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 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.

Structural phase transitions and photoluminescence properties of Eu3+ doped Ca(2−x)BaxLaNbO6 phosphors

2015 ◽  
Vol 44 (42) ◽  
pp. 18536-18543 ◽  
Author(s):  
Jicheng Zhu ◽  
Zhiguo Xia ◽  
Yuanyuan Zhang ◽  
Maxim S. Molokeev ◽  
Quanlin Liu
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Structural Phase ◽  
Luminescence Properties ◽  
Structure Evolution ◽  
Structural Phase Transitions ◽  
Photoluminescence Properties

Crystal structure evolution and luminescence properties of Eu3+ doped Ca(2−x)BaxLaNbO6 phosphors have been discussed depending on the Ca/Ba substitutions.

Influence of thermal treatment of Ti-45Nb alloy in ultrafine-grained states on its structural parameters and heat capacity

2021 ◽  
pp. 84-91
Author(s):  
E.V. Legostaeva ◽  
◽  
M.A. Khimich ◽  
Yu.P. Sharkeev ◽  
A.Yu. Eroshenko ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Structural Parameters ◽  
Structural Phase ◽  
Coherent Scattering ◽  
Normal Stresses ◽  
Two Phase ◽  
Ω Phase ◽  
Ultrafine Grained

The effect of heat treatment of the Ti-45Nb alloy in the UFG state on its structural parameters (lattice parameters, volumetric phase ratio, sizes of coherent scattering regions, residual normal stresses) and their relationship with heat capacity have been studied. It has been established that the different character of the temperature dependence of the heat capacity for the Ti-45Nb alloy in the UFG and CC states is associated with the structural-phase features of the alloy in the UFG state: the two-phase structure of a-grains and b-grains, dispersion-hardened by the ω-phase, and phase transitions in the temperature range 400-600 °С.

scholarly journals Ba5(IO6)2: crystal structure evolution from room temperature to 80 K

2021 ◽  
Vol 77 (6) ◽  
pp. 634-637
Author(s):  
David Wenhua Bi ◽  
Priya Ranjan Baral ◽  
Arnaud Magrez
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Structural Transition ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
Lattice Contraction ◽  
Interatomic Distances ◽  
Crystallographic Axes

The crystal structure of Ba5(IO6)2, pentabarium bis(orthoperiodate), has been re-investigated at room temperature based on single-crystal X-ray diffraction data. In comparison with a previous crystal structure determination by the Rietveld method, an improved precision of the structural parameters was achieved. Additionally, low-temperature measurements allowed the crystal structure evolution to be studied down to 80 K. No evidence of structural transition was found even at the lowest temperature. Upon cooling, the lattice contraction is more pronounced along the b axis. This contraction is found to be inhomogeneous along different crystallographic axes. The interatomic distances between different Ba atoms reduce drastically with lowering temperature, resulting in a closer packing around the IO6 octahedra, which remain largely unaffected.

scholarly journals Temperature-dependent phase evolution of copper-oxide thin-films on Au(111)

2018 ◽  
Vol 20 (8) ◽  
pp. 5636-5643 ◽  
Author(s):  
Christoph Möller ◽  
Hanna Fedderwitz ◽  
Claudine Noguera ◽  
Jacek Goniakowski ◽  
Niklas Nilius
Keyword(s):  
Thin Films ◽  
Phase Transitions ◽  
Dft Calculations ◽  
Copper Oxide ◽  
Structural Phase ◽  
Oxide Films ◽  
Phase Evolution ◽  
Structural Phase Transitions ◽  
Oxide Thin Films ◽  
Temperature Dependent

STM and DFT calculations are employed to explore structural phase transitions in thin copper-oxide films grown on Au(111).

Crystallographic Features of Ferroelectric States around the Tetragonal /Rhombohedral Phase Boundary in Pb1-xLax(Zr1-yTiy)O3

2010 ◽  
Vol 638-642 ◽  
pp. 1737-1742
Author(s):  
Masazumi Arao ◽  
Yasuhide Inoue ◽  
Ryoutarou Ando ◽  
Yasumasa Koyama
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dielectric Properties ◽  
Phase Boundary ◽  
Rhombohedral Phase ◽  
Relaxor Behavior ◽  
Rotational Displacement ◽  
Transmission Electron ◽  
Ti Content

To understand dielectric properties around the ferroelectric tetragonal (FT)/rhombohedral (FR) phase boundary in Pb1-xLax(Zr1-yTiy)O3, the crystallographic features of ferroelectric states around the boundary have been investigated by transmission electron microscopy. It was found that, when the Ti content approached to the phase boundary in the FT-phase area, a dielectric property became the relaxor behavior. The corresponding change in the crystallographic features is that the usual FT state is converted into the nanometer-sized coexisting state of the ferroelectric monoclinic (FM) and FR phases. Because the crystal structure of FR-phase regions in the coexisting state involves the R25-type rotational displacement of oxygen octahedra, the FR phase can be identified as the low-temperature ferroelectric rhombohedral phase that is present in Pb(Zr1-yTiy)O3. It is thus understood that the relaxor behavior found in Pb1-xLax(Zr1-yTiy)O3 should be associated with the presence of the nanometer-sized coexisting state that consists of two ferroelectric phases.

scholarly journals Investigation of structural phase evolution and dielectric response of Co-doped BaTiO3

2018 ◽  
Vol 08 (04) ◽  
pp. 1850024 ◽  
Author(s):  
Amantulla Mansuri ◽  
Ilyas Noor Bhatti ◽  
Imtiaz Noor Bhatti ◽  
Ashutosh Mishra
Keyword(s):  
Phase Transition ◽  
Structural Study ◽  
Structural Phase ◽  
Structural Evolution ◽  
Phase Evolution ◽  
Dielectric Measurement ◽  
Cubic Phase ◽  
Tangent Loss ◽  
Ionic Radii ◽  
Co Doping

In the present study, we have synthesized polycrystalline samples of BaTi[Formula: see text]CoxO3 (BTCO) ([Formula: see text], 0.01, 0.03, 0.05, 0.07 and 0.10) with standard solid state reaction technique. The obtained samples are characterized by X-ray diffraction (XRD) and Raman spectroscopy for structural study. The detailed structural analysis has been performed by Rietveld refinement using Fullprof program. We observed an increase in lattice parameters, which results due to substitution of Co[Formula: see text] with large ionic radii (0.9[Formula: see text]Å) for smaller ionic radii (0.6[Formula: see text]Å) Ti[Formula: see text]. Moreover, peak at 45.5∘ shifts to 45∘ on Co doping, which is due to structure phase transition from tetragonal to cubic. Raman study infers that the intensity of characteristic peaks decreases and line width increases with Co doping. The bands linked with the tetragonal structure (305[Formula: see text]cm[Formula: see text]) decreased due to the tetragonal-to-cubic phase transition with Co doping. Our structural study reveals the expansion of BTCO unit cell and tetragonal-to-cubic phase transformation takes place. The results from different characterization techniques are conclusive and show structural evolution with Co doping. The samples are further characterized by dielectric spectroscopy, dielectric measurement reveals the increase of dielectric constant and transition [Formula: see text]C is observed for Barium titanate (BaTiO3), whereas transition disappears with Co doping. Both temperature and frequency-dependent tangent loss is also studied.

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.

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