I HC THI NGUYN TRNG I HC KHOA HC BO CO TNG KT TI KHOA HC V CNG NGH CP I HC NGHIN CU CH TO BT HUNH QUANG PHT X NH SNG (RED) NG DNG TRONG CH TO N HUNH QUANG M s: H2011-07-08 Ch nhim ti: Th.S. L Tin H THI NGUYN, NM 2013 I HC THI NGUYN TRNG I HC KHOA HC BO CO TNG KT TI KHOA HC V CNG NGH CP I HC NGHIN CU CH TO BT HUNH QUANG PHT X NH SNG (RED) NG DNG TRONG CH TO N HUNH QUANG M s: H2011-07-08 Ch nhim ti: Th. S. L Tin H Ngi tham gia thc hin: PGS. TS. Phm Thnh Huy PGS. TS. V Th Kim Lin TS. Chu Vit H Xc nhn ca c quan ch tr ti (k, h tn, ng du) THI NGUYN, NM 2013 1 M U 1. Tnh cp thit ca ti Hin nay, vn nng lng, tit kim nng lng v nng lng sch bo v mi trngangcquantm,ut,nghincutrntonthgii.ivinnglng chiu sng, theo bo co mi nht ca IEA (Policies for Energy efficient lighting [22]) ch tnh ring cc n chiu sng dy tc tiu th khong 7% tng lng in nng tiu th (bngtngcngsutcattcccnhmyinhtnhn).Trongnm2005,tng lng in nng tiu th ca cc loi n dy tc l ~ 970 TWh, vic ch to v s dng cc bng n ny thi ra mi trng mt khi lng ln ~ 560 Mt (CO2), v thy ngn. V vy vic thay th cc thit b chiu sng ni chung v cc n chiu sng bng dy tc ni ring bng cc bng n hunh quangv hunh quang compac lnhu cu cp thit ca nhiu quc gia trn ton th gii, trong c Vit Nam. nc ta hin nay, nguyn liu bt hunh quang dngtrong cc bngnhunh quangvbngnhunhquangbaphaslnhptncngoi.Vicchtobt hunhquangngdngphtrongccnhunhquanglnhucucpthitvsng cn ca cc nhmy sn xut thit b chiu sng,vkhi ch ng c nguynvt liu mi ch ng c cng ngh ch to v h c gi thng sn phm. Trong cc thit b chiu sngpht nh sng trng dngvt liu ba ph th bt hunh quangpht ra bc x mu chim gn 80%. V vy vic nghin cu v ch to bt hunh quang pht bc x mu l cn thit. ti Nghin cu ch to bt hunh quang pht x nh sng (Red)ng dng trong ch to n hunhquang c thc hinnhmng dng trc tipccktquvovicchtoccnhunhquangnhsngdngtrongnng nghip v n hunh quang compact hiu sut cao. 2. Mc tiu nghin cuChtobthunhquangphtxnhsng(Red),nghincucccchnh hngn cu trcv tnh cht quang cabthunhquang, ph th btln bng n hunh quang. 3. i tng v phm vi nghin cu Cc bt hunh quang c pha tp Eu vi cc vt liu nn khc nhau, ng dng trong ch to n hunh quang ba ph. 2 4. Ni dung nghin cu 1.Tng hp bt hunh quang pht ra bc x mu , ng dng trong ch to n hunh quang ba ph. 2.Khostccyutnhhngncutrcvtnhchtquangcavtliu tng hp c. 5. Phng php nghin cu- Thc nghim tng hp bt hunh quang. -ThcnghimchpnhSEM,ophnhiuxtiaX,phkchthchhunh quang, ph quang hunh quang. - Tp hp v x l s liu 3 Chng 1 TNG QUAN Hinnay,cngnghchiusngtitkiminnngvthnthinvimitrng ang c quan tm nghin cu. Thc t cho thy, xu hng s dng cc ngun sng nhn to l cc loi n hunh quang lm ngun sng ch yu ngy cng nhiu, khin cc nh cung cp ngun sng ngy cngquantmnhiuncngngh,nguynvtliutorachtlngnhsngtt hn. Cc loi bt hunh quang c di sng hp, c quang thng ln v ch s truyn mu cao ang ha hnng dng rt nhiu trongvic ch to cc loi bngn hunh quang tit kim nng lng v cht to cc loi it pht quang Vit Nam.Nh chng ta bit, cc loi bng n hunh quang sn xut ti Vit Nam hu ht l s dng bt ba mu ngoi nhp nn khng ch ng trong sn xut, m gi thnh sn phm li cao. V vy, vic nghin cu cng ngh ch to bt hunh