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(AgI)x(Ag2S·GeS2)1−x glasses studied by 109Ag NMR
~lld State]cams28-30 (198g)710-712 N~h.HoIland,~ s ~ d a m
(Ael).(A~S-GeS~h~ G I . ~ S E S S t O r I E D BY Z~Ag ~ M R J. ROOS, D. [iRINKMAN~, M. MALl
A, PRADEL and M. PdBES Re~ci~d4 A~gust19~7 The''Ag ~i.-W~n ,nO n0~lan;~r r ~im~forx=0.375a.d x=c~n~a~eb~. m e a m ~ i , ard=lO elucidateme~ ,liff..~,d~ ami=.T~e~ l t * a~ ~ i s l e , t withthefa:tthat ther ~ *ith in--singx a.d thatthe O~S,g~a.e, IheNMRtimesteleaUionsa~ mobile~r~+fi.c~nea~mes thaithe Agions" h ~ " f~m ouei~inr
to $ , o1~r
1. Introduction
o t h e ~ i s e e• data would be irreprodur b]e during tempcratu~ c'~[ing. The detailed mechanismo f the Ag diffusionin Agl The '~ NMR experiments w e n p e f f o ~ e d i n a based superi~ie glasses is still a ~ t t e r o f debate, super~nducfingmagneto f 5.17 T fieldstrength~ Whatever the glassis,the ~ ~ n d u e l i v t i ylimito f ~sponding to a speclrometer frequency o f ~/2~ about I ( n m ) - ' is obtained for the h i g h ~ tAgI ~ n = [0.2 MTdz, The f r ~ i n d u e t l n nd e ~ y (FID) ~ d tent.AnOlmnquestinni~whethero~lytbcsilverlons spin-echo signals were digitized by t~naient r ~ a ~ c i a l e d with the iodide i~ns a ~ mobile and c o r d ~ , accumulatedand then Fourier t r a n s p o s e d whethermicrodomainso f p ~ Agl a~e f o ~ e d within by a n on-fine compuler. The spin-latticerelaxation the glass n e t ~ r k . In an attempt to a n~r~f at I~st t i m ~ TI ~ obtainedfromthe FID signalusingthe some o f t h ~ que~tion~ ~ have slarled an inveslieonv~tiona[ x - - h i 2 p u l ~ s e q u e n t . The spin-spln gation of (Agl)~(AgzS-ne~),_. g l a m ~ in a fashion ~laxationtime T~was deduced f ~ m the echo slgnal similar ~o our p~vious sludy of which follows a n/2--~ pulse sequ~ce. (Agl)x(Ag202B20)),-x g l ~ e s I l l , Here we are repo~hag p~limma~y~sult~. 3, RelaxaOoa times 2. E~perlmental m ~ l t $ The ~mgies h a ~ ~ prepared a t detcnbed p~viously {2], The mamrials were e~ahed and the powders w e n put imp pyrex tubes whichw~r scale4 under vacuum to pmvenl o~idlzationat high ternp e ~ t u * , To ~ 1 ~ the strain produced during quenching,~he ~ m p ] ~ ~ e annezded for about 12 h at 50 K below the glass transition temperatu~,
Fig, 1 si~oss*the temperer urr d o p ~ d e n ~ o f the sgia*latt i ~ ~ l = a t i o n rate IIT~ o f the g l l v ~ imtope '~Ag for two values o f ~ ~Vnetime constant T, meammsthemteatwhichtheAgspinsyst~ehes t h ~ a l equilibriumwith the "lattice".The ov~al] behavior o f the present data is quite similarto that o f the e a ~ s p n n d i n g borate g i ~ s and the maxim u m ~ l u c s o f the rates a ~ nearlythe ~ m e [ I ]. In both cases the ~laxatlonarlses from fluctuationso f
0 1bT-2738/gg/$ 03.50 9 Elsevier$cien~ Publishc~ B.V. (North-Holland Physics PublishingDivision)
in both low- [4] ~ d ~]atively h l g h ~ n d o c t i ~ [5] 1
~ "
005r~
-~-~-o~stse%:%~:o~*,0 ~ 4 6
~
"'i", 3 17
~000/T [K~] ~ g i Tcmpmtu~ de~n~tn~ oflhe a ~ nin Tatti~ nTmxa. tio~ rote The5ion am ~ i a a to th r r the zni~troplr ehemiml shin experienced b y the Ag nuclei due to Ag m~ements, In ~ a t r a s t to Ag in ~ vocal ctystalLine superionic condneto~ [3], hoover, the rr ~nnot be descnbed b y the simple Bl~mbergen-PdrcellPound (BPP) f ~ u l a
