vidrio

1. PhysicaC 162-164 (1989) 1289-1290
North-Holland
EPR ON Y-CERAMICSAND Bi-VITROCERAMICSDOPED WITH S STATE PARAMAGNETICIONS
Simion SIMON, Gheorghe ILONCA, loan BARBUR, loan ARDELEAN, Radu REDAC*
PhysicsDepartment, Universityof Cluj-Napoca,Romania; * ICSITMU- Arad, Romania
The effect of Gd doping and of thermal history on the EPR spectra from Yl.xGdxBa2Cu307.~ ceramicsand, for the first
time, from Bi2_xGdxSr2Ca20z vitroceramics was investigated. The results were correlated with the superconducting
properties of the studied samples.
INTRODUCTION
In the systenw oontaAning no other
paramognetio ions than the ooppe~ ones,
the EPR signals arise from Cu2+disposed
An non-superoonduoting imptueit¥ phases.
In most systems investigated by EI~ the
ytrium was substituted by gadolinium 1'2
beoause the last one may bring informa-
tion about the ooexietenee of these
ions with the superoonduoting phase.
EXPERIMENTAL
The Yl_xOd~a20u307_ ~ oeramie samplell,
with O~.x~I, were prepax,ed from ¥203,
Gd203, RICO 3 and Otto mlxt~L1~ oeloinatod
st 900°C for 16 h (samples noted Gd°)
and slnte~ized in o~gen flow at 93000
in "two stages: fo~ 10 h with 5°C/sin
ooolAng to room temperature (Gd~ 1 sam-
ples) end fo~ other 8 h with 3oC/md-
ooolAng and 1 h tempemtuA~ shoulder st
50000 (Gd~2 samples). Some Gd~2 samples
were further heated An air St 930°C and
IOOOOC respeotively and quenohed into
liquid nitrogen (Gdql and Gdq2 samples
mspeotively) •
The B2_xOdxSr20a20u30 z vltroee~amies,
with 05x~0.3 we~e obtained by pi.~tlal
o~ystallization st 84000 up to 20 h of
glasses p~epa~ed at 120000 from 21203,
Gd203, SrC03, CeO03 and CuO mixtures.
0921-4534/89/$03.50 © Elsevier Science Publishers B.V.
(North-Holland)
The SPR speotm were ~eoorded on I
standard JEOL speotromtar An • bind,
at room tempeA~tuA~, on powder samples.
The do susoeptibility lasu~emonta were
~rried out by mei~s Of I st~l~rd Fi-
reclay balonoo and an applied field of
7.5 KG.
RESULTS AND DISCUSSION
¥1_xGd~a2Cu307_ 8 samples exhibit
after oaloination s ~elatively iyI-
trleal Qd3+ EPR siIIil with geff-2oO
The linewidth AnOrSaISI 1Anesi:l~ Wi~h
Gd203 oontant (fiE.l). In these samples
~HIGI
~200
1000
800
600
40C /'-J/ , a<t,"
1 I I I I-
0.2 O.~. 0.6 0.8 1X
Y IGURE 1
EPR linewidth depend.nee on Gd20~ son-
tent An Yl_xGdXBa2gu307_ 8 samples.
was not obsezved the Ou2+ signal. The
Od~l samples pJ~esent belch Od3* and 0u 2+

2. 1290 S. Simon et al. / EPR on Y-ceramics and Bt-vitroceramics
eipk, but the Cu2+ one disappears by
further einteri-~, so that it is not
observed at the Gd~2 samples.
The •intarin~ determ4,mtas • narro-
wing of the QdJ+ ~PR lines because the
mtoroenvtronment• of Gd3+ ions •x.s uni-
fo~mis•d and at the same time the su-
peroenduoting pha•• develops. Th• Gdql
• ample• pro•ant a o•nsiderobla broade-
ning of the resonano• line. Th• eff•ot
i• more prenounoed for Gdq2 samples.
Th• Gdq2 ••mple• are not superoonduo-
tiv• at T> 80 K.
Th• Bi2_xGdxSr2Os2Gu30 m glass •am-
plea exhibit BPR spoetra re•ultad from
• uperpositian of • oymmetrleal signal
with ~eolved hyperflne structure,
typical of Ou2+ ion8 disposed in •ires
of axial synnstl-y3 , with 8 large dls-
tribution of the spin Htmiltonlan pelf•-
meters and a elgn81 speolflo to Gd3+
ions from vitreous mortises 4 whose
sha~e inorsase• with Gd203 oontent.
These sample• do not exhibit •uperoon-
dusting phase above 80 K.
The susceptibility measurements e-
videnced a perama~tic behaviou~ of
the samples 5 and allowed an estt-~tlon
of gu 2+ ions from the total number of
sapper ions (table 1). We have took for
Gd ions (8S7/2) Otuele son•rant 7.9
emu/mol and for Cu2+ ions 0.3745
emu/mol.
Table i. Experimental molar Our~e
oonstanta (OM) and ratio (r) of Ouz+
ions to total numbeE of sapper ions in
vitreous Bl2_xGdxSr20a2Ou30 z sample•.
~: if= (emu/mol) r ~)
o.o1 o. 4167 3o.ob
0.05 0.7204 28.96
0.075 0.6861 8.33
0.10 0.893 9.17
0.15 1.2925 9.57
O.20 1.8348 22.97
0.25 2.323 30.97
0.30 2.182 36.67
The partial o~ystallization of the
samples determine• important ohange• in
shape and parameter• of EPR spectra il-
lustrat•d in flgu~e 2 for x=O.03. The
~e•ults suggest pronounoed ohan&~s of
the looal ord•~ of Cu2+ and Gd3+ ions
2O00 2500GS
I':lOh
f
FIGURE 2
H•at treatment •ff•ot on EPR speotra
of Bil.97Gd0.o3Sr20a20u30s sampl•.
and of the interactions between them.
These modifioa~lons may be oorrolat•d
with the dev•lopment of superoonduoting
pha•• with To > 80 K.
REFERENOES
l.F.Meh~am et al.,l~Ts.Rev.56B(198~7266
2.A.Doville •t al, F~Ts.155 C(1988)669
3.H.Imagswe, Phys.St.Sol. 30 (1968)469
4.J.T.Lue, l~ys.Rov. 38B (1988) 4592
5.S.81mon •t al., Studia Phys.,in pEin~