Crystal structure, electrical, and thermal properties of Ca0.5Th0.5VO4

2009 ◽  
Vol 24 (12) ◽  
pp. 3551-3558 ◽  
Author(s):  
S.J. Patwe ◽  
S. Nagabhusan Achary ◽  
Avesh K. Tyagi
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Rietveld Refinements ◽  
Cell Parameters ◽  
Expansion Behavior ◽  
High Temperature Xrd ◽  
Zircon Type

Ca0.5Th0.5VO4 was prepared by a solid-state reaction of component oxides and characterized by powder x-ray diffraction (XRD) at ambient and higher temperatures and impedance spectroscopy. Crystal structure was refined by Rietveld refinements from powder XRD data. At room temperature, Ca0.5Th0.5VO4 has a zircon-type tetragonal (I41/amd) lattice with unit cell parameters: a = 7.2650(1) and c = 6.4460(1) Å. Despite the large charge difference, Ca2+ and Th4+ are statistically distributed over a single site. The crystal structure of Ca0.5Th0.5VO4 is built from the (Ca/Th)O8 (bisdisphenoid) and VO4 tetrahedra. The in situ high-temperature XRD studies on Ca0.5Th0.5VO4 revealed anisotropic thermal expansion behavior with coefficients of thermal expansion αc = 10.96 × 10−6/°C and αa = 5.32 × 10−6/°C. The impedance measurements carried out in the temperature range from ambient to 800 °C indicate semiconducting behavior with appreciable ionic conductivity above 400 °C. The activation energy obtained from the temperature-dependent AC conductivity data is ∼1.37 eV. In wider range of frequencies and temperatures, the relative permittivity of approximately 50 to 60 is observed for Ca0.5Th0.5VO4.

Structure and Thermal Expansion Behavior of Dy2-xGdxMo4O15 Solid Solution

2008 ◽  
Vol 368-372 ◽  
pp. 1665-1667
Author(s):  
M.M. Wu ◽  
X.L. Xiao ◽  
Y.Z. Cheng ◽  
J. Peng ◽  
D.F. Chen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Thermal Expansion ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Cell Volumes

A new series of solid solutions Dy2-xGdxMo4O15 (x = 0.0-0.9) were prepared. These compounds all crystallize in monoclinic structure with space group P21/c. The lattice parameters a, b, c and unit cell volumes V increase almost linearly with increasing gadolinium content. The intrinsic thermal expansion coefficients of Dy2-xGdxMo4O15 (x = 0.0 and 0.25) were obtained in the temperature range of 25 to 500°C with high-temperature X-ray diffraction. The correlation between thermal expansion and crystal structure was discussed.

scholarly journals Synthesis, Structure and Thermophysical Properties of Phosphates MNi0.5Zr1.5(PO4)3 (M = Mg, Ca, Sr)

2010 ◽  
Vol 12 (3,4) ◽  
pp. 241 ◽  
Author(s):  
M.V. Sukhanov ◽  
I.A. Schelokov ◽  
V.I. Pet'kov ◽  
E.R. Gobechiya ◽  
Yu.K. Kabalov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
High Temperature ◽  
Single Phase ◽  
Rietveld Method ◽  
Type Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Expansion Behavior

<p>New phosphates MNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> (M = Mg, Ca, Sr) were prepared by the precipitating method.<strong><em> </em></strong>Phosphates were characterized using X-ray powder diffraction, IR-spectroscopy and electron microprobe analyses. The crystal structure of phosphates was refined by the Rietveld method. Phosphates CaNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> and SrNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> are shown to have been crystallized in the NaZr<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>-type structure and the phosphate MgNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3 </sub>was obtained as a single-phase with Sc<sub>2</sub>(WO<sub>4</sub>)<sub>3</sub>-type structure. Heat capacity of phosphate CaNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> was measured in the range 7 – 650 K and increased monotonically over the entire temperature range studied. Thermal expansion of phosphate CaNi<sub>0.5</sub>Zr<sub>1.5</sub>(PO<sub>4</sub>)<sub>3</sub> was studied in the interval 295-1073 K by the high temperature X-ray diffraction. This phosphate is similar to the best low-expansion ceramics, such as zircon, cordierite and silica glass in thermal expansion behavior.</p>

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.