I/TI=A2ZI(I+o~r ~) (I) its modifi~tions. Here, A ~ d r are amplitude ~ d ~ n e l a t i o n time, ~spectively, o f the fluctuatingloca] field at tJte Ag site, a n d one usually identifies t with the m ~ n ~ s l d e n ~ time of an Ag ion. Toe departure from the BPP behavior in fig. 1 is obvious from the asymmetry o f the data set wilh ~spect to the ternpemture w h e ~ the I/T~ maximum ~ u ~ , This statement applies also to 1he previous Ag relaxation behavior in the borate gl~ses [ 1 ] as has been ~ vealed by reinsp~tio~ of our aid data. Also not ~lis fying is an analysis of the ruination data by usit~ a Cole-Do vldson dist fibntion P(r) t'or the c o ~ l a t i o n tim as. TMs 0J stt~ut ion is defined by P(*) = (1/~) t i n a ~ [~1(~*-r)] ~ . t ribnlion ~ d a is a width parameter. T h e ~laxalion rate is lhe~ nblak-~ed by a n imegradon over a~l z vaIues:
IITI
=(J P(z)[tl(I +m~t~)] d r
This negative result is surprising s i n ~ the CO[~ Davidson a~lysis has I~-~n quite sa~essfn[ in explaining N M R rel~ation in other g]asscs,and that
t l ~ l a r r e l a t i o n m~ilaoism of the AB nuolel (ani~liopir chemi6al shift) and/or ~ m c other ~ u n are r~ponsible for the "failu~". F r ~ the slope of the r e l a t i o n ~ l e e u ~ on the I~-tcmpcrature side o f the ~ x i m a m one ~ l ~ l a l e s " a p p a ~ o t aeti~tion energy" of 0.08 and 0 07 eV for x=0.375 ~ d x=0,5, ~spr165 H. . . . . . . . . long as a ~ t i s f a ~ o ~ desetiptlon of the ~ h x a t l o n is not at h ~ d , it is n m meaningful Io ~ m p a r e t h e ~ energies ~ith the values 029 and 027 eV oblained in conductivity m ~ s u r ~ e n t * [2]. R ~ r ~ r o f the e o ~ t de~ription ~ f the ~ ] = arian totes, th e rate m*xlmum must o c ~ r at a ternperat are w h e ~ me is of" the ardor L S I n ~ in the x = 0 . 5 sample the ~ i m u m is ~aehed at a lower temperata~ than in the sampM xfO.375, the therreally activated ]/~ must be larger for x=O.~ (at e q ~ l temp~atures). In other words, a higher AgI content should i n c ~ a ~ the condncti~4t3, e ~ obe y e d experimentally [2]. The ~ m e t~deney has been found in the borate glasses [ 1 ]. H o ~ e r , for the ~ m e x value, the Ag movements in the p ~ t GaS2 g l ~ s are fast~ than in the B2Oa glam~ a n d one e x p e l s a better conductivity in the ~ m ~ - in agreement with conductivity measu~mcnts [ 2 ]. F i g 2 s h o ~ the t m p e m t u r e dependen~ of the raJ~atioa rate lIT2. ~ae spin-spin ~laxat ban time
T2isam~surcf~176 tern to reach i a t ~ a [ equilibrium. AS ale:rely noted for the T~ data, t h e ~ is also a large simi!artty bet w i n the p n ~ t 1"2d a ~ a n d t h o ~ of the b a n t u glasses [ 6], In the bo~te glasses I/T~ is a l ~ larger for the s ~ M l ~ x value a n d the rites ~ c h their peak values ~ about [0~ s-I at ab~ 250 K F~ both tYP~ o f 81m~s we note that 7"2is smaller t h ~ T, by some orde~ of magnitude. 4. Estimate of ~ b i l e i ~ concentration w ~ ~a~t to estimate t~e c o n ~ z m t l o ~ mobile Ag ions. By combining the Ein~ein D=
a=(r~>q~ed(6~kl.).
