Title of Invention | EUROPIUM ACTIVATED PHOSPHOR COMPOSITION |
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Abstract | Lamps based on the Hg-discharge provide nowadays a.bout 50% of artificial light1. However, safe disposal of the burnt lamps is a serious problem as Hg is potentially hazardous causing environmental pollution. These lamps are now phased out and lamps based on LED are used in developed countries. With the advent of GaN technology LEDs emitting around 390 nm have become available. These diodes are coated with phosphor blend, which on excitation by 390 nm emit in white. During last decade solid state lighting has emerged as a new area. We have developed new, highly intense blue emitting phosphors for n-UV diodes. These phosphors will serve as indigenous replacement for blue component of phosphor blend for n-UV LED lamps. Our search for new, henceforth unreported phosphors led us to very efficient blue emitting europium doped Alkali-Alkaline Earth Halides, with a general formula where, A/*: Any alkali metal out of K, Cs or R.b M11: Any alkaline earth metal from Ca, Sr or Ba with or without Mg X: Any halide from Br or I. p and q: any integer having value 1,2 or 3. r: Activator, with concentration o.ol to 5 mole percent of M*1 |
Full Text | FORM 2 THE PATENT ACT, 1970 (39 of 1970) & The Patent Rules, 2003 PROVtSQNAU COMPLETE SPECIFICATION (see section 10 and rule 13) 1. TITLE OF THE INVENTION : Europium Activated Alkali-Alkaline Earth Halide Blue Emitting Phosphors for solid state lighting and Process of Preparation thereof 2. APPLICANT (a) NAME : Shri Ramdeobaba Kamla Nehru Engineering College, Katol Road, Nagpur (b) NATIONALITY: Indian (c) ADDRESS :Physics Department, Shri Ramdeobaba Kamla Nehru Engineering College, Gittikhadan, Katol Road, Nagpur 440 013, Maharashtra, India 3. PREAMBLE TO THE DESCRIPTION : The following specifications particularly describe and ascertain the nature of the invention and the manner in which the invention is to be performed For blue emitting component of solid state lighting phosphor blend, a composition with following formula is to be used. where, M1: Any alkali metal out of K, Cs or Rb A/": Any alkaline earth metal from Ca, Sr or Ba with or without Mg X: Any halide from Br or I. p and q: any integer having value 1,2 or 3. r: Activator, with concentration o.ol to 5 mole percent of M A process for synthesizing these phosphor composition comprises of steps- (a) dissolving alkali carbonates, alkaline earth carbonates and europium oxide in corresponding acids (i.e. HC1 or HBr or HI), (b) heating the molar mixture of (a) at 60-65°C for 12 hours to evaporate the mixture to obtain white crystalline powder (c) heating the crystalline powder as obtained in (b) to 200-250°C for two hours (d) carrying carbothermal reduction of the powder obtained in (c) for 1.5 hours at 600°C for bromides and 675°C for iodides (e) sealing the obtained composition after carrying steps sequencing from (a) to (d) in a bottle, 4. DESCRIPTION Title of the Invention Europium Activated Alkali-Alkaline Earth Halide Blue Emitting Phosphors for solid state lighting and Process of Preparation thereof Field of Invention: Solid State Lighting This invention reports a new highly efficient Blue emitting phosphor which can form a part of the blend coated on n-UV LED. The latter is a source of white light and the relevant field is Solid State Lighting. Prior Art and its drawback Fluorescent lighting originated with the observation that low pressure Hg discharge is a very efficient converter of electrical energy into UV radiation at 254 nm. It then became obvious that the low pressure Hg discharge requires suitable visible emitting phosphor in order to become a fluorescent lamp. Thus research in phosphors development continued till last decade. Afterwards threat to environment due disposal of burnt lamps became a problem of considerable magnitude. This shifted research to a non Hg source of UV. With the advent of electroluminescent