Energetic materials: variable-temperature crystal structure of β-NTO

2003 ◽  
Vol 36 (2) ◽  
pp. 280-285 ◽  
Author(s):  
Nadezhda B. Bolotina ◽  
Elizabeth Zhurova ◽  
A. Alan Pinkerton
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Energetic Materials ◽  
Variable Temperature ◽  
Thermal Motion ◽  
X Ray Diffraction ◽  
Cell Parameters ◽  
Thermal Expansion Tensor ◽  
Principal Axes ◽  
Molecular Dynamics Calculations

The crystal structure of the metastable β form of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (β-NTO, monoclinic,P21/c) has been investigated at five temperatures in the range 100–298 K using single-crystal X-ray diffraction techniques. The second-rank thermal expansion tensor has been determined to describe thermal behavior of the crystal. The most significant thermal expansion is in a plane, which is almost perpendicular to the planes of all the NTO molecules. Perpendicular to the plane of maximal thermal expansion, a modest thermal contraction takes place. Both thermal expansion and contraction of the crystal lattice indicate anharmonicity of the atomic thermal motion. The experimental thermal variation of the unit-cell parameters is in qualitative agreement with that previously obtained from molecular dynamics calculations. Rigid-body analysis of the molecular thermal motion was performed using the libration and translation second-rank tensors. Although the translation part of the thermal motion is not strongly anisotropic, the largest displacements of the NTO molecules are oriented in the plane of maximal thermal expansion of the crystal and have significant anharmonic components. The libration motion is more anisotropic, and the largest libration as well as the largest translation principal axes are directed along the C5—N5 bond in each NTO molecule.

Crystal structure and thermal properties of compound K2Zn3(P2O7)2

2008 ◽  
Vol 23 (4) ◽  
pp. 317-322 ◽  
Author(s):  
L. N. Ji ◽  
G. M. Cai ◽  
J. B. Li ◽  
J. Luo ◽  
J. K. Liang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Heating Curve ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

K2Zn3(P2O7)2 was synthesized by solid state reaction and its crystal structure was determined by ab initio method from powder X-ray diffraction (XRD) data. The title compound was determined to be orthorhombic with space group P212121, Z=4, and lattice parameters a=12.901(8) Å, b=10.102(6) Å, and c=9.958(1) Å. Values of lattice parameters from 303 to 573 K were measured by temperature-dependent XRD. Thermal expansion coefficients α0, lattice parameters, and cell volume at 0 K were determined to be α0(a)=1.62327×10−4/K, a0=12.855(4) Å, α0(b)=1.17921×10−4/K, b0=10.070(8) Å, α0(c)=2.62364×10−4/K, c0=9.880(4) Å, and α0(V)=6.599×10−2/K, V0=1278.967(0) Å3. The specific heat equation as a function of temperature was determined to be Cp=0.77115+0.00231T−1241.60027T−2−1.4133×10−6T2 (J/K g), for temperatures from 198 to 710 K. The melting point estimated from the μ-DTA heating curve is 795 °C.

Thermal expansion behavior study of Co nanowire array with in situ x-ray diffraction and x-ray absorption fine structure techniques

2008 ◽  
Vol 93 (17) ◽  
pp. 171912 ◽  
Author(s):  
Guang Mo ◽  
Quan Cai ◽  
Longsheng Jiang ◽  
Wei Wang ◽  
Kunhao Zhang ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Fine Structure ◽  
Nanowire Array ◽  
X Ray Diffraction ◽  
Thermal Expansion Behavior ◽  
X Ray ◽  
Behavior Study ◽  
Expansion Behavior ◽  
X Ray Absorption

Low-temperature investigation of natural iron-rich oxoborates vonsenite and hulsite: thermal deformations of crystal structure, strong negative thermal expansion and cascades of magnetic transitions

2021 ◽  
Vol 77 (6) ◽  
Author(s):  
Yaroslav P. Biryukov ◽  
Almaz L. Zinnatullin ◽  
Mikhail A. Cherosov ◽  
Andrey P. Shablinskii ◽  
Roman V. Yusupov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
Thermal Expansion ◽  
Diffraction Data ◽  
Magnetic Transitions ◽  
X Ray Diffraction ◽  
Critical Temperatures ◽  
X Ray ◽  
Cell Parameters ◽  
First Time

This work is devoted to an investigation of the magnetic properties and thermal behaviour of the natural oxoborates vonsenite and hulsite in the temperature range 5–500 K. The local environment, the oxidation states of the Fe and Sn atoms, and the charge distribution were determined using Mössbauer spectroscopy and are in accordance with a refinement of the crystal structure of hulsite from single-crystal X-ray diffraction data (SCXRD) in anisotropic approximation for the first time. The magnetic properties were studied by vibrating sample magnetometry (VSM) (5 ≤ T ≤ 400 K) and are reported for the first time for iron-rich hulsite. Both oxoborates show a very complex magnetic behaviour. Cascades of magnetic transitions are revealed and the critical temperatures were determined. The sequences of magnetic transitions in both vonsenite and hulsite with increasing temperature were found to be as follows: magnetically ordered state → partial magnetic ordering → paramagnetic state. According to X-ray diffraction data (93 ≤ T ≤ 500 K), these processes are accompanied by anomalies in the unit-cell parameters and thermal expansion of the oxoborates at critical temperatures. A strong negative volume thermal expansion is observed for both oxoborates at temperatures below ∼120 K.

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