Acoustic investigations on PbO Al 2 O 3 B 2 O 3 glasses doped with certain rare earth ions

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1 Bull. Mtr. Si., Vol. 4, No. 1, Frury 001, pp Inin Amy of Sins. Aousti invstigtions on PO Al O 3 B O 3 glsss op with rtin rr rth ions M RAMI REDDY, S BANGARU RAJU n N VEERAIAH* Dprtmnt of Physis, Ngrjun Univrsity Post Grut Cntr, Nuzvi 51 01, Ini Dprtmnt of Physis, AU Collg of Sin n Thnology, Anhr Univrsity, Viskhptnm , Ini MS riv 0 My 000; rvis 5 Novmr 000 Astrt. Elsti mouli (Y, η), Poisson s rtio (σ), mirohrnss (H) n som thrmoynmil prmtrs suh s Dy tmprtur (θ D ), iffusion onstnt (D i ), ltnt ht of mlting ( H m ) t of PO Al O 3 B O 3 glsss op with rr rth ions viz. Pr 3+, N 3+, Sm 3+, Eu 3+, T 3+, Dy 3+, Ho 3+, Er 3+ n Y 3+, r stui s funtions of tmprturs (in th tmprtur rng C) y ultrsoni thniqus. All ths prmtrs r foun to inrs with inrsing tomi numr Z of th rr rth ions n foun to rs with inrsing tmprtur of msurmnt. From ths rsults (togthr with IR sptr of ths glsss), n ttmpt is m to throw som light on th mhnil strngth of ths glsss. Kywors. PO Al O 3 B O 3 glsss; rr rth ions; lsti mouli. 1. Introution Th stuy of lsti/ousti n thrmoynmi proprtis of glsss hlps in ssssing thir mhnil strngth. Work long ths lins ws rri out in rnt yrs on vrity of inorgni glsss giving vlul informtion (Singh t l 199; Mllwny 1994; Stynryn n Buhuu 1994; Rvikumr n Vrih 1997; Kumr n Vrih 1999). Svrl physil proprtis of lkli/ lklin rth lumino ort glsss, in prtiulr, thos ontining iffrnt trnsition n rr rth mtl ions hv lso n unr xtnsiv invstigtions in rnt yrs (Nhimuttu n Jgnnthn 1995; Khlif t l 1996). Howvr, th lkli fr lumino ort glsss lik PO Al O 3 B O 3 glsss r moistur rsistnt, possss low rts of rystlliztion n high ltril rsistn. In ontrst to lkli or lklin rth oxis, PO hs th ility to form stl glss u to its ul rol, on s th moifir (if P O is ioni) n th othr s glss formr (if P O is ovlnt). In ition, luminium n oupy oth ttrhron (ntwork forming), n othrl (moifying) stts, in ths glsss. Furthr, ths glsss r optilly trnsprnt to th short wvlngth rgion (nssry for gtting optimum ffiiny from optil pumping of lsing ions) n high wvlngth rgion (nssry for gtting th mximum output intnsity from lsr rition); in viw of ths qulitis ths glsss r onsir s goo hosts for lsing rr rth ions (suh s Pr 3+, N 3+, Eu 3+, T 3+ t). Thus it is flt usful to throw som light on mhnil strngth of *Author for orrsponn ths lsr mitting glsss y stuying thir lsti proprtis. Rntly, w hv rport th rsults of our stuis on ltril n rtin optil proprtis of PO Al O 3 B O 3 glsss (Ngswr Ro n Vrih 000; Rmi Ry t l 000); ths stuis hv yil vlul informtion rgring insulting n othr ft ontroll proprtis of ths glsss. This ppr rports th rsults of til invstigtions on vrious ousti n thrmoynmi proprtis of PO Al O 3 B O 3 glsss op with rr rth ions, viz. Pr 3+, N 3+, Sm 3+, Eu 3+, T 3+, Dy 3+, Ho 3+, Er 3+ n Y 3+ in th tmprtur rng C y ultrsoni thniqus.. Exprimntl For th prsnt stuy, prtiulr omposition 19PO 5Al O 3 76B O 3 : 1Ln O 3, (ll in mol%) ws hosn. Approprit mounts of Anlr gr rgnts of PO, Al O 3, B O 3 n Ln O 3 wr thoroughly