n u r the e~i~tlon equation ~ lo the (2)
~7 SC~
~
the number of mobileions is to use the Nemst-Einste~n m l a t i ~ alone ~ d to measure D (by 1he NIdR PFG m~hod) and ~ on the ~ s a m e ~mple. "Ihls has re~Rtly been done [7] for the borate based # ~ c s (Agi)~6~(AgaO'2B203)oaswiththe ~ t t t t that ~ u g h l yall Ag iota ~ mobile. Corresponding menaugments for the sulfidebased g l ~ s aM f ~ s i h l e above say 370 K whom T2 is large enough {fig2) to
........
/,:
allowthe applicationoflhc P F G method. Thiswork ~sin p r ~ Our ~ l i m a t e for the sulfideand the result For the borate g I ~ ~ n t m s t sharply with the wink electrolytetheory [ 8 ] whichh ) ~ O t h e s i ~ that an ion b e longing to the ~ n d u c t i n g species ~ n tm either "dissociated"and mobile or " a s ~ i ~ m d " and immobile. Howcv~, i f the lifetimeo f the a ~ c i a t e d slate is short ~ m p a ~ d to the NMR time~ 1 ~ which a ~ either Tt i n the ~ o f r e l a t i o n stndles t o f the order o f I s) or T~ i n the ~ o f the PFG m ~ s a ~ ; ~ l S (0.01 s) then from the NMR '*point o f view" all i ~ s a ~ mobile.
~] teOO/T [~"l
Hem, q ~ d (r~) ~e charge~ d mean squarej ~ p dlstan~,respectively,of tim mobileAg inns.For the x=O.5 ~ m p l e we know both ( i ) the Ag j u m p fie. qneaey l / z because ~fthr e0ndifion~ ~ 1 validfor the l i T , mazh~num at 286 K~ and (ii) the expsrimental value a~0.2g ( n m ) - ' [2]. Thus eq. (2)
References
yields
W.gS~)49. [31 H, Lo~r, D. Bdnkma~u,M, t~talia~d ). t t ~ SOI,dSta,e to~i~ S 09Sl~ 4S~, [4] ~ G ~ L W. M~B~.Wa~othandH. OIyschl~er.J. ~ a ~
n ( # ) =4.0xlO~ m - ' .
