Diffraction studies of the structural phase transition in the high temperature superconductor YBCO

Khoshnevisan, B

Abstract

In-situ x-ray and neutron, diffraction combined with computation modelling have been used to elucidate the details of the structural phase transitions in TBa2Cu3O,
6+,
c
for
)f
0<, X<I.
in this study it is found that in the elevated temperature
range
[200
-
306P
C],
with
increasing oVgen content, the structure changesfrom the
weff
known tetragonaf
(Tet. )
to the orthorhom6ic Il (01I) superfattice phase
(under thermodynamical
equi(Wrium
condition) 9fii; transition is found to
6e first
order
(a
matter of
considera6fe
controversy) with the eApectedlinear change
in the
volume
action
ofeach
phase across
fir
the corresponding two phase mked rcgion
(Gi66s
phase rure)
qfie
possi6ifilty of the
e*tence of a sta6re entirery Oll phase region at
30OPC
arvundxý-,
a 7 is
perhaps the
most nota6fe resuft of this study, which this resuft
implies
a substantialcorrection
on
the TBCO's structura[phase diqrnn Trom thefuff
anafyses of the
data, the
possi6ifity
of theformation of a superstructure arong the
'c' direction
under the
aforementioned
conditions cannot 6e ruledout
-At
hýqher temperature [500
-
600*Cj the measurements
rer4te to the
secondorder
Tet. to
otthorhom6ic 1 (01) phase transidom qfie interesting issue
here is the
nature of the
twining mirrostructure thatformsJust after the transition.
-2'fie
computation
modeling
and peak 6roadening anafyses of the data, reveafs the interference
effect on the
dif'fracted peak shapes from the thin stripe twinned
sampfe at the
eady stages
of
transitionfrom the Tet. to OIphase

Citation

Khoshnevisan, B. Diffraction studies of the structural phase transition in the high temperature superconductor YBCO. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Sep 22, 2011
• Publicly Available Date: Sep 22, 2011
• Award Date: Jan 1, 2002