quang ba mu c hiu sut cao thay th cho bt hunh quang ngoi nhp gim gi thnh sn xut l mt trong nhng nhu cu cp thit, c ngha thc tin cao v rt cn thit.1.1.Tng quan v bt hunh quang Vt liu hunh quang c nghin cu ch to ti l vt liu c kh nng pht nh sng trong vng quang ph m mt ngi cm nhn c khi b kch thch. Hin tng khi cc cht nhn nng lng kch thch t bn ngoi v pht ra nh sngcgilsphtquang.Tytheoccloinnglngkchthchkhcnhau ngi ta phn thnh cc loi hunh quang khc nhau: nng lng kch thch bng nh sng c gi l quang pht quang; nng lng kch thch bng in trng c gi linquangphtquangvvQutrnhphtquangxyrangaysaukhickch thch (F ns) c gi l hunh quang. Cn nu qu trnh pht quang xy ra chm (F s) th c gi l s ln quang. Khi hp th nng lng kch thch, nguyn t, phn t chuyn t mc nng lng ban u ln cc trng thi nng lngkhc cao hn. Nu phn t, nguyn t hp th nh sng nm trong vng nhn thy hoc vng t ngoi th nng lng hp th s ng vi cc mc in t, nh vy s c s chuyn di ca in t trong phn t t qu o ny sangqu okhc. T trng thikch thch, in t trong nguynt, phn t c 4 thtrvtrngthicbnbngccconngkhcnhau:hiphckhngbcx hoc hi phc bc x. 1.1.1.C ch pht quang ca bt hunh quang C ch pht quang ca vt liu ph thuc vo cu hnh in t ca cc nguyn t t him pha tp, c vai tr l cc tm pht x. i vi vt liu hunh quang pha tp gm hai phn chnh: + Cht nn (mng ch) l nhng cht c vng cm rng do c cu to t cc ion c cu hnh in t lp y nn thng khng hp th nh sng nhn thy. + Chtphatp(tmkchhot)lnhngnguynthayionccuhnhint vi mt s lp ch lp y mt phn (v d nh cc ion kim loi chuyn tip c lp d chablpy,ccionthimclpfchablpy)scnhngmcnng lngcchnhaubinhngkhekhnglnlmtngngvinnglngnhsng nhn thy, ta ni chng nhy quang hc. Khi kch thch vt liu bng bc x in t, cc photon b vt liu hp th. S hp th c th xy ra ti chnh tm kch hot hoc ti cht nn. Trng hp th nht: Tm kch hot hp th photon, n s chuyn t trng thi c bn ln trng thi kch thch, qu trnh quay tr v s bc x nh sng. Trng hp th hai: Cht nn hp th photon, khi in t vng ha tr s nhy ln vng dn lm sinh ra mt l trng vng ha tr. S ti hp gia in t vng dn v l trng vng ha tr thng khng xy ra m in t v l trng c th s b by ti cc by, s ti hp gia in t v l trng lc ny s khng bc x nh sng. Mt kh nng na c th xy ra khi cht nn hp th photon l in t khng nhy hn t vng ha tr ln vng dnm ch nhy ln mtmc nng lng gn y vng dn, lc ny in t v l trng khng hon ton c lp vi nhau m gia chng c mt mi lin kt thng qua tng tc tnh in Coulomb. Trng thi ny c gi l exciton, n c nng lng lin kt nh hn mt cht so vi nng lng vng cm Eg. Bn knh Bohr exciton (aB) c tnh theo cng thc sau: oB 2 * *o e h4 1 1a ( )m e m mtc c= + Trong , 0 l hng s in, l hng s in mi ca vt liu, mo l khi lng ngh ca in t, me* v mh* l khi lng hiu dng (l khi lng tnh n nhng 5 tc ng ca trng tinh th ln tnh cht ca cc ht ti) tng ng ca in t v l trng. S ti hp exciton s bc x nh sng. 1.1.2.Cc c trng ca bt hunh quang Hiu sut hunh quang. Hiu sut hunh quang c tnh bng tng hiu sut hp th v hiu sut lng t. Trong : Hiu sut lng t c tnh bngcng sut pht x chia cho cng suthp th. Mi loi vt liu hunh quang cn c tnh ton sao cho hiu sut hunh quang cao nht. Thng thng bng n hunh quang c th t hiu sut hunh quang t 