(3)
w e assume now [21 thatAg ions simply hop from one iodineion to ~otber, tho~ ionsbeing5.8 A a m r t on the average i f the ~ndlne distributionis isotropic. Then we get from eq. (3) n ~ l . 2 X l 0 zs m ~, that means thalesscntiaUyall Ag i~ s a~ mobile.Within the f r ~ e ~ r k of oar ~ssumptions this ~lJmate is true on the N M R tlme sca~ewhich is mughl)'defmed by the m ~ i l u d e of T~. Ofnan~e, the more uonvlncin$way to d~ermine
[tls,w. Mamn, n J . ai~uf, M. M~li, J. R~s ~n~ D. Brinkman~.~lid S~te lonlcs18r (1986)421,
[ 51J. SeneCaandL Olios-Fondu,J. Phy~Cn~. Solid~**
[71 J. Rom,un0ublishedresult~ i8] ~ RavMnea ~ J,L ~ u q ~ Phys,C ~
G ~ s 1g {1977)
(Ael).(A~S-GeS~h~ G I . ~ S E S S t O r I E D BY Z~Ag ~ M R J. ROOS, D. [iRINKMAN~, M. MALl
A, PRADEL and M. PdBES Re~ci~d4 A~gust19~7 The''Ag ~i.-W~n ,nO n0~lan;~r r ~im~forx=0.375a.d x=c~n~a~eb~. m e a m ~ i , ard=lO elucidateme~ ,liff..~,d~ ami=.T~e~ l t * a~ ~ i s l e , t withthefa:tthat ther ~ *ith in--singx a.d thatthe O~S,g~a.e, IheNMRtimesteleaUionsa~ mobile~r~+fi.c~nea~mes thaithe Agions" h ~ " f~m ouei~inr
to $ , o1~r
1. Introduction
o t h e ~ i s e e• data would be irreprodur b]e during tempcratu~ c'~[ing. The detailed mechanismo f the Ag diffusionin Agl The '~ NMR experiments w e n p e f f o ~ e d i n a based superi~ie glasses is still a ~ t t e r o f debate, super~nducfingmagneto f 5.17 T fieldstrength~ Whatever the glassis,the ~ ~ n d u e l i v t i ylimito f ~sponding to a speclrometer frequency o f ~/2~ about I ( n m ) - ' is obtained for the h i g h ~ tAgI ~ n = [0.2 MTdz, The f r ~ i n d u e t l n nd e ~ y (FID) ~ d tent.AnOlmnquestinni~whethero~lytbcsilverlons spin-echo signals were digitized by t~naient r ~ a ~ c i a l e d with the iodide i~ns a ~ mobile and c o r d ~ , accumulatedand then Fourier t r a n s p o s e d whethermicrodomainso f p ~ Agl a~e f o ~ e d within by a n on-fine compuler. The spin-latticerelaxation the glass n e t ~ r k . In an attempt to a n~r~f at I~st t i m ~ TI ~ obtainedfromthe FID signalusingthe some o f t h ~ que~tion~ ~ have slarled an inveslieonv~tiona[ x - - h i 2 p u l ~ s e q u e n t . The spin-spln gation of (Agl)~(AgzS-ne~),_. g l a m ~ in a fashion ~laxationtime T~was deduced f ~ m the echo slgnal similar ~o our p~vious sludy of which follows a n/2--~ pulse sequ~ce. (Agl)x(Ag202B20)),-x g l ~ e s I l l , Here we are repo~hag p~limma~y~sult~. 3, RelaxaOoa times 2. E~perlmental m ~ l t $ The ~mgies h a ~ ~ prepared a t detcnbed p~viously {2], The mamrials were e~ahed and the powders w e n put imp pyrex tubes whichw~r scale4 under vacuum to pmvenl o~idlzationat high ternp e ~ t u * , To ~ 1 ~ the strain produced during quenching,~he ~ m p ] ~ ~ e annezded for about 12 h at 50 K below the glass transition temperatu~,
Fig, 1 si~oss*the temperer urr d o p ~ d e n ~ o f the sgia*latt i ~ ~ l = a t i o n rate IIT~ o f the g l l v ~ imtope '~Ag for two values o f ~ ~Vnetime constant T, meammsthemteatwhichtheAgspinsyst~ehes t h ~ a l equilibriumwith the "lattice".The ov~al] behavior o f the present data is quite similarto that o f the e a ~ s p n n d i n g borate g i ~ s and the maxim u m ~ l u c s o f the rates a ~ nearlythe ~ m e [ I ]. In both cases the ~laxatlonarlses from fluctuationso f
0 1bT-2738/gg/$ 03.50 9 Elsevier$cien~ Publishc~ B.V. (North-Holland Physics PublishingDivision)
in both low- [4] ~ d ~]atively h l g h ~ n d o c t i ~ [5] 1
~ "