mix n ll th smpls wr mlt t out 1150 ± 10 C in pltinum ruil for out h until ul fr liqui ws form. Th mlt ws thn pour into rss moul with nrrow rtngulr hol for longituinl osilltion msurmnts n into rss moul with ylinril hol for torsionl osilltion msurmnts, n thy wr susquntly nnl t 300 C. Th morphous stt of th smpls ws hk y X- ry iffrtion sptr ror on Sifrt Diffrtomtr mol SO-Dy Flux 00 with oppr trgt n nikl filtr oprt t 40 kv, 30 ma. Th nsity () of th glsss ws trmin to n ury of

2 64 M Rmi Ry, S Bngru Rju n N Vrih y th Arhims Prinipl using xyln (99 99% pur) s th uoynt liqui. Sin th ultrsoni msurmnts on th prsnt smpls wr m in th tmprtur rng low 00 C, whih is fr low whn ompr with th mlting tmprtur of th glsss ( 1150 C), nsity of th smpls in th ntir prsnt xprimntl rng of tmprtur, ws tkn s onstnt. Th glsss wr thn groun n finly polish. Th finl imnsions of th glsss us for longituinl ( m) n shr ( m long n 0 5 m in imtr) vloity msurmnts wr lmost intil to thos of X-ut 0 13 MHz qurtz trnsurs us in th msurmnts. Th ultrsoni vloitis in th smpls wr msur with pizoltri omposit osilltor pprtus (Mittl Entrpriss, Nw Dlhi). If f q n f r th rsonn frqunis of th trnsur n th omposit r, rsptivly, th rsonnt frquny ( f s ) of th glss smpls ws trmin using th rltion: f s = f + m / m )( f f ), (1) ( q s q whr m q n m r th msss of th trnsur n glss smpl, rsptivly. For msuring th tmprtur vrition of f s, th hsiv us for mnting th glss smpl with qurtz trnsur ws vry thin lyr of pst ontining lium ront n soium silit in 1 : 5 rtio y wight n th systm work stisftorily ftr it ws kpt for on full y unr prssur t room tmprtur. Th rsonnt frqunis t high tmprturs wr msur y kping th omposit r long with th holr t th ntr of n ltri furn whos rt of hting ws mintin t 50 C/h with snsitiv PID tmprtur ontrollr. Th ury of th tmprtur ontrol in ths msurmnts ws ± 0 5 C. 3. Rsults From th msur vlus of nsity () n lult vrg molulr wight M, vrious physil prmtrs suh s Ln 3+ ion onntrtion, N i, mn Ln 3+ ion sprtion istn, R i, n fil strngth, F i, whih r usful for unrstning th lsti proprtis of ths glsss r vlut n prsnt in tl 1. Figur 1A shows longituinl rsonn urvs otin t room tmprtur for PO Al O 3 B O 3 glsss op with four iffrnt rr rth ions viz. Pr 3+, Eu 3+, T 3+ n Y 3+ ; it is osrv tht ths rsonn urvs xhiit th shrpning of th pks with shift in th rsonn frquny towrs highr frqunis with sning pk hights s th tomi numr Z of th rr rth ion is inrs. Figur 1B shows th longituinl rsonn urvs of Pr 3+ op PO Al O 3 B O 3 glsss rwn t iffrnt tmprturs; w osrv th roning of th rsonn urvs with rsonn frquny ing shift towrs th lowr frqunis with inrsing hlf withs n sning pk hights, with inrs in th tmprturs of msurmnts. Similr vritions in th rsonn urvs with tmprturs wr osrv for ll othr smpls. Th torsionl rsonn urvs hv lso xhiit similr hviour. From th rsonn frqunis, th longituinl (V l ) n shr (V s ) vloitis wr trmin y th rltionship V l or s = Lf s (whr L is th lngth of th spimn). From th vritions of f s with tmprtur, th orrsponing longituinl n shr vloitis of th soun wvs in th spimns wr vlut t iffrnt tmprturs. Using ths vloitis, Young s moulus, Y, n shr