0.55-0.95Hp th bc x kch thch. i vi vt liu hunh quang ni chung vng hp th nng lng khng phi l mt di um thng lhpthmnh trongmtvngnht nh.Trong bng n hi thy ngnpsutthpbcxkchthchcanmnhnhtbcsng254nm,vtliu hunhquangchoncncphhpthmnhtrongdiny.ivibngnhunh quang hi thy ngn p sut cao c hai vng bc x l 220-290nm v 330-390nm do loi vt liu hunh quang hp th di bc sng 380nm cng cn c ch . n nh mu Mt s loivt liu hunh quang c tnh cht quangbin i theo nhit . VD bthunhquanghalophosphats3Ca(PO4)Ca(F,Cl)chothobiSb3+ vMn2+, ph bc x caSb3+ b dchv pha bc sng ngnkhi nhit tng,LaPO4:Ce,Tb hiu sut pht quang gim n 90% khi nhit tng t nhit phng ln 1500C. i vibngnhunhquanghithyngnpsutthp,nhithotngcan khong400C,ivinthyngnpsutcao,nhitbntrongcthtngn 3500C v th cn phi c nhng loi hunh quang ph hp. bn C rt nhiu tc nhn gy ra s suy gim phm cht ca vt liu nh tc ng ca ha, nhit, in trng v c hc xy ra bn trong. i vi bng n hunh quang hi thy ngn p sut thp, vt liu hunh quang cn c tnh tr vi hi thy ngn, khng b phn hy bi cc bc x nng lng cao. Khng tng tc vi cc ion tp cht ca vt liu lm thnh ng. ng u v hnh dng v kch thc ht Trong khi vt liu hunh quang, sau khi s pht quang din ra cc tia bc x s b tn x, khc x v tng tc vi cc ht vt liu. Thng thng qu trnh ny s lm 6 mt i mt phn nng lng bc x do tn x v hp th ca khi vt liu. Do vy, s phn b v hnh dng cng nh kch thc ca cc ht cng c vai tr quan trng nh hng ti hiu sut pht quang. 1.2.Cc loi bt hunh quang 1.2.1.Bt hunh quang truyn thng Bthunhquangtruynthnglccbthunhquangdatrnnguynliu calciumhalophosphate.Bthunhquangcalciumhalophosphatepngcs kch thch ca bc x 254 nm ca thy ngn v bn trong khng gian phng in ca mi trng kh tr. Bt hunh quang quang calcium halophosphate c hot ha vi cc ion Sb3+ v Mn2+ ( c cng b bi Mckeag v cng s nm 1942). T bt hunh quang halophosphate c cc ion kch hot Sb3+ v Mn2+ c s dng rng ri cho s pht ra nh sng trng trong bng n hunh quang cng nghip. 1.2.1.1.Cu trc mng nn HalophosphatevithnhphnCa5(PO4)3X(X=F,Cl)lgnvihydroxy-apatite, thnh phn chnh ca xng v rn. Apatite c cu trc tinh th l hexagonan v cc nguyn t Ca xut hin hai v tr khc nhau. Cc nguyn t Ca v tr 1 ( CaI) c s phi tr 6 v c bao quanh bi 6 nguyn t O vi di trung bnh ca lin kt CaI-O l 2,43 A0. Cc nguyn t Ca v tr 2 ( CaII) c bao quanh bi 6 nguyn t oxi ( di trung bnh ca lin kt CaII-O l 2,43 A0) v mt nguyn t halogen( di lin kt CaII-O l 2,39 A0. Trong trng hp halogen l F th CaII v nhng nguyn t F cng nm trn mtmtphngtinhth.TuynhinlkhihalogenlClthCaIvnhngnguyntCl khng nm trn cng mt mt tinh th. Mt d c nhiu bi bo bn v v tr ca Sb3+ v Mn2+ nhng tt c u nht tr cho rng nhng ion ny c kh nng thay th cc ion Ca2+ c 2 v tr. Ngoi ra tc gi Blasse cng nhn mnh rng c bng chng cho thy cc ion Sb3+ cng c th v tr trn phosphorus trong mng li bt hunh quang. TuynhintrongkhinhngionMn2+nichungthngphnbngutrong ton tinh th th nhng ion Sb3+ c tm thy hu ht trn b mt tinh th [11,26]. 