005r~
-~-~-o~stse%:%~:o~*,0 ~ 4 6
~
"'i", 3 17
~000/T [K~] ~ g i Tcmpmtu~ de~n~tn~ oflhe a ~ nin Tatti~ nTmxa. tio~ rote The5ion am ~ i a a to th r r the zni~troplr ehemiml shin experienced b y the Ag nuclei due to Ag m~ements, In ~ a t r a s t to Ag in ~ vocal ctystalLine superionic condneto~ [3], hoover, the rr ~nnot be descnbed b y the simple Bl~mbergen-PdrcellPound (BPP) f ~ u l a
I/TI=A2ZI(I+o~r ~) (I) its modifi~tions. Here, A ~ d r are amplitude ~ d ~ n e l a t i o n time, ~spectively, o f the fluctuatingloca] field at tJte Ag site, a n d one usually identifies t with the m ~ n ~ s l d e n ~ time of an Ag ion. Toe departure from the BPP behavior in fig. 1 is obvious from the asymmetry o f the data set wilh ~spect to the ternpemture w h e ~ the I/T~ maximum ~ u ~ , This statement applies also to 1he previous Ag relaxation behavior in the borate gl~ses [ 1 ] as has been ~ vealed by reinsp~tio~ of our aid data. Also not ~lis fying is an analysis of the ruination data by usit~ a Cole-Do vldson dist fibntion P(r) t'or the c o ~ l a t i o n tim as. TMs 0J stt~ut ion is defined by P(*) = (1/~) t i n a ~ [~1(~*-r)] ~ . t ribnlion ~ d a is a width parameter. T h e ~laxalion rate is lhe~ nblak-~ed by a n imegradon over a~l z vaIues:
IITI
=(J P(z)[tl(I +m~t~)] d r
This negative result is surprising s i n ~ the CO[~ Davidson a~lysis has I~-~n quite sa~essfn[ in explaining N M R rel~ation in other g]asscs,and that
t l ~ l a r r e l a t i o n m~ilaoism of the AB nuolel (ani~liopir chemi6al shift) and/or ~ m c other ~ u n are r~ponsible for the "failu~". F r ~ the slope of the r e l a t i o n ~ l e e u ~ on the I~-tcmpcrature side o f the ~ x i m a m one ~ l ~ l a l e s " a p p a ~ o t aeti~tion energy" of 0.08 and 0 07 eV for x=0.375 ~ d x=0,5, ~spr165 H. . . . . . . . . long as a ~ t i s f a ~ o ~ desetiptlon of the ~ h x a t l o n is not at h ~ d , it is n m meaningful Io ~ m p a r e t h e ~ energies ~ith the values 029 and 027 eV oblained in conductivity m ~ s u r ~ e n t * [2]. R ~ r ~ r o f the e o ~ t de~ription ~ f the ~ ] = arian totes, th e rate m*xlmum must o c ~ r at a ternperat are w h e ~ me is of" the ardor L S I n ~ in the x = 0 . 5 sample the ~ i m u m is ~aehed at a lower temperata~ than in the sampM xfO.375, the therreally activated ]/~ must be larger for x=O.~ (at e q ~ l temp~atures). In other words, a higher AgI content should i n c ~ a ~ the condncti~4t3, e ~ obe y e d experimentally [2]. The ~ m e t~deney has been found in the borate glasses [ 1 ]. H o ~ e r , for the ~ m e x value, the Ag movements in the p ~ t GaS2 g l ~ s are fast~ than in the B2Oa glam~ a n d one e x p e l s a better conductivity in the ~ m ~ - in agreement with conductivity measu~mcnts [ 2 ]. F i g 2 s h o ~ the t m p e m t u r e dependen~ of the raJ~atioa rate lIT2. ~ae spin-spin ~laxat ban time
T2isam~surcf~176 tern to reach i a t ~ a [ equilibrium. AS ale:rely noted for the T~ data, t h e ~ is also a large simi!artty bet w i n the p n ~ t 1"2d a ~ a n d t h o ~ of the b a n t u glasses [ 6], In the bo~te glasses I/T~ is a l ~ larger for the s ~ M l ~ x value a n d the rites ~ c h their peak values ~ about [0~ s-I at ab~ 250 K F~ both tYP~ o f 81m~s we note that 7"2is smaller t h ~ T, by some orde~ of magnitude. 4. Estimate of ~ b i l e i ~ concentration w ~ ~a~t to estimate t~e c o n ~ z m t l o ~ mobile Ag ions. By combining the Ein~ein D=
a=(r~>q~ed(6~kl.).