moulus, η, wr trmin t iffrnt tmprturs for ll th smpls. Furthr using th rltionships n Y = (1 + σ ), () η H = ( 1 σ ) Y / 6(1 + σ ), (3) th Poisson s rtio, σ, n mirohrnss, H, of th glsss wr vlut n prsnt in tl. Th vrition of mhnil loss ftor or th intrnl frition, Q 1, with tomi numr, Z, of rr rth ions, vlut t two iffrnt tmprturs (viz. t 30 n 100 C) using Tl 1. Vrious physil proprtis of PO Al O 3 B O 3 : Ln 3+ glsss. Glss (g/m 3 ) M N i (10 ions/m 3 ) R i (Å) F i (10 16 m ) N[E F ] (10 0 V 1 /m 3 ) Pr N Sm Eu T Dy Ho Er Y

3 Aousti invstigtions on PO Al O 3 B O 3 glsss 65 Q 1 = f 3 f r, (4) (whr f is th hlf with of th rsonn urvs) is shown in figur ; th vlu of Q 1 is foun to rs with inrs in th tomi numr, Z, of th oping ion n foun to inrs with inrs in th tmprtur of msurmnt. Th vlus of Young s moulus, Y, n rigiity moulus, η, t room tmprtur for pur PO Al O 3 B O 3 glsss r foun to 58 5 n 6 3 GP rsptivly; whn ths glsss r op with Pr 3+ ions, th vlus of Y n η rs to 55 3 n 7 rsptivly. Howvr, th sussiv inrs in th tomi numr, Z, of th opnt us grul inrs in ths vlus (figur 3). Figur 4 shows th vrition of Y n η with tmprtur for som of th smpls; with inrs in Amplitu A tmprtur, th vlus of Y r foun to rs slowly up to out 60 C n yon tht th rt of rs is onsirly highr for ll th smpls. Howvr, th rs in th vlus of η with tmprtur up to 00 C is osrv to only out 4 10%. Th vrg soun vloity for ths glsss ws trmin using th rltionship (Ll n Singh 1993) V 1/ m [ Vl (4/ 3) Vs ] =. (5) Using this vloity, th Dy tmprtur, θ D, of th glsss ws lso trmin using th rltionship 1/ 3 h 3N A θ D = Vm, (6) K 4πV whr h is Plnk s onstnt, K, th Boltzmnn s onstnt, N A, th Avgro s numr n V, th spifi volum (volum oupi y th unit mss of th glss) n its vrition with tomi numr, Z, of th rr rth ions t fiv iffrnt tmprturs is shown in figur 5. Amplitu B Frquny, M Hz Figur 1. A. Longituinl rsonn urvs of PO Al O 3 B O 3 glsss op with iffrnt rr rth ions () Pr 3+, () Eu 3+, () T 3+ n () Y 3+ n B. longituinl rsonn urvs of PO Al O 3 B O 3 glsss op with Pr 3+ t iffrnt tmprturs: () 30, () 100 n () 160 C. Tl. Dt on som lsti proprtis of rr rth ion op PO Al O 3 B O 3 glsss. Y (GP) η (GP) σ H (GP) Glss 30 C 100 C 30 C 100 C 30 C 30 C Pur Pr N Sm Eu T Dy Ho Er Y Q -1 x Y ( G P) 57 Y η η ( G P) Atomi no Z Figur. Vrition of intrnl frition, Q 1 with tomi numr, Z of th rr-rth opnts of PO Al O 3 B O 3 glsss t. 30 n. 100 C Atomi numr Z Figur 3. Vrition of Young s moulus, Y n rigiity moulus, η with tomi numr, Z of th rr-rth opnts of PO Al O 3 B O 3 glsss t room tmprtur. 4.5

4 66 M Rmi Ry, S Bngru Rju n N Vrih Th ousti impn for ths glsss ws lso trmin y th rltionship Z i = V m. (7) Furthr, ltnt ht of mlting, H m n th iffusion onstnt D i, givn y th rltionships H m 9M θ Dri K =, (8) 18 h i D = Kr θ / 96h, (9) i D wr lso vlut for ths glsss. All ths prmtrs viz. th vrg soun vloity, V m (figur 6), th Dy tmprtur, θ D (figur 5), th ltnt ht of mlting, H m (figur 7) n th iffusion onstnt, D i (figur 8) wr foun to inrs t fstr rts with inrs in th tomi numr of Ln 3+ ions in th ginning of th sris n sm to ttin sturt vlus t th n of th sris. 4. Disussion In