Crystal structures of (Ba1−xLax)[Mg(1+x)/3Nb(2−x)/3]O3 with 0.9 ≤ x ≤ 1.0

2003 ◽  
Vol 18 (4) ◽  
pp. 1003-1010 ◽  
Author(s):  
Hyun Min Park ◽  
Hwack Joo Lee ◽  
Yang Koo Cho ◽  
Sahn Nahm
Keyword(s):  
Single Phase ◽  
Weight Fraction ◽  
Crystal Structure Analysis ◽  
Structure Model ◽  
X Ray Diffraction ◽  
Minor Phase ◽  
Two Phase ◽  
Rietveld Refinements ◽  
The Matrix ◽  
A Minor

Based on a structure model of mixture of phases, the crystal structure analysis of (Ba1−xLax)[Mg(1+x)/3Nb(2−x)/3]O3 (BLMN) (x = 0.9 and 1.0) by Rietveld refinements was carried out. The pure La(Mg2/3Nb1/3)O3 (LMN) and BLMN (x=0.9) actually consist of a two-phase mixture rather a single phase. One is Fm-3m, which is cubic and 1:1 ordered and the other is P21/n, which is monoclinic and has both 1:1 ordering and the antiphase and inphase tilting of oxygen octahedra with a−a−c+. The weight fraction of the Fm-3m phase is 17.5% at x=0.9 and further decreases to 7.5% in pure LMN. Meanwhile, that of the P21/n phase is 82.5% at x =0.9 and further increases to 92.5% in pure LMN. The I4/m phase, which is present as a minor phase from x=0.3 to 0.7, disappeared when x≥0.9. The abrupt change of the x-ray diffraction pattern at x=0.9 is caused by a change of major phase from Fm-3m to P21/n phase in the matrix.

Hydride structures in Ti-aluminides subjected to high temperature and hydrogen pressure charging conditions

1991 ◽  
Vol 6 (6) ◽  
pp. 1230-1237 ◽  
Author(s):  
D. Legzdina ◽  
I.M. Robertson ◽  
H.K. Birnbaum
Keyword(s):  
Single Phase ◽  
Vacuum Annealing ◽  
Lattice Parameter ◽  
Matrix Composition ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
The Matrix ◽  
Diffraction Patterns ◽  
Fcc Structure

The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and x-ray diffraction techniques. The alloys were exposed at 650 °C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 °C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride. The hydrogen content in the two-phase (γ-α2) alloy was approximately three times that of the single phase alloy, which was presumably a consequence of the presence of the α2-Ti3Al phase in the two-phase alloy. The hydrides in the two-phase material were shown by x-ray diffraction to have an fcc structure and were removed on annealing in vacuum at 800 °C for 24 h.

Synthesis of sinteractive single-phase microstructure yttrium disilicate precursor powder using hydrothermal processing

1998 ◽  
Vol 13 (11) ◽  
pp. 3135-3143 ◽  
Author(s):  
P. A. Trusty ◽  
K. C. Chan ◽  
C. B. Ponton
Keyword(s):  
Single Phase ◽  
Precursor Powder ◽  
Hydrothermal Processing ◽  
X Ray Diffraction ◽  
Interpenetrating Network ◽  
Two Phase ◽  
Yttrium Chloride ◽  
Order Of Magnitude ◽  
Acidic Conditions ◽  
Yttrium Disilicate

This paper is the first report of the synthesis of a sinteractive single-phase microstructure yttrium disilicate precursor powder using hydrothermal processing. The effect of the pH of the precursor chemicals on the ease of formation of a single-phase material was investigated using x-ray diffraction, TEM, and SEM. Under very acidic conditions (pH 1), the formation of yttrium chloride, in addition to the yttrium disilicate precursors, produced a powder that absorbed moisture, did not sinter well, and produced a two-phase interpenetrating microstructure after sintering. At pH 6, yttrium chloride no longer formed, but the interpenetrating network persisted after sintering. Only under basic conditions (pH 10) did single-phase yttrium disilicate form after sintering. This work is noteworthy because the calcination time of 1 h required for the formation of this ceramic at 1050 °C is over an order of magnitude lower than the calcination times of over 100 h required when calcined in the temperature range 900 °C to 1150 °C, as reported previously by other workers.