n u r the e~i~tlon equation ~ lo the (2)
~7 SC~
~
the number of mobileions is to use the Nemst-Einste~n m l a t i ~ alone ~ d to measure D (by 1he NIdR PFG m~hod) and ~ on the ~ s a m e ~mple. "Ihls has re~Rtly been done [7] for the borate based # ~ c s (Agi)~6~(AgaO'2B203)oaswiththe ~ t t t t that ~ u g h l yall Ag iota ~ mobile. Corresponding menaugments for the sulfidebased g l ~ s aM f ~ s i h l e above say 370 K whom T2 is large enough {fig2) to
........
/,:
allowthe applicationoflhc P F G method. Thiswork ~sin p r ~ Our ~ l i m a t e for the sulfideand the result For the borate g I ~ ~ n t m s t sharply with the wink electrolytetheory [ 8 ] whichh ) ~ O t h e s i ~ that an ion b e longing to the ~ n d u c t i n g species ~ n tm either "dissociated"and mobile or " a s ~ i ~ m d " and immobile. Howcv~, i f the lifetimeo f the a ~ c i a t e d slate is short ~ m p a ~ d to the NMR time~ 1 ~ which a ~ either Tt i n the ~ o f r e l a t i o n stndles t o f the order o f I s) or T~ i n the ~ o f the PFG m ~ s a ~ ; ~ l S (0.01 s) then from the NMR '*point o f view" all i ~ s a ~ mobile.
~] teOO/T [~"l
Hem, q ~ d (r~) ~e charge~ d mean squarej ~ p dlstan~,respectively,of tim mobileAg inns.For the x=O.5 ~ m p l e we know both ( i ) the Ag j u m p fie. qneaey l / z because ~fthr e0ndifion~ ~ 1 validfor the l i T , mazh~num at 286 K~ and (ii) the expsrimental value a~0.2g ( n m ) - ' [2]. Thus eq. (2)
References
yields
W.gS~)49. [31 H, Lo~r, D. Bdnkma~u,M, t~talia~d ). t t ~ SOI,dSta,e to~i~ S 09Sl~ 4S~, [4] ~ G ~ L W. M~B~.Wa~othandH. OIyschl~er.J. ~ a ~
n ( # ) =4.0xlO~ m - ' .
(3)
w e assume now [21 thatAg ions simply hop from one iodineion to ~otber, tho~ ionsbeing5.8 A a m r t on the average i f the ~ndlne distributionis isotropic. Then we get from eq. (3) n ~ l . 2 X l 0 zs m ~, that means thalesscntiaUyall Ag i~ s a~ mobile.Within the f r ~ e ~ r k of oar ~ssumptions this ~lJmate is true on the N M R tlme sca~ewhich is mughl)'defmed by the m ~ i l u d e of T~. Ofnan~e, the more uonvlncin$way to d~ermine
[tls,w. Mamn, n J . ai~uf, M. M~li, J. R~s ~n~ D. Brinkman~.~lid S~te lonlcs18r (1986)421,
[ 51J. SeneCaandL Olios-Fondu,J. Phy~Cn~. Solid~**
[71 J. Rom,un0ublishedresult~ i8] ~ RavMnea ~ J,L ~ u q ~ Phys,C ~
G ~ s 1g {1977)