Synchrotron X-ray powder diffraction study of the tetragonal-cubic phase transition in nanostructured ZrO2-Sc2O3 solid solutions

2008 ◽  
Vol 23 (S1) ◽  
pp. S87-S90 ◽  
Author(s):  
Paula M. Abdala ◽  
Diego G. Lamas ◽  
Mária E. Fernández de Rapp ◽  
Noemí E. Walsöe de Reca ◽  
Aldo F. Craievich ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Average Crystallite Size ◽  
Cubic Phase ◽  
X Ray ◽  
Cubic Phases ◽  
Gel Combustion ◽  
Combustion Route

The transition between tetragonal and cubic phases in nanostructured ZrO2-Sc2O3 solid solutions by high-temperature X-ray powder diffraction using synchrotron radiation is presented. ZrO2-8 and 11 mol% Sc2O3 nanopowders that exhibit the t′- and t″-forms of the tetragonal phase, respectively, were synthesized by a stoichiometric nitrate-lysine gel-combustion route. The average crystallite size treated at 900°C was about 25 nm for both compositions. Our results showed that t′-t″ and t″-cubic transitions take place for the 8 and 11 mol% Sc2O3 samples, respectively.

High-temperature X-ray powder diffraction study of the tetragonal-cubic phase transition in nanocrystalline, compositionally homogeneous ZrO2–CeO2 solid solutions

2008 ◽  
Vol 23 (S1) ◽  
pp. S70-S74 ◽  
Author(s):  
L. M. Acuña ◽  
R. O. Fuentes ◽  
D. G. Lamas ◽  
I. O. Fábregas ◽  
N. E. Walsöe de Reca ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray ◽  
First Order

Crystal structure of compositionally homogeneous, nanocrystalline ZrO2–CeO2 solutions was investigated by X-ray powder diffraction as a function of temperature for compositions between 50 and 65 mol % CeO2. ZrO2-50 and 60 mol % CeO2 solid solutions, which exhibit the t′-form of the tetragonal phase at room temperature, transform into the cubic phase in two steps: t′-to-t″ followed by t″-to-cubic. But the ZrO2-65 mol % CeO2, which exhibits the t″-form, transforms directly to the cubic phase. The results suggest that t′-to-t″ transition is of first order, but t″-to-cubic seems to be of second order.

Powder-diffraction data for several solid solutions with the compositions (CaxSr1−x)CuO2 and (CaxSr1−x)2CuO3

1995 ◽  
Vol 10 (4) ◽  
pp. 296-299 ◽  
Author(s):  
S. T. Misture ◽  
C. Park ◽  
R. L. Snyder ◽  
B. Jobst ◽  
B. Seebacher
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Diffraction Data ◽  
Solid State Reaction ◽  
High Temperature Superconductors ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Diffraction Patterns

Several compositions of the solid solutions (CaxSr1−x)CuO2 and (CaxSr1−x)2CuO3, both of which are found as minor phases in the high-temperature superconductors, were prepared by solid-state reaction. X-ray powder-diffraction patterns for three compositions of (CaxSr1−x)CuO2 and two for (CaxSr1−x)2CuO3 are presented.

High-Temperature Synchrotron X-Ray Powder Diffraction Study of the Orthorhombic–Tetragonal Phase Transition in La0.63(Ti0.92,Nb0.08)O3

2002 ◽  
Vol 164 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Roushown Ali ◽  
Masatomo Yashima ◽  
Masahiko Tanaka ◽  
Hideki Yoshioka ◽  
Takeharu Mori ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Diffraction Study ◽  
Powder Diffraction ◽  
Tetragonal Phase ◽  
X Ray ◽  
Tetragonal Phase Transition

Barium hollandite-type compounds BaxFe2xTi8−2xO16 with x=1.143 and 1.333

1999 ◽  
Vol 14 (1) ◽  
pp. 31-35 ◽  
Author(s):  
J. M. Loezos ◽  
T. A. Vanderah ◽  
A. R. Drews
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Framework Structure ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Diffraction Patterns ◽  
Acta Crystallogr