GaN diode chip, very efficient solid state source of UV became available. Efforts to make lamps by coating phosphors on these diodes have met with a limited success as yet, but tremendous progress is being made in this direction worldwide. Recently, solid-state lighting based on GaN semiconductors has made remarkable breakthroughs in efficiency. GaN-based diodes emit bright violet-blue light, which can be used to pump longer wavelength phosphors. The first white light emitting diodes (LEDs) became commercially available in 1997. These white LEDs can be obtained by combining a InGaN blue LED emitting at 465 nm with a broad-band yellow phosphor, e.g. (Y.sub.l-xGd.sub.x).sub.3(Al.sub.l-yGa.sub.y).sub.50.sub.l2 (YAG:Ce). The variation of x and y can be used to produce a broad emission from 510 nm and 580 nm, leading to a high color rendering index. These white LEDs have efficiencies comparable to incandescent lights and are proving useful in a wide variety of niche lighting applications. White light can be produced by a variety of other approaches, including color mixing of three LED emissions (e.g., combining discrete blue, green, and red LEDs) or the pumping of phosphors with a deep blue/UV LED or laser diode (LD). Nitride-based vertical cavity surface emitting lasers (VCSELs), coupled with phosphors optimized for violet or near-UV absorption, offer the greatest potential for high-efficiency solid-state lighting [D. A. Steigerwald, et al]. However, the problem lies in the unavailability of suitable RGB phosphors that are optimized for absorbing the near UV or violet emission from the LEDs or lasers. The red, green and blue phosphors that are currently used in conventional fluorescent lighting have been optimized for 3 excitation by the UV emission from a mercury discharge, for which the characteristic wavelengths are 185 and 254 nm [G. Blasse, et al, 1994]. The current phosphor materials of choice for the solid-state lighting initiative are Y.sub.20.sub.2S:Eu.sup.3+ for red, ZnS:(Cu.sup.+, Al.sup.3+) for green, and BaMgAl.sub.lOO.sub.l7:Eu.sup.2+ (BAM) for blue [M. Shinoya, et al]. BAM, though tested for long, is costly component of the blend due to use of rare earth Eu.sup2+. Lamp is a commodity used by masses and about 50% of lighting need is fulfilled by artificial lighting. With a huge turnover of phosphor-blends even small drop in price will have long reaching consequences in terms of lamp price. Hence it is urgently necessary to obtain a low cost substitute for blue component of the blend. Background of invention with regards to prior art: We have taken up systematic investigations on development of phosphors for solid state lighting using indigenous raw materials and novel synthesis methods. The current invention deals with synthesis of phosphors with a general formula p.M?X qMIIX2:rEu2+, where, M1: Any alkali metal out of K, Cs or Rb M": Any alkaline earth metal from Ca, Sr or Ba with or without Mg X Any halide from Br or I. p and q: any integer having value 1,2 or 3. r: Activator, with concentration o.ol to 5 mole percent of M11 Object of the Invention It is obvious that lamp phosphors for solid state lighting must have remarkably different excitation characteristics as compared to conventional Hg discharge lamps. These phosphors must be very efficient absorber for n-UV from LED and strong emitters in red, green and blue. This patent deals with the invention of blue emitting, low cost phosphors which can be excited by near UV light, suitable for solid state lighting. We have prepared totally new, henceforth unreported, highly efficient, low cost blue emitting phosphors for SSL application. This phosphor would serve as blue component of the blend of phosphors to be applied on n-UV LED so as to convert near UV (typically 350-390 nm) emission to visible light. Summary of the Invention New, highly intense blue emitting phosphors for n-UV diodes are developed. These phosphors will serve as indigenous replacement for blue component of phosphor