scholarly journals Thermoresponsive studies of porous and non-porous borophosphates.

2014 ◽  
Vol 70 (a1) ◽  
pp. C504-C504
Author(s):  
Mashikoane Mogodi ◽  
David Billing
Keyword(s):  
Thermal Expansion ◽  
Variable Temperature ◽  
Hexagonal Lattice ◽  
Linear Thermal Expansion ◽  
Lattice Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Group I ◽  
Lattice Space ◽  
Helical Channels

In this work we present the synthesis and structure-property investigation of anhydrous low porosity borophsophates [1] BPO4 and porous (NH4)0.5M1.25(H2O)2)(BP2O8)(H2O)0.5 M = Co (II), Mn (II) and NH4Fe[BP2O8(OH)] phases. Cristobalite-type BPO4 crystallizes in the tetragonal lattice, space group I-4 (No. 82) [2]. Variable-Temperature Powder X-ray diffraction (VT-PXRD) patterns for these material were analysed by the sequential and parametric Rietveld refinement [3] protocols. Both methods were used to determine the temperature dependency of the lattice parameters and linear thermal expansion coefficient. Whereas the lattice parameters were refined freely in the sequential method, the individual cell parameters were described using an empirically derived function in the parametric method. Both refinement protocols reveal significant anisotropy along the a- and c- axis as a function of temperature, with thermal expansion coefficients of 10.6 x10-6 /0C and 2.83 x10-6 /0C, respectively. Structural changes accompanying this thermoresponsive behaviour will be discussed, including the variation of the interatomic distances and P-O-B (inter-polyhedral angle, figure 1) with temperature. The open framework (NH4)0.5M1.25(H2O)2)(BP2O8)(H2O)0.5 M = Co(II) (1a), Mn(II) (1b) and NH4Fe[BP2O8(OH)] (2) phases were synthesized under mild hydrothermal methods at 1800C. The crystal structure of the isostructural (1a) and (1b) phases were refined in the hexagonal lattice, space group P65 (no. 170) and compound (2) in the monoclinic lattice, space group P21/c (no.14). Both (1a) and (1b) phases consists of NH4+ and H2O molecules located within the helical channels running along the [001] direction with compound (2) consisting exclusively of NH4+ molecules located within the helical channels running along the [100] direction. Thermoresponsive investigation conducted by TGA analysis reveal a five, four and three step mass loss process for compounds (1a), (1b) and (2) respectively, with the final step observed at 500-7000C range. Preliminary VT-PXRD results of these compounