Rietveld refinement and diffuse phases transition of Ba1-XBixTi0.8Fe0.2O3 ceramics at x=0.00, 0.05, 0.10 and 0.15 prepared by solid state method.

2020 ◽  
Author(s):  
Najwa Gouitaa ◽  
LAMCHARFI Taj-dine ◽  
Mfadal BOUAYAD ◽  
ABDI Farid ◽  
Mustapha Haddad
Keyword(s):  
Phase Transitions ◽  
Rietveld Refinement ◽  
Tetragonal Phase ◽  
Structural Parameters ◽  
Hexagonal Phase ◽  
Complex Impedance ◽  
Rhombohedral Phase ◽  
Cubic Phase ◽  
Solid State Method ◽  
X Ray

Abstract The effect of substitution of Baryum by Bismut in site A and titanium by iron in site A on structural, physical and electrical properties of Ba1-xBixTi0.80Fe0.20O3 ceramics at (x=0.00, 0.05, 0.10 and 0.15) was investigated by X-ray diffraction, Scaning Electron Microscopy (SEM) as well as dielectric characterizations. The crystal phase was studied by using rietveld refinement. The result of rietveld refinement of X-ray powders diffraction of Ba1-xBixTi0.80Fe0.20O3 shows that these compounds crystallize in tetragonal (P4mm) and hexagonal (P63mmc) for x=0.00 and 0.05 while at x=0.10 and 0.15 the hexagonal phase disappears and the tetragonal phase is stabilized. The structural parameters and the R-factors of these ceramics were succefully determined by the rietveld refinement. The Raman spectra confirms the disappearance of hexagonal phase in benefit of tetragonal phase as the Bi substitution increases. The dielectric measurements as function of temperature are studied and showed tree diffuse phase transitions transition from the ferroelectric rhombohedral phase to the ferroelectric orthorhombic TR-O phase and the second one is from the ferroelectric orthorhombic phase to the ferroelectric TO-T tetragonal phase. While the third one at high temperatures is the phase transition from the ferroelectric tetragonal phase to the paraelectric cubic phase Tm. These phases transition were displaced to the lower temperature with increasing of Bi substitution. And the value of dielectric permittivity increases gradually with increasing of Bi2+ contents. All these phase transitions showed a diffused phenomenon which can be well described by fitting the modified Ushino relation, 1/ε’r = 1/ε’r,max [ 1+ ((T-Tm)/2δ)γ]. The complex impedance Cole–Cole plots showed negative temperature coefficient of resistivity (NTCR) behavior of the Ba1-xBixTi0.80Fe0.20O3 for x=0.05 to 0.15 materials and decrease in grain and grain boundaries resistivity. The relaxation behavior in the test materials is found to be of Debye type.

scholarly journals Peculiarities of the Crystal Structure Evolution of BiFeO3–BaTiO3 Ceramics across Structural Phase Transitions

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 801 ◽  
Author(s):  
Dmitry V. Karpinsky ◽  
Maxim V. Silibin ◽  
Sergei V. Trukhanov ◽  
Alex V. Trukhanov ◽  
Alexander L. Zhaludkevich ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Phase Boundary ◽  
Structural Parameters ◽  
Structural Phase ◽  
Rhombohedral Phase ◽  
Phase Evolution ◽  
Structure Evolution ◽  
Cubic Phase ◽  
Scanning Calorimetry

Evolution of the crystal structure of ceramics BiFeO3–BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral–cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use.

Rietveld Refinement of the BaTiO3 from X-Ray Powder Diffraction

2009 ◽  
Vol 79-82 ◽  
pp. 593-596
Author(s):  
Feng Sun ◽  
Yan Sheng Yin
Keyword(s):  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Ferroelectric Ceramic ◽  
Powder Diffraction Data ◽  
Ceramic Powders ◽  
Space Group ◽  
X Ray

The ferroelectric ceramic BaTiO3 was synthesized at 1000 °C for 5 h. The structure of the system under study was refined on the basis of X-ray powder diffraction data using the Rietveld method. The system crystallizes in the space group P4mm（99）. The refinement of instrumental and structural parameters led to reliable values for the Rp, Rwp and Rexp.We use the TOPAS software of Bruker AXS to refine this ceramic powders and show its conformation

Phase transitions in ReO3studied by high-pressure X-ray diffraction

2000 ◽  
Vol 33 (2) ◽  
pp. 279-284 ◽  
Author(s):  
J.-E. Jørgensen ◽  
J. Staun Olsen ◽  
L. Gerward
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Powder Diffraction ◽  
Ambient Pressure ◽  
Rhombohedral Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Ions ◽  
Pressure Phase ◽  
Related Phase

ReO3has been studied at pressures up to 52 GPa by X-ray powder diffraction. The previously observed cubicIm3¯ high-pressure phase was shown to transform to a monoclinic MnF3-related phase at about 3 GPa. All patterns recorded above 12 GPa could be indexed on rhombohedral cells. The compressibility was observed to decrease abruptly at 38 GPa. It is therefore proposed that the oxygen ions are hexagonally close packed above this pressure, giving rise to two rhombohedral phases labelled I and II. The zero-pressure bulk moduliBoof the observed phases were determined and the rhombohedral phase II was found to have an extremely large value of 617 (10) GPa. It was found that ReO3transforms back to thePm3¯mphase found at ambient pressure.

scholarly journals Phase Transition in Di-oleoylphosphatidylglycerol/Monoolein Membranes due to Interactions of Positively Charged Peptides at their Lipid Membrane-Interface

1970 ◽  
Vol 45 (3) ◽  
pp. 219-224
Author(s):  
Shah Md Masum ◽  
Masahito Yamazaki
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Small Angle ◽  
Lipid Membrane ◽  
Cubic Phase ◽  
Membrane Interface ◽  
X Ray ◽  
X Ray Scattering ◽  
Charged Peptides ◽  
Positively Charged

To elucidate the factors that induce phase transitions in biomembranes due to interactions of proteins/peptides at the lipid membrane-interface, the effects of positively charged peptides on the cubic phase (Q229) of Dioleoylphosphatidylglycerol (DOPG)/Monoolein (MO) membranes were investigated. Small angle X-ray Scattering (SAXS) results revealed that 12 mol% DOPG/88 mol % MO membranes in excess water at 25°C is body centered cubic phase of crystallographic space group Im3m (Q229). In presence of peptide LLKKK, the lattices constant of Q229 phase was gradually decreased with an increase of peptide concentration and a phase transition from cubic (Q229) to cubic (Q224) phase occurred at R=0.080; (R= molar ratio of peptide to lipid). On the other hand the designed peptide WLFLLKKK and antimicrobial peptide Magainin-2 induced lamellar phase (Lα) in the same mixture membranes. These results indicate that the interactions of the these peptides with this mixture membrane are different: LLKKK induces electrostatic attractive interactions and that of WLFLLKKKK and Magainin-2 bound with the lipid membranes induce electrostatic repulsive interaction at the membrane-interface, might be the major factor inducing different phase transitions in 12 mol% DOPG/88mol% MO mixture membranes. Key words: Antimicrobial peptide Magain-2; Dioleoylphosphatidylglycerol; Monoolein; Cubic phases; Small angle X-ray Scattering DOI: 10.3329/bjsir.v45i3.6530Bangladesh J. Sci. Ind. Res. 45(3), 219-224, 2010

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.

X-ray powder diffraction data of A-formula lanthanum and titanium substituted lead zirconate

2003 ◽  
Vol 18 (3) ◽  
pp. 252-262 ◽  
Author(s):  
Else Breval ◽  
Nichole Wonderling ◽  
Joseph P. Dougherty
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Tetragonal Phase ◽  
Hexagonal Phase ◽  
Lead Zirconate ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phase Pure

PLZT of the compositions 0≤L≤12, and 0≤T≤10 was studied in order to describe the structure of the phases as a function of composition. This range contains a mixed region with PLZT+La2Zr2O7, an orthorhombic, a rhombohedral (hexagonal) phase, a tetragonal phase, and a mixture of different PLZT phases. Each phase pure composition is described by X-ray diffraction.

Phase Transitions and Thermal Expansion of 10mol%Sc2O3-1mol% CeO2-ZrO2 Ceramics

2007 ◽  
Author(s):  
Sergey Yarmolenko ◽  
Devendra Ray ◽  
Devdas Pai ◽  
Jag Sankar
Keyword(s):  
Thermal Expansion ◽  
Phase Transitions ◽  
Grain Structure ◽  
Slow Phase ◽  
Cubic Phase ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Operational Conditions ◽  
Β Phase

Phase transitions and CTE of 10mol%Sc2O3-1mol%CeO2-ZrO2 ceramics sintered from two commercial powders produced by Praxair Surface Technologies, USA and DKKK, Japan are studied. Morphology of powders and grain structure of ceramics were studied by SEM and AFM. Ceramics produced from Praxair powder exist in cubic phase while DKKK-based ceramics exhibit slow phase transformation from cubic to rhombohedral (β) phase at temperatures 350–400°C. c-β Phase transition temperature is 440°C obtained by high temperature x-ray diffractometry (HTXRD) and differential scanning calorimetry. Coefficients of thermal expansion of cubic and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25–800°C. These results can be further used for the optimal design of SOFC layered structures as well as for determination of their reliability and durability under operational conditions.

Solid Solutions Study of BaTiO3 Doped on B Site by Electronic Compensation

2014 ◽  
Vol 976 ◽  
pp. 30-35
Author(s):  
Francisco Raúl Barrientos-Hernández ◽  
Alberto Arenas-Flores ◽  
Iván Alonso Lira Hernández ◽  
Carlos Gómez-Yáñez ◽  
Miguel Pérez Labra
Keyword(s):  
Room Temperature ◽  
Hexagonal Phase ◽  
Ferroelectric Properties ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Solid State Method ◽  
X Ray ◽  
Air Atmosphere ◽  
Conventional Solid State Method ◽  
Electronic Compensation

Several compositions of BaTiO:Nb5+ were made by conventional solid-state method in air atmosphere, according to the general formula BaTi1-xNbxO3; (x= 0.005, 0.04, 0.08, 0.20, and 0.25). The crystal structure, microstructure, dielectric and ferroelectric properties of samples were investigated by XRD, Raman Spectroscopy, Electrical Measurements and SEM. X-ray diffraction results clearly indicated that when x ≥ 0.25 was prepared; the hexagonal phase Ba8Ti3Nb4O24 appeared. Electrical measurements at 1 kHz were carried out and several pellets were made, the relative permittivity was calculated. The dielectric constant of the pristine BaTiO3 is about 7000, and the Curie temperature is ≈120°C at room temperature, decreasing to 90°C with Nb5+ addition (x = 0.005).

Low-temperature crystal structure of RS-thiocamphor

2004 ◽  
Vol 219 (9) ◽  
Author(s):  
E. Louise R. Robins ◽  
Michela Brunelli ◽  
Asiloé J. Mora ◽  
Andrew N. Fitch
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Low Temperature ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Two Phase ◽  
X Ray ◽  
Low Temperature Crystal Structure

AbstractDSC and high-resolution powder X-ray diffraction measurements in the range 295 K–100 K show that RS-thiocamphor undergoes two phase transitions. The first, at around 260 K on cooling, is from the room-temperature body-centred-cubic phase to a short-lived intermediate. At 258 K the low-temperature form starts to appear. The crystal structure of the latter is orthorhombic, space group

Phase Stability and Sintering Behavior of 10mol%Sc2O3–1mol%CeO2–ZrO2 Ceramics

2009 ◽  
Vol 6 (2) ◽  
Author(s):  
Sergey Yarmolenko ◽  
Jag Sankar ◽  
Nicholas Bernier ◽  
Michael Klimov ◽  
Jay Kapat ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Room Temperature ◽  
Rhombohedral Phase ◽  
Impurity Level ◽  
Cubic Phase ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Chemical Route ◽  
Heating And Cooling ◽  
Secondary Ion

The phase composition and sintering behavior of two commercially available 10mol%Sc2O3–1mol%CeO2–ZrO2 ceramics produced by Daiichi Kigenso Kagaku Kogyo (DKKK) and Praxair have been studied. DKKK powders have been manufactured using a wet coprecipitation chemical route, and Praxair powders have been produced by spray pyrolysis. The morphology of the powders, as studied by scanning electron microscopy, has been very different. DKKK powders were presented as soft (∼100μm) spherical agglomerates containing 60–100nm crystalline particles, whereas the Praxair powders were presented as sintered platelet agglomerates, up to 30μm long and 3–4μm thick, which consisted of smaller 100–200nm crystalline particles. X-ray diffraction analysis has shown that both DKKK and Praxair powders contained a mixture of cubic (c) and rhombohedral (r) phases: 79% cubic +21% rhombohedral for DKKK powders and 88% cubic +12% rhombohedral for Praxair powders. Higher quantities of the Si impurity level have been detected in Praxair powder as compared to DKKK powder by secondary ion mass spectroscopy. The morphological features, along with differences in composition and the impurity level of both powders, resulted in significantly different sintering behaviors. The DKKK powders showed a more active sintering behavior than of Praxair powders, reaching 93–95% of theoretical density when sintered at 1300°C for 2h. Comparatively, the Praxair powders required high sintering temperatures at 1500–1600°C. However, even at such high sintering temperatures, a significant amount of porosity was observed. Both DKKK and Praxair ceramics sintered at 1300°C or above exist in a cubic phase at room temperature. However, if sintered at 1100°C and 1200°C, the DKKK ceramics exist in a rhombohedral phase at room temperature. The DKKK ceramics sintered at 1300°C or above exhibit cubic to rhombohedral and back to cubic phase transitions upon heating at a 300–500°C temperature range, while Praxair ceramics exist in a pure cubic phase upon heating from room temperature to 900°C. However, if heated rather fast, the cubic to rhombohedral phase transformation could be avoided. Thus it is not expected that the observed phase transitions play a significant role in developing transformation stresses in ScCeZrO2 electrolyte upon heating and cooling down from the operation temperatures.

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