gnrl, th proprtis of glss pns upon its omposition n to onsirl xtnt upon its strutur. L lumino ort glsss op with rr rth ions hv omplx ompositions n r n mixtur of ntwork formrs n moifirs. B O 3 is wll known ntwork formr with BO 3 struturl units. Th prsn of BO 4 units in ths glsss is lso onfirm from th infrr sptr of ths glsss (figur 9); IR sptr of PO Al O 3 B O 3 glsss ror t room tmprtur in th frquny rng m 1 hv xhiit thr groups of ns: (i) in th rgion m 1, u to strthing virtions of B O on of trigonl BO 3 units, (ii) in th rgion m 1 whih r u to B O on strthing of th ttrhrl BO 4 units n (iii) n roun 700 m 1 u to th ning of B O B linkgs in ort ntwork. In ition wk ut finit n roun 550 m 1 is lso osrv; this is initiv of th prsn of PO 4 units in PO Al O 3 B O 3 glss ntwork (Ahm t l 1998; Khlif t l 1998). With th introution of rr rth oxis into th ntwork, th intnsity Y (0.1 G P) Er Dy T Sm Pr Y Ho N η ( 0.1 G P) 3000 V m, m/s Tmprtur, o C Figur 4. Vrition of 1. Young s moulus, Y n. rigiity moulus, η with tmprtur of th rr-rth op PO Al O 3 B O 3 glsss Atomi no. Z Figur 6. Mn vloity (V m ) isothrms s funtions of tomi no. Z of rr-rth opnts in PO Al O 3 B O 3 glsss t. 30,. 60,. 100,. 140 n. 180 C θ D(K) H m ( J) Atomi no. Z Figur 5. Isothrms of Dy tmprtur s funtions of tomi no. Z of rr-rth opnts in PO Al O 3 B O 3 glsss t. 30,. 60,. 100,. 140 n. 180 C Atomi no.z Figur 7. Ltnt ht of mlting ( H m ) isothrms o s funtions of tomi no. Z of rr-rth opnts in PO Al O 3 B O 3 glsss t. 30,. 60,. 100,. 10 n. 180 C.

5 Aousti invstigtions on PO Al O 3 B O 3 glsss 67 of th son group of ns slowly inrs n shift towrs slightly lowr frqunis with inrs in th tomi numr, Z, of th rr rth ion. Furthr, luminium n lso oupy oth ttrhrl (viz. sustitutionl or ntwork formrs) n othrl sits (viz. intrstitil or ntwork moifirs) s (Elliott 1990): 3 O3 [Al ] o 3[AlO4/ ] t Al + +. In lumino ort glsss, h BO 4 or AlO 4 unit is link to two suh othr units n on oxygn from h unit with mtl ion n this strutur ls to formtion of long hin of ttrhr. Ln O 3 lso ntrs th glss ntwork s moifir (Shly 1994) y rking up ttrhrl ons (th oxygn of Ln O 3 rk th lol symmtry whil Ln 3+ ion oupy intrstitil position) n introus oorint fts known s ngling ons in ths glsss. During this pross thr n rk of iffrnt struturl units viz. BO 4, PO 4 n AlO 4 units. Th rution in th BO 4 n PO 4 units my unrstoo y th osrv rsing trn of intnsitis of ns orrsponing to ths units in th IR sptr of Diffusion onstnt, D i (10-9, m s -1 ) Atomi no.z Figur 8. Diffusion onstnt (D i ) isothrms s funtions of tomi no. Z of rr-rth opnts in PO Al O 3 B O 3 glsss t. 30,. 60,. 100,. 10 n. 180 C. Trnsmittn % Wvnumr m -1 Figur 9. Infrr sptr of PO Al O 3 B O 3 glsss op with. Pr 3+,. N 3+,. T 3+ n. Y 3+ ions. 650 ths glsss with rsing tomi numr (from Y to Pr) of rr rth ions (figur 9). Furthr ths oning fts giv ris to ltron stts within th n gp of th mtril n gt loliz in tht rgion. Consiring th t on intrnl frition of ths glsss, w hv osrv tht thr is rs in th logrithmi rmnt or offiint of intrnl frition t fix tmprtur (figur ) with rs in th ioni rius (or with inrs in th tomi numr) of th rr rth