blend for n-UV LED lamps. The phosphors 4 p.M*X. qMf/X2:rEu2+, were prepared by wet chemical synthesis as described below. Metal carbonates of MI and Mil were dissolved in corresponding acid. The solution was then evaporated and dried at 60° C or 200°C. The resulting white dry powders were heated to carbo-thermal reduction at 600 C for bromides and 675°C for iodides. Detailed description of the Invention Fluorescent lighting originated with the observation that low pressure Hg discharge is a very efficient converter of electrical energy into UV radiation at 254 nm. It then became obvious that the low pressure Hg discharge requires suitable visible emitting phosphor in order to become a fluorescent lamp. Thus research in phosphors development continued till last decade. Afterwards threat to environment due disposal of burnt lamps became a problem of considerable magnitude. This shifted research to a non Hg source of UV. With the advent of electroluminescent GaN diode chip, very efficient solid state source of UV became available. Efforts to make lamps by coating phosphors 'on these diodes have met with a limited success as yet, but tremendous progress is being made in this direction worldwide. It is obvious that lamp phosphors for solid state lighting must have remarkably different excitation characteristics as compared to conventional Hg discharge lamps. These phosphors must be very efficient absorber for n-UV from LED and strong emitters in red, green and blue. In this regard, we have prepared totally new, henceforth unreported highly efficient blue emitting phosphors for SSL application having general formula p.M*X. qMIIX2:rEu2*. This phosphor would serve as blue component of the blend of phosphors to be applied on n-UV LED so as to convert near UV (typically 350-390 nm) emission to visible light. These phosphors have not been patented so far. These phosphors will serve as indigenous replacement for blue component of phosphor blend for n-UV LED lamps. 1. Typical preparation of KBr.CaBr2:Eu2+: KBr.Cao.99Br2:Eu 0.01: was prepared by wet chemical synthesis. Calculated weights of K2CO3 (1 g), CaC03(l .4340 g), Eu203 (0.0255 g) were dissolved in 48% HBr (4.9112 ml). The solution was heated on hot plate at 60 C for 12 hours. Solid powder was then heated for 2 hours at 200 C. Resulting sample was heated by carbothermal reduction at 600°C for 1.5 hours. Resulting sample was collected and sealed into a bottle. Graphs of the following phosphors are being provided in Fig. 1. 2. a)Typical preparation of KL SrfaEu2*: KI.Sro.995l2:Eu2+o.oo5- was prepared by wet chemical synthesis. Calculated weights of K2CO3 (1 g), SrC03(2.1228 g), Eu203 (0.0127 g) were dissolved in HI (5.487 ml). The solution was heated on hot plate at 60°C for 12 hours. Solid powder was then heated for 2 hours at 200°C. Resulting sample was heated by carbothermal reduction at 675°C for 1.5 hours. Resulting sample was collected and sealed into a bottle. Graphs of the following phosphors are being provided in Fig. 2. General Formula Phosphors for which graphs are provided KL SrI2:Eu2+ KI.Sro.995l2"Eu 0.005 KI.Cao.995l2;Eu 0.005 3. Typical preparation of KI. 2Bah:Ei?*KI.2Bao.99sl2:Eu2+o.oi: was prepared by wet chemical synthesis. Calculated weights of K2C03 (1 g), Ba2CO3(1.4340 g), Eu203 (0.0255 g) were dissolved in HI (4.1646 ml). The solution was heated on hot plate at 60°C for 12 hours. Solid powder was then heated for 2 hours at 250°C. Resulting sample was heated by carbothermal reduction at 675°C for 1.5 hours. Resulting sample was collected and sealed into a bottle. Graphs of the following phosphors are being provided in Fig. 3. Genera? Formula | Phosphors for which graphs are provided 4. Typical preparation of 2CsCl. CaCfaEu2* 2CsCl.Cao.999Cl2:Eu2+o.oo]-' was prepared by wet chemical synthesis. Calculated weights of CsCl(l g), CaCO3(0.2990 g), Eu203 (0.0005 g) were dissolved in HCl (1.0487 ml). The solution was heated on hot plate at 60°C for 12 hours. Solid powder was then heated for 2 hours at 200°C. Resulting sample was heated by carbothermal reduction at 600°C for 1.5 hours. Resulting sample was collected and sealed into a bottle. Graphs of the following phosphors are being provided :Photoluminescence spectra in Fig. 4 and XRD pattern in Fig.5. 