments of the silicon oxynitride phosphor composition and related elements and devices described herein provide the ability to generate green or orange light which improves the ability to provide soft white light with pc-LED based lighting devices. These benefits are further shown by the following examples, which are intended to be illustrative of the embodiments of the disclosure, but are not intended to limit the scope or underlying principles in any way.

Example 1 : Non-doped Crystal Formation

[0042] In example 1 , the preparation of the precursors for the synthesis of Li ₂ Ca ₆ Si8.5N ₁₄ 0 ₃ was performed in an argon atmosphere inside a glove-box. 66.6 mg Si ₃ N ₄ (Sigma Aldrich, St. Louis, MO, USA, nanopowder, < 50 nm, > 98.5 % trace metals basis), 135.5 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 33.0 mg Li ₃ N (Alfa Aesar, Ward Hill, MA, USA, 99.4 % metal basis) and with 18.3 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor compound, PC-1 .

Example 2: 2 at% Eu-doped Crystal Phosphor Formation

[0043] In Example 2, the preparation of the reaction mixture for the synthesis of Li2Ca5.88Si8.5NuO3Euo.12 was performed in an argon atmosphere inside a glove-box. 65.4 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 130.4 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 32.5 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 18.0 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) and with 5.3 mg EuCI ₂ (Aldrich, > 99.99 % trace metal basis) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-2.

Example 3: Na/Li Mixture and 2 at% Eu-doped Phosphor Formation

[0044] In Example 3, the preparation of the reaction mixture for the synthesis of Li1.8Nao.2Ca5.88Si8.5NuO3Euo.12 was performed in an argon atmosphere inside a glove-box. 65.1 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 129.9 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 32.3 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 17.9 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 5.3 mg EuCI ₂ (Aldrich, > 99.99 % trace metal basis), and 2.3 mg NaCI (Merck, Billerica, MA, USA, p.A.) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-3.

Example 4: 2 at% Ce-doped Phosphor Formation

[0045] In Example 4, the preparation of the reaction mixture for the synthesis of Li2Ca5.88Si8.5NuO3Ceo.12 was performed in an argon atmosphere inside a glove-box. 65.5 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 130.7 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 32.5 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 18.0 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) and with 5.9 mg CeCI ₃ (Alfa Aesar, > 99.9 % REO) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-4.

Example 5: 1 at% Eu-doped Phosphor Formation

[0046] In Example 5, the preparation of the reaction mixture for the synthesis of Li2Ca5.swSi8.5NuO3Euo.06 was performed in an argon atmosphere inside a glove-box. 66.0 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 132.9 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 32.8 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 18.1 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) and with 2.7 mg EuCI ₂ (Aldrich, > 99.99 % trace metal basis) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-5. Example 6: 5 at% Eu-doped Phosphor Formation

[0047] In Example 6, the preparation of the reaction mixture for the synthesis of Li ₂ Ca5 _.7 Euo. ₃ Si8.5N ₁₄ 0 ₃ was performed in an argon atmosphere inside a glove-box. 63.7 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 123.1 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 31 .6 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 17.5 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) and with 13.0 mg EuCI ₂ (Aldrich, > 99.99 % trace metal basis) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-6.

Example 7: 10 at% Eu-doped Phosphor Formation

[0048] In Example 7, the preparation of the reaction mixture for the synthesis of Li ₂ Ca ₅ . ₄ Si8.5N ₁₄ 0 ₃ Euo.6 was performed in an argon atmosphere inside a glove-box. 61 .0 mg Si ₃ N ₄ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis), 1 1 1 .8 mg CaCI ₂ (Aldrich, > 99.99 % trace metal basis), 30.3 mg Li ₃ N (Alfa Aesar, 99.4 % metal basis), 16.8 mg Si0 ₂ (Aldrich, nanopowder, < 50 nm, >98.5 % trace metals basis) and with 24.9 mg EuCI ₂ (Aldrich, > 99.99 % trace metal basis) were ground in an agate mortar until the mixture was thoroughly mixed. The result was a precursor mixture. The reaction was carried out in a fused niobium ampoule which was sealed into a silica ampoule. The precursor mixture was placed into the assembly inside the fused niobium ampoule and then heated to 1 100 °C with a heating rate of about 2 °C per minute, held at this temperature for 24 hours and cooled down to room temperature at a rate of about 2 °C per minute. The ampoules were opened in air, washed twice with deionized water and acetone. The resulting runoff was then dried in air to extract phosphor composition, PC-7. Example 8: X-Rav Diffraction

[0049] In Example 8, the compositions were inspected by X-ray powder diffraction (XRD), recorded with a Stadi-P (STOE, Darmstadt) powder diffractometer, using germanium monochromated Cu-K^ radiation, and a Mythen 1 K detector to verify their composition. The XRD plot against a simulated theoretical pattern for PC- 2 is shown in Figure 4. In addition, a TEM image of Li ₂ Ca ₆ Si8.5N ₁₄ 03, PC-1 , is also shown in Figure 5 showing the formation of unit cells.

Example 9: Optical Measurements

[0050] In Example 9, the optical characteristics of a lighting element created by PC-2 were characterized. In addition, the compositions identified in Examples 1 , 3, 4, 5, 6, and 7 can also be examined to determine their optical characteristics (i.e. PC-1 , PC-2 thru PC-7).

[0051] The transmittance of the identified phosphors was measured by a high sensitivity multi channel photo detector (MCPD 7000, Otsuka Electronics Co., Ltd., Osaka, JP). First, a glass plate was irradiated with continuous spectrum light from a halogen lamp source (150 W, MC2563, Otsuka Electronics Co., Ltd.) to obtain reference transmission data. Next, each phosphor was placed on the reference glass and irradiated. The transmission spectrum was acquired by the photo detector (MCPD) for each sample. In this measurement, each phosphor plate on the glass plate was coated with paraffin oil having the same refractive index as the glass plate. Transmittance at 800 nm wavelength of light was used as a quantitative measure of transparency of the phosphor ceramic plates.

[0052] Next for the identified samples, each was then mounted onto a blue LED chip (Cree [Durham, N.C., USA] blue-LED chip, dominant wavelength 455[452] nm, C455EZ1000-S2001 ) and the LED was operated at DC 100 mA at 2.9 V to excite the samples. Total light transmittance data for the samples was measured for each sample by using the measurement system as described in U.S. Patent Publication No. 2009-0212697, published August 27, 2099, Ser. No. 12/389,207, filed February 19, 2009 (MCPD 7000, Otsuka Electronics, Inc, Xe lamp, monochromator, and integrating sphere equipped). Photoluminescent spectrum of the samples excited by a blue light (the peak wavelength was 460 nm) from monochromator was also acquired by using same photo detector.

[0053] In addition, the excitation of PC-2 was characterized for different emission wavelengths by varying the LED wavelength; see Figure 6. When the input wavelength was varied, it was found that the excitation spectra of the compound at the desired output wavelength of 530 nm exhibited a maximum excitation at around 405 nm, as shown by the excitation spectrum in Figure 6. This behavior is also seen by a relative comparison of three emission spectra of PC-2 at input wavelengths of 360 nm, at 405 nm, and at 460 nm. The emission of PC-2 at an LED wavelength of 405 nm produced the greatest emissions.

[0054] The luminescence efficiency of PC-2 was also measured under various temperatures to determine the thermal effect on the phosphor. The findings for internal quantum efficiency (IQE), absorption (Abs.), and external quantum efficiency (EQE) as a function of temperature are presented in Figure 8.

[0055] The luminescence efficiency of phosphor powder was evaluated by measuring the emission from the phosphor powders irradiated by standard excitation light with a predetermined intensity. The IQE of a phosphor is the ratio of the number of photons generated from the phosphor to the number of photons of excitation light which penetrate into the phosphor.

[0056] The IQE, EQE and Abs. of a phosphor material can be expressed by the following formulae:

InternalQuantumEfficiency

ExternalQuantumEfficiency(X) = InternalQuantumEfficiency(X) ^■ [1 - Absorption(A) = 1 - R( ) where at any wavelength of interest λ, Ε(λ) is the number of photons in the excitation spectrum that are incident on the phosphor, R(A) is the number of photons in the spectrum of the reflected excitation light, and Ρ(λ) is the number of photons in the emission spectrum of the phosphor. This method of IQE measurement is also provided in the following work: K. Ohkubo et al., Absolute Fluorescent Quantum Efficiency of NBS Phosphor Standard Samples, 83(2) J. Ilium. Eng. Inst. Jpn. 87-93 (1999), the disclosure of which is incorporated herein by reference in its entirety.

[0057] In addition, the effect of varying dopant concentration is shown by the observing the relative reactions to light at 405 nm for PC-2, PC-5, PC-6, and PC- 7 to see the effect of 1 at% dopant, 2 at% dopant, 5 at% dopant, and 10 at% dopant respectively. The result was a blue to green shift with increasing doping, as shown in Figure 7.

[0058] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0059] The terms "a," "an," "the" and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0060] Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0061] Certain embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

[0062] In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the claims are not limited to embodiments precisely as shown and described.

Embodiments

[0063] The following embodiments are specifically contemplated by the authors of the present disclosure:

Embodiment 1 . A phosphor composition, the composition comprising a compound defined by the formula: : RE _X ; (Formula 1 )

wherein 0 < a < 3; 0 < b < 6; 0.03 < x < 0.9; M ¹ comprises Li, K, Na, or a combination thereof; M" can comprise Ba, Ca, Mg, Sr, Zn, or a combination thereof; Si is the element silicon; N is the element nitrogen; O is the element oxygen; and RE comprises Ce, Pr, Sm, Eu, Tb, or a combination thereof. Embodiment 2. The phosphor composition of embodiment 1 , where the composition comprises:

Li ₂ Ca ₆ Si ₈ .5N ₁₄ 0 ₃ :Ce ³⁺ , Li ₂ Ca ₆ Si ₈ .5N ₁₄ 0 ₃ :Eu ²⁺ , or combinations thereof.

Embodiment s. The phosphor composition of embodiment 1 , where the composition comprises: Li ₂ Ca5. ₄ Euo.6Si8.5 i ₄ 0 ₃ , Li ₂ Ca5. ₇ Euo.3Si8.5 i ₄ 03, Li ₂ Ca5.88Euo. ₁ 2Si8.5 i ₄ 03, Li ₂ Ca ₅ 9 ₄ EUo.06Si8.5 l ₄ 03,

(Lii _.8 Nao.2)Ca _5.88 Euo _. i ₂ Si ₈ .5 i ₄ 0 ₃ , Li ₂ Ca _5.88 Ceo _. i ₂ Si ₈ .5 i ₄ 03, or combinations thereof.

Embodiment 4. A phosphor element, the element comprising one or more phosphor compositions of embodiment 1.

Embodiment s. The phosphor element of embodiment 4, further comprising a sintering aid.

Embodiment 6. The phosphor element of embodiment 5, where the sintering aid is comprised of at least MgO and/or CaO.

Embodiment ?. The phosphor element of embodiment 4, wherein the element is at least about 70 T _t % for all light in the wavelength ranging from to about 310 nm to about 500 nm.

Embodiment s. The phosphor element of embodiment 4, where the phosphor composition has an emissive peak wavelength is between about 495 nm to about 620 nm.

Embodiment 9. The phosphor element of embodiment 4, where the phosphor composition has an emissive peak wavelength is between about 495 nm to about 570 nm.

Embodiment 10. The phosphor element of embodiment 4, where the phosphor composition has an emissive peak wavelength is between about 590 nm to about 620 nm.

Embodiment 1 1 . A lighting device comprising the phosphor element in embodiment 9 and an LED, wherein the element is applied directly upon the LED. Embodiment 12. The lighting device of embodiment 1 1 , wherein the LED is a blue LED.

Embodiment 13. The lighting device of embodiment 12, wherein the lighting device provides a soft white light.

Embodiment 14. A lighting device comprising the phosphor element in embodiment 10 and an LED, wherein the element is applied directly upon the LED.

Embodiment 15. The lighting device of embodiment 14, wherein the LED is a blue LED.

Embodiment 16. The lighting device of embodiment 15, wherein the lighting device provides a soft white light.