scholarly journals The Polythermal Section of Ti-22Al-xNb (30-78at.%Ti) in Ti–Al–Nb System

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 871
Author(s):  
Yun Zhao ◽  
Li-Bin Liu ◽  
Li-Gang Zhang ◽  
Jia-Jun Yang ◽  
Patrick J. Masset
Keyword(s):  
Single Phase ◽  
Invariant Reaction ◽  
Polythermal Section ◽  
Electron Probe Micro Analysis ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Three Phase ◽  
Micro Analysis ◽  
O Phase

The polythermal section of Ti-22Al-xNb (30–78 at.% Ti) in the Ti-Al-Nb system was studied using X-ray diffraction analysis (XRD), differential thermal analysis (DSC), and electron probe micro-analysis (EPMA). No new ternary compounds were found in this work. The polythermal section has five three-phase regions, nine two-phase regions, and three single-phase regions. The O phase transition is confirmed to occur below 1000 °C. A four-phase invariant reaction β + σ → O + δ was found at 931 °C.

Oxidation of Zirconium-Yttrium Alloys

1964 ◽  
Vol 8 ◽  
pp. 143-150 ◽  
Author(s):  
D. I. Phalen ◽  
D. A. Vaughan ◽  
N. A. Richard
Keyword(s):  
Single Phase ◽  
Phase Distribution ◽  
Zirconium Alloys ◽  
Metallic Elements ◽  
Air Oxidation ◽  
X Ray Diffraction ◽  
Metal Interface ◽  
Two Phase ◽  
Anion Diffusion ◽  
Metal Composition

AbstractThe phase and elemental distributions on zirconium alloys containing 5, 10, 25, 35, and 50 at.%. yttrium, oxidized in dry air at 1200 and 1600°C, have been studied by X-ray diffraction, fluorescence, and electron-microprobe techniques. Zirconium-yttrium alloys, which are entirely solid at 1200°C, and zirconium 5 and 25 at.% yttrium alloys, which aire two-phase solid plus liquid at 1600°C, form a multiphase scale of ZrO2, Y2O3, and ZrN. The phase distribution varies with yttrium content, while the average metal composition remains constant throughout the oxide scale and base metal. In contrast, zirconium 35 and 50 at.% yttrium alloys, which are entirely liquid at 1600°C, form a single-phase Y2O3 layer.The mechanism of air oxidation of solid zirconium-yttrium alloys, up to 50 at. % yttrium, is one of anion diffusion to the oxide-metal interface with little or no diffusion of the metallic elements. The oxidation of liquid alloys differs in that, as a result of yttrium diffusion to the oxide-liquid interface, Y2O3 is the only oxide formed. Ternary Zr-Y-O isotherms are presented to illustrate the phase distribution and mode of formation.

Crystal-structure analysis of four mineral samples of anhydrite, CaSO4, using synchrotron high-resolution powder X-ray diffraction data

2011 ◽  
Vol 26 (4) ◽  
pp. 326-330 ◽  
Author(s):  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Unit Cell Volume ◽  
Crystal Structure Analysis ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Rietveld Refinements ◽  
X Ray ◽  
Cell Parameters

