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.

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 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

Crystal Structure of the High-Temperature Phase of a Compound Sr2ZnWO6

1992 ◽  
Vol 7 (4) ◽  
pp. 226-227 ◽  
Author(s):  
Fu Zhengmin ◽  
Li Wenxiu
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Lattice Parameter ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray ◽  
Cubic System ◽  
Measured Density

AbstractThe crystal structure of the high-temperature phase of Sr2ZnWO6 prepared by air quenching from 1200° C has been determined by means of X-ray powder diffraction. β-Sr2ZnWO6 belongs to the cubic system, with space group Fm3m and a lattice parameter a = 7.9266 Å at room temperature. Its measured density is Dm = 6.93g/cm3, and each unit cell contains four formula weights.

High-Temperature Structural Studies of SrPbO3 and BaPbO3

2002 ◽  
Vol 55 (8) ◽  
pp. 543 ◽  
Author(s):  
J. R. Hester ◽  
C. J. Howard ◽  
B. J. Kennedy ◽  
R. Macquart
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
High Resolution ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Studies ◽  
X Ray ◽  
First Order

High-resolution X-ray powder diffraction studies have shown BaPbO3 to transform from an orthorhombic Imma structure at room temperature, through an intermediate I4/mcm phase, to a cubic Pm3–mstructure above 500�C. The Imma to I4/mcm transition is first order and the I4/mcm–Pm3–m transition for BaPbO3 is tricritical in nature. We find no evidence for any phase transitions in SrPbO3 up to 760�C, the structure remaining in Pnma from room temperature to 760�C.

Temperature Dependent Raman Scattering and Dielectric Permittivity Measurements of Pb1−x Srx TiO3 Films

2003 ◽  
Vol 784 ◽  
Author(s):  
V. M. Naik ◽  
M. Smith ◽  
H. Dai ◽  
P. Talagala ◽  
R. Naik ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Permittivity ◽  
Raman Spectra ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Phonon Modes ◽  
X Ray ◽  
Permittivity Measurements

ABSTRACTPb1-x Srx TiO3 (x = 0 to 1.0) films of thickness ∼ 4 μ m have been prepared on sapphire and Pt substrates by metalorganic decomposition (MOD) method. X-ray diffraction results show that the films are polycrystalline with a perovskite tetragonal phase at room temperature for x < 0.5 and a cubic phase for x > 0.5. Room temperature Raman spectra show a systematic variation of lattice vibrational modes with x. The most notable changes in the Raman spectra with x are the decrease in the splitting of A1(3TO) and E(3TO) modes and the disappearance of E(3TO) mode at x ∼ 0.6. Although the x-ray diffraction peaks for films with x > 0.5 show a cubic phase at room temperature, the Raman spectra show the characteristic phonon modes of a tetragonal phase even at x = 0.7. The dielectric permittivity versus temperature measurements for films with x ≤ 0.7 show a broad dielectric anomaly corresponding to a diffuse ferroelectric to paraelectric phase transition. The phase transition temperature (Tc) values are consistently lower than the corresponding bulk ceramic alloys. Furthermore, Tc are also determined by monitoring the temperature dependence of the splitting between E(3TO) and A1(3TO) phonon modes in the Raman spectra of Pb1-x Srx TiO3 films for x ≤ 0.6. There has been good agreement between the two methods.

Crystal structure of Ca1−xSrxZr4(PO4)6 (0≤x≤1)

2004 ◽  
Vol 19 (2) ◽  
pp. 153-156 ◽  
Author(s):  
Werner Fischer ◽  
Lorenz Singheiser ◽  
Debabrata Basu ◽  
Amit Dasgupta
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
High Temperature ◽  
Structural Transformation ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Lattice Parameter ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray

The crystal structure of several compounds of Ca1−xSrxZr4(PO4)6 ceramics has been investigated by X-ray powder diffraction at room temperature. All compounds form a solid solution with a unique unit cell. While the lattice parameter a of the hexagonal unit cell decreases of about 0.9% with increasing Sr content only slightly, it considerably elongates in c direction (2.8%). No structural transformation has been observed by high-temperature X-ray diffraction up to 1000 °C.

scholarly journals Двухфазность кристаллической структуры твердых растворов (1-x)PbFe-=SUB=-2/3-=/SUB=-W-=SUB=-1/3-=/SUB=-O-=SUB=-3-=/SUB=--xPbTiO-=SUB=-3-=/SUB=- (x=0.25,0.3,0.35) при комнатной температуре

2021 ◽  
Vol 91 (1) ◽  
pp. 72
Author(s):  
Н.В. Зайцева ◽  
А.А. Набережнов ◽  
Е.П. Смирнова
Keyword(s):  
Crystal Structure ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Solid Solutions ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Lead Ions ◽  
X Ray Diffraction ◽  
X Ray

The evolution of the crystal structure of (1-x) PbFe2 / 3W1 / 3O3 - хPbTiO3 solid solutions depending on the PbTiO3concentrations (at x = 0.25, 0.3, 0.35) in the region of the morphotropic phase boundary was studied using x-ray diffraction at room temperature. It was established that all three compositions are a mixture of cubic and tetragonal phases, and an increase in the concentration of PbTiO3 above 30 mol. % leads to an increase of the tetragonal phase contribution. The parameters of the crystal structure and the content of both phases in these solid solutions are determined. It was shown that at room temperature there are static displacements of lead ions from the principle crystallographic positions.

Crystal structure of the anticancer drug carmustine determined by X-ray powder diffraction

2021 ◽  
pp. 1-3
Author(s):  
Carina Schlesinger ◽  
Edith Alig ◽  
Martin U. Schmidt
Keyword(s):  
Crystal Structure ◽  
Anticancer Drug ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Commercial Sample ◽  
One Dimensional ◽  
X Ray ◽  
Hydrogen Bond Pattern

The structure of the anticancer drug carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, C5H9Cl2N3O2) was successfully determined from laboratory X-ray powder diffraction data recorded at 278 K and at 153 K. Carmustine crystallizes in the orthorhombic space group P212121 with Z = 4. The lattice parameters are a = 19.6935(2) Å, b = 9.8338(14) Å, c = 4.63542(6) Å, V = 897.71(2) ų at 153 K, and a = 19.8522(2) Å, b = 9.8843(15) Å, c = 4.69793(6) Å, V = 921.85(2) ų at 278 K. The Rietveld fits are very good, with low R-values and smooth difference curves of calculated and experimental powder data. The molecules form a one-dimensional hydrogen bond pattern. At room temperature, the investigated commercial sample of carmustine was amorphous.

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