Experimental X-ray powder diffraction patterns and refined unit cell parameters for two barium hollandite-type compounds, BaxFe2xTi8−2xO16, with x=1.143 and 1.333, are reported here. Compared to the tetragonal parent structure, both compounds exhibit monoclinic distortions that increase with Ba content [Ba1.333Fe2.666Ti5.334O16: a=10.2328(8), b=2.9777(4), c=9.899(1) Å, β=91.04(1)°, V=301.58(5) Å3, Z=1, ρcalc=4.64 g/cc; Ba1.143Fe2.286Ti5.714O16: a=10.1066(6), b=2.9690(3), c=10.064(2) Å, β=90.077(6)°, V=301.98(4) Å3, Z=1, ρcalc=4.48 g/cc]. The X-ray powder patterns for both phases contain a number of broad, weak superlattice peaks attributed to ordering of the Ba2+ ions within the tunnels of the hollandite framework structure. According to the criteria developed by Cheary and Squadrito [Acta Crystallogr. B 45, 205 (1989)], the observed positions of the (0k1)/(1k0) superlattice peaks are consistent with the nominal x-values of both compounds, and the k values calculated from the corresponding d-spacings suggest that the Ba ordering within the tunnels is commensurate for x=1.333 and incommensurate for x=1.143. High-temperature X-ray diffraction data indicate that the x=1.333 compound undergoes a monoclinic→tetragonal phase transition between 310 and 360 °C.

High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3phases

2016 ◽  
Vol 72 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Akira Yoshiasa ◽  
Tomotaka Nakatani ◽  
Akihiko Nakatsuka ◽  
Maki Okube ◽  
Kazumasa Sugiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Single Crystal ◽  
Diffraction Study ◽  
Relative Displacement ◽  
High Temperature Phase ◽  
Cubic Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray

A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3perovskite was carried out over the wide temperature range 298–928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetricP4mmsymmetry group, the difference in relative displacement between Pb and O along thec-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye–Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factorUeqfor O is observed in the vicinity of the transition point, whileUeqvalues for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘDfor Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.

Synchrotron X-ray diffraction study of the tetragonal–cubic phase boundary of nanocrystalline ZrO2–CeO2synthesized by a gel-combustion process

2005 ◽  
Vol 38 (6) ◽  
pp. 867-873 ◽  
Author(s):  
D. G. Lamas ◽  
R. O. Fuentes ◽  
I. O. Fábregas ◽  
M. E. Fernández de Rapp ◽  
G. E. Lascalea ◽  
...  
Keyword(s):  
Phase Boundary ◽  
Solid Solutions ◽  
Tetragonal Phase ◽  
Combustion Process ◽  
Fluorite Structure ◽  
Cubic Phase ◽  
X Ray ◽  
Gel Combustion ◽  
Fluorite Type ◽  
Oxygen Anions

The crystal structures of a number of nanocrystalline ZrO2–CeO2solid solutions, synthesized by a pH-controlled nitrate-glycine gel-combustion process, were studied. By using a synchrotron X-ray diffractometer, small peaks of the tetragonal phase, which correspond to forbidden reflections in the case of a perfect cubic fluorite structure, were clearly detected. By monitoring the most intense of these reflections, 112, as a function of the CeO2content, the tetragonal–cubic phase boundary was found to be at 85 (5) mol% CeO2. For a CeO2content up to 68 mol%, a tetragonal phase withc/a> 1 (known as thet′ form) was detected, whereas, between 68 and 85 mol% CeO2, the existence of a tetragonal phase withc/a= 1 and oxygen anions displaced from their ideal positions in the cubic phase (thet′′ form) was verified. Finally, solid solutions with higher CeO2contents exhibit the cubic fluorite-type phase.

High-Temperature X-Ray Powder Diffraction Study on the Phase Transition between the α-Quartz and the β-Cristobalite-Like Phase of GaPO4

2000 ◽  
Vol 321-324 ◽  
pp. 914-917 ◽  
Author(s):  
P.M. Worsch ◽  
B. Koppelhuber-Bitschnau ◽  
F.A. Mautner ◽  
P.W. Krempl ◽  
W. Wallnöfer ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Diffraction Study ◽  
Powder Diffraction ◽  
X Ray
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