The crystal structures of four samples of anhydrite, CaSO4, were obtained by Rietveld refinements using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and space group Amma. As an example, for one sample of anhydrite from Hants County, Nova Scotia, the unit-cell parameters are a = 7.00032(2), b = 6.99234(1), c = 6.24097(1) Å, and V = 305.487(1) Å3 with a > b. The eight-coordinated Ca atom has an average <Ca-O> distance of 2.4667(4) Å. The tetrahedral SO4 group has two independent S-O distances of 1.484(1) to O1 and 1.478(1) Å to O2 and an average <S-O> distance of 1.4810(5) Å. The three independent O-S-O angles [108.99(8) × 1, 110.38(3) × 4, 106.34(9)° × 1; average <O-S-O> [6] = 109.47(2)°] and S-O distances indicate that the geometry of the SO4 group is quite distorted in anhydrite. The four anhydrite samples have structural trends where the a, b, and c unit-cell parameters increase linearly with increasing unit-cell volume, V, and their average <Ca-O> and <S-O> distances are nearly constant. The grand mean <Ca-O> = 2.4660(2) Å, and grand mean <S-O> = 1.4848(3) Å, the latter is longer than 1.480(1) Å in celestite, SrSO4, as expected.

Crystal structure of low-cristobalite-type Al0.5Ga0.5PO4: A combined Rietveld refinement of neutron and X-ray diffraction data

2005 ◽  
Vol 20 (3) ◽  
pp. 207-211 ◽  
Author(s):  
S. N. Achary ◽  
A. K. Tyagi ◽  
S. K. Kulshreshtha ◽  
O. D. Jayakumar ◽  
P. S. R. Krishna ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Cell Parameters ◽  
Bond Lengths

The low-cristobalite-type modification of Al0.5Ga0.5PO4 is prepared by annealing the amorphous precipitate of stoichiometric phosphate at 1300 °C. The phase purity of the sample is ascertained by powder X-ray diffraction. The crystal structure is refined by Rietveld refinements of the neutron and X-ray diffraction data of the polycrystalline powder. This compound crystallizes in an orthorhombic lattice with unit cell parameters, a=7.0295(8), b=7.0132(8), and c=6.9187(4) Å, V=341.08(6) Å3, Z=4 (Space group C 2221, No. 20). The crystal structure analysis reveals the random distribution of the Al3+ and Ga3+ having tetrahedral coordination with typical M–O (M=Al3+:Ga3+) bond lengths as 1.74 Å. Similarly, the P5+ have tetrahedral coordination with typical P–O bond lengths 1.52–1.54 Å. The Mo4 and PO4 tetraheda are linked by common corners forming a three-dimensional framework lattice. The details of the crystal structure are presented in this paper.

Effect of Cao from Different Sources on the Nanostructured Cordierite

2011 ◽  
Vol 364 ◽  
pp. 368-371 ◽  
Author(s):  
Ibrahim Norfadhilah ◽  
Mohamad Hasmaliza ◽  
Zainal Arifin Ahmad ◽  
J. Banjuraizah
Keyword(s):  
Xrd Analysis ◽  
Oxide Material ◽  
X Ray Diffraction ◽  
Minor Phase ◽  
Major Phase ◽  
X Ray ◽  
Pure Oxide ◽  
Crystallite Sizes ◽  
A Minor ◽  
Different Sources

Cordierite was synthesized via glass-route using mineral and pure oxide material. Kaolin, talc, dolomite, magnesia, alumina, silica, and calcium oxide were mixed and melted. CaO from mineral and pure oxide was added in order to investigate the properties of each material in cordierite system. Sample was characterized using X-ray diffraction (XRD) analysis and dilatometer testing. The result showed that when 5wt% CaO from mineral (C5 Min) was added and sintered at 900°C, α-cordierite exist as major phase and anorthite as a minor phase. While for a sample consists of 5wt% CaO from pure oxide (C5 Ox), α-cordierite was present as major phases, µ-cordierite and anorthite as minor phases. Crystallite sizes of each material were in nanorange and crystallite size of C5 Ox was less than C5 Min.