1.2.1.2.Tnh cht pht quang ca vt liu Cc bng n hunh quang thng s dng bt halophosphat vi pht x ch yu l ca cc ion Sb3+ v Mn2+ c pha tp. Bt hunh quang halophosphate hot ha bi Sb3+ v Mn2+ hp th bc x t ngoi t hi thy ngn trong n hunh quang v pht ra nh sng trng (hnh 1.1). Qu trnh pht ra nh sng trng c quy cho s hp th bc 7 x hi thy ngn 254nm bi nhng ion hot ha Sb3+ v pht ra nh sng blue (xanh da tri). Mt phn nng lng hp th bi Sb3+ truyn cho nhng ion hot ha Mn2+ v pht ra nh sng red-orange ( - cam). Nhng ion Mn2+ hu nh khng hp th bc x ca hi thy ngn. S kt hp ca cc nh sng blue v red-orange sinh ra nh sng trng[11]. Sb3+ c vng bc x 480 nm v Mn2+ c vng bc x ~ 580 nm (hnh 1.2). Hnh 1.1. Ph pht hunh quang ca calcium halophosphate A: Sb3+, B: Mn2+, C: Halophosphate pht nh sng trng [11] Hnh 1.2 Ph hunh quang ca bng n s dng bt halophosphat 1.2.1.3.u nhc im ca bt halophosphate Mt trong nhng u im ln nht ca bt halophosphate l nguyn liu r, d ch to. Tuy nhin, mt hn ch ln ca bt hunh quang halophosphate l khng th t c ng thi sngcaov h s trmu cao. C th:Nu sng cao (hiu 8 sut pht quang khong 80 lm/W), h s tr mu (CRI) khong 60. Gi tr CRI c th c ci thin ln n 90 nhng sng gim khong 50 lm/W [11].Bthunhquanghalophosphatechiusutphtquangvkhnngduytr hunh quang thp. Nguyn nhn l do cc tm hp th to ra t cc bc x t ngoi kh kin, l cc tm pht x, gi l cc tm mu v cc khuyt tt mng. Nhng tm munychnhthnhkhikhuyt tttrongmngnnhalophosphateby 1 electron hocmtltrng.Cctmmunytoramtshpthcaccbcxkchthch trong c vng ph t t ngoi xa n hng ngoi. V vy nhng tm mu ny c th lm gim hoc bin i sng ca bt hunh quang do hp th s pht x nhnh thy ca bt hunh quang hoc hp thmt phn bc x kch thch 254 nm ca hi thy ngn [26]. 1.2.2.Bt hunh quang ba ph Bthunhquangbaphlbthunhquangcchtocshothaca cc ion t him pht x ra ba mu c bn nhm to ra nh sng trng. Cc nguyn t thimthngcsdngbaogmSc,Y,Lavccnguynthlantanit.H lantanit(Ln)gm14nguynt4fcsthtt58n71trongbngtunhon Menleep. Nhvy, ccnguyn tt him thuc nhmIIIBv chuk 6 ca bng tun hon cc nguyn t ha hc.Cu hnh electron ca cc nguyn t nguyn t t him c th c biu din bngcngthcchungnhsau:1s22s22p63s23p63d104s24p64d104fn5s25p65dm6s2,trong : n thay i t 0 14, m ch nhn gi tr 0 hoc 1. Davo c im sp xp electron trn phnlp 4f m cc lantanit c chia thnh hai phn nhm: Phn nhm nh (phn nhm xeri) gm 7 nguyn t, t CeGd: CePrNdPmSmEuGd 4f2 4f3 4f4 4f5 4f6 4f7 4f75d1 Phn nhm nng (phn nhm tecbi) gm 7 nguyn t, t TbLu: TbDyHoErTuYbLu 4f7+2 4f7+34f7+44f7+54f7+64f7+74f7+75d1 Tnhchthohccaccionthimchotr3tngtnhauvlp vintcachnguccuhnh[Xe]4fN-15d16s2.HLantanitbtut nguyntLa3+vilpv4fhontontrng(4f0),tipCe3+cmtint 9 (4f1),sint4ftngdnlntheosutdychonYb3+vi13int(4f13) v hon ton lp y cu hnh 4f14 ng vi Lu3+. Nhng c tnh quan trng ca cc ion t him l pht x v hp th di snghp,thigiansngcctrngthigibncao,ccchuynmcphtxra photon c bc sng thch hp trong pht quang do lp 4f c nh x cao nm gn lihtnhn nguyn t.L thuyt gii thch cho hin tng ny c a ra ln u tin bi M.Mayer v cng s vo nm 1941. ng tnh ton cu trc nguyn t ca cc nguyn t thuc nhmLantan. Khi xem xt bc tranh c inv cc nguyn t, th thy rng ht nhn c bao bc bi cc lp v in t, cc lp ny c in y mt cch t t khi tin dn theo chiu tng in tch ca bng h thng tun hon. Hnhnhquangphcaccnguyntthimcquanstlnutinvo nhngnm1900biJ.Becquerel.lquangphvchcamuithimc lm lnh xung nhit thp (