opnt (from Pr 3+ to Y 3+ ); this is pprntly u to th sussiv rs in th polymriztion of th glss ntwork s lso osrv in IR sptr. This is furthr onfirm y slight inrs in th mirohrnss, H of th PO Al O 3 B O 3 : Ln 3+ glsss with inrs in th tomi numr, Z, of Ln 3+ ions (tl ). Rollting th t on lsti/ousti prmtrs of ths glsss n inrs in th vlus of ths prmtrs viz. V m, Y, η, hs n osrv s w go from Pr 3+ op glsss to Y 3+ op glsss. Th thrmoynmi prmtrs viz. Dy tmprtur, θ D, iffusion onstnt, D i n th ltnt ht of mlting, H m, show similr inrs. In th sris of rr rth ions from L 3+ to Lu 3+ gnrl rs in siz with inrs in tomi numr rsults, us ition of ltrons to th shil 4f oritl nnot ompnst for th fft of inrs nulr hrg. This rs in gnrl is known s lnthni ontrtion. Suh rs in siz from Pr 3+ to Y 3+ uss rs in th gr of polymriztion of PO Al O 3 B O 3 glss ntwork; this is lso orn out y th ft tht th vlus of N[E F ] i.. nsity of loliz ft stts, vlut using.. onutivity vlus t 1 MHz n 303 K (Ngswr Ro n Tl 3. Dt on oustil proprtis of rr rth ions op PO Al O 3 B O 3 glsss. Glss tmp ( C) V m (m/s) θ D (K) Z i 10 6 (kg m s 1 ) H m (J) D i 10 9 (m s 1 ) Pr N Sm Eu T Dy Ho Er Y

6 68 M Rmi Ry, S Bngru Rju n N Vrih Vrih 000), r foun to rs with rs in th ioni rius of rr rth opnts (tl 1). In gnrl, in lss isorr glss frmwork th nrgy introu y th virtor is istriut mor rpily mong th virtionl grs of from of th glss frmwork. Th tim rquir for th stlishmnt of quilirium istriution of nrgy gos on rsing in omprison with th prio of osilltion of th virtor n hn rs in th mhnil loss ftor or offiint of intrnl frition ling to n inrs in th lsti offiints of ths glsss (with rs in th ioni rius of rr rth opnts) is osrv in th prsnt msurmnts. Inrs in th tmprtur of th msurmnt uss n nhnmnt of th polymriztion of th glss ntwork ling to n inrs in th mhnil loss ftor; suh n inrs in th loss ftor my rsponsil for rs in th vlus of V m, Y, η, σ, D i, t with tmprtur for ths glsss. Finlly, our stuy on vrious lsti/ousti proprtis of PO Al O 3 B O 3 : Ln 3+ glsss inits tht PO Al O 3 B O 3 glsss sm to mor suitl (s fr s mhnil strngth is onrn) hosts for th ions lik Ho 3+, Er 3+ whih xhiit y sf lsrs (Chiklis t l 1971) rthr thn to th onvntionl lsing ions lik N 3+, sin th prmtrs lik mirohrnss, H n othr lsti prmtrs r foun to th highst for glsss ontining ning ions of th lnthni sris. Rfrns Ahm A A, A Elshfi N n Eltohmy M R 1998 Inin J. Pur & Appl. Phys Chiklis V, Nsmn E P, Folwilr R C, Gu D R, Jnson H P n Linz A 1971 Appl. Phys. Ltt Elliott S R 1990 Physis of morphous mtrils (Essx: Longmnn Sintifi & Thnil) Khlif F A, Elhi A A, Al-Kshn A n Mustf F A 1996 Inin J. Pur & Appl. Phys Khlif F A, Bhtl H A El n Azooz A 1998 Inin J. Pur & Appl. Phys Kumr A R n Vrih N 1999 J. Mtr. Si. Ltt Ll M n Singh D P 1993 Inin J. Phys. A Mllwny R El 1994 Mtr. Chm. Phys Nhimuttu P n Jgnnthn R 1995 Phys. Chm. Glsss Ngswr Ro K n Vrih N 000 Inin J. Phys. A74 37 Rmi Ry M, Bngru Rju S n Vrih N 000 Phys. Chm. Solis Rvikumr V n Vrih N 1997 Bull. Mtr. Si Stynryn J V n Buhuu S 1994 Alloys & Compouns Shly J E 1994 Ky Eng. Mtr Singh Knwrjit, Singh D P n Bhtti S S 199 J. Pur Appl. Ultrsonis 14 56