Reactive Synthesis of TiAl/Ti5Si3 In Situ Composites

2011 ◽  
Vol 217-218 ◽  
pp. 684-687
Author(s):  
Jian Feng Zhu ◽  
Wen Wen Yang ◽  
Shao Dan Li
Keyword(s):  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Microstructural Characteristics ◽  
Powder Mixtures ◽  
X Ray ◽  
Reactive Synthesis ◽  
In Situ Composite ◽  
The Matrix ◽  
A Minor

Full dense and highly pure TiAl/Ti5Si3 in situ composite was successfully synthesized by reactive synthesis from the powder mixtures of Ti, Al and Si. The reaction process was investigated in detail by the X-ray diffraction analysis (XRD) and differential scanning calorimetry (DSC). The microstructural characteristics of the TiAl/Ti5Si3 in situ composite were also studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the as fabricated composite possesses three phases, namely, TiAl, Ti3Al and Ti5Si3. The matrix phases are mainly equiaxed TiAl with a minor lamellar Ti3Al phase. Ti5Si3 particles with size less than 1 μm are distributed uniformly in matrix grains as a reinforcing phase.

Assessment of the X-ray diffraction–absorption method for quantitative analysis of largely amorphous pharmaceutical composites

2003 ◽  
Vol 36 (1) ◽  
pp. 74-79 ◽  
Author(s):  
P. Bergese ◽  
I. Colombo ◽  
D. Gervasoni ◽  
Laura E. Depero
Keyword(s):  
Weight Fraction ◽  
Toxic Waste ◽  
X Ray Diffraction ◽  
Amorphous Halo ◽  
Scanning Calorimetry ◽  
X Ray ◽  
The Matrix ◽  
Diffraction Patterns ◽  
Challenging Question

Determination of the residual weight fraction of a crystalline drug in a largely amorphous pharmaceutical composite is still a challenging question. None of the quantitative X-ray diffraction (QXRD) methods found in the literature is suitable for these inclusion systems. The composite's diffraction patterns present a structured amorphous halo (arising from the amorphous matrix and drug molecular clusters) in which the crystalline drug peaks rise up. Moreover, the matrix traps a non-negligible quantity of water (which cannot be directly detected by X-ray diffraction) and the crystal structure of the drug may be unknown. In this work, a development of the QXRD analysis based on the diffraction–absorption technique is presented. The method is standardless, avoids the interpretation of the amorphous halo and the knowledge of the crystal structures of the phases, and takes into account the absorbed water. Results are in excellent agreement with those obtained by differential scanning calorimetry (DSC). The general features of the technique open its application to other classes of largely amorphous composite materials, like glass systems generated in the stabilization/solidification of toxic waste.

scholarly journals Carbon nanofibers addition on transport and superconducting properties of bulk YBa2Cu3O7−δ material prepared via co-precipitation

2020 ◽  
Vol 31 (19) ◽  
pp. 16983-16990
Author(s):  
Nurul Auni Khalid ◽  
Mohd Mustafa Awang Kechik ◽  
Nur Atikah Baharuddin ◽  
Chen Soo Kien ◽  
Hussein Baqiah ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Carbon Nanofibers ◽  
Precipitation Method ◽  
Superconducting Properties ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
Minor Phase ◽  
X Ray ◽  
Co Precipitation ◽  
A Minor

Abstract The effects of carbon nanofibers addition on transport and superconducting properties of YBa2Cu3O7−δ (Y-123) superconductor were studied. Y-123 was prepared using co-precipitation method for good quality bulk of high temperature superconducting material. Carbon nanofibers with 0.2–0.8 wt% were added into Y-123 superconductors. The samples were characterized using electrical resistance measurement for critical temperature (Tc) and critical current density (Jc), powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis. Most of the samples indicated a dominant Y-123 phase of an orthorhombic structure with a minor phase of BaCO3 and Y-124. Onset critical temperature was found to decrease from 90.5 to 80 K with increasing of carbon nanofibers concentration. The Jc for pure sample is 11 A/cm2 at 30 K while the Jc of sample with 0.4 wt% carbon nanofibers is 830 A/cm2 at 30 K. Introduction of carbon nanofibers enhanced Jc significantly. However, further addition of carbon nanofibers in Y-123 superconductor caused degradation in Jc.

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