5. CLAIMS We claim: 1. Fluorescent composition for generating blue colour in solid state lighting having Europium activated alkali-alkaline earth halide compounds having a general formula p.M*X. qMllX2:rEu2+ wherein, M1: Any alkali metal K or Cs or Rb M11-. Any alkaline earth metal from Ca or Sr or Ba X: Any halide from Br or I, p and q: any integer having value 1 or 2 or 3, r. Activator, with concentration o.ol to 5 mole percent ofM*1, 2. A europium activated phosphor composition as claimed in claim 1, wherein the composition is KBr.Cao.999Br2:Eu o.ooi, 3. A europium activated phosphor composition as claimed in claim 1, wherein the composition is KI.Sro.995i2:Eu "Vww, 4. A europium activated phosphor composition as claimed in claim 1, wherein the composition is 2CsCl.Cao.995Cl2:Eu Voos, 5. A europium activated phosphor composition as claimed in claim 1, wherein the composition is KI.Sro.99si2:Eu2+o.oo5, 6. A process for synthesizing a rare earth activated phosphor composition as claimed in preceding claims, said process comprising steps: (a) dissolving alkali carbonates, alkaline earth carbonates and europium oxide in corresponding acids (i.e. HC1 or HBr or HI), (b) heating the molar mixture of (a) at 60-65°C for 1-12 hours to evaporate the mixture to obtain white crystalline powder (c) heating the crystalline powder as obtained in (b) to 200-250°C for 1-12 hours (d) carrying carbothermal reduction of the powder obtained in (c) for 1.5-12 hours (e) sealing the obtained composition after carrying steps sequencing from (a) to (d) in a bottle, 7. A process as claimed in claim 6 above, wherein step (b), (evaporation) is carried out at a temperature range of 60-65°C for 1-2 hours, 8. A process as claimed in claim 6 above, wherein step (c), is carried out at a temperature range of 200-250°C for 2 hours, 9. A process as cfaimed in claim 6 above, wherein step (d), carbothermal reduction is carried out at a temperature range of 600-675°C for 1.5-2 hours, 10. Fluorescent composition for generating blue colour in solid state lighting having ns activated alkali-alkaline earth oxide compounds having a general formula pJntX. qMIIX2:rEu2+ to be used as blue emitting component of the blend of Solid State Lighting Phosphor as used in n-UV LED substantially such as herein described with drawings and foregoing examples 6. DATE AND SIGNATURE Date Dec 20, 2008 Signature Principal (V.S.Deshpande) Shri Ramdeobatia Kami*Beftm . . , „„.„-„ .. |
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80-MUM-2009-CLAIMS(AMENDED)-(22-3-2013).pdf
80-MUM-2009-CORRESPONDENCE(27-8-2012).pdf
80-mum-2009-correspondence.pdf
80-mum-2009-description(complete).doc
80-mum-2009-description(complete).pdf
80-MUM-2009-FORM 13(24-8-2012).pdf
80-MUM-2009-FORM 2(TITLE PAGE)-(22-3-2013).pdf
80-mum-2009-form 2(title page).pdf
80-MUM-2009-REPLY TO EXAMINATION REPORT(24-8-2012).pdf
80-MUM-2009-REPLY TO HEARING(22-3-2013).pdf
Patent Number | 256570 | ||||||||||||
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Indian Patent Application Number | 80/MUM/2009 | ||||||||||||
PG Journal Number | 27/2013 | ||||||||||||
Publication Date | 05-Jul-2013 | ||||||||||||
Grant Date | 03-Jul-2013 | ||||||||||||
Date of Filing | 13-Jan-2009 | ||||||||||||
Name of Patentee | RAMDEOBABA KAMLA NEHRU ENGINEERING COLLEGE (RKNEC) | ||||||||||||
Applicant Address | PHYSICS DEPARTMENT, SHRI RAMDEOBABA KAMLA NEHRU ENGINEERING COLLEGE, GITTIKHADAN, KATOL ROAD, NAGPUR 440 013, MAHARASHTRA, INDIA. | ||||||||||||
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PCT International Classification Number | C01F17/00 | ||||||||||||
PCT International Application Number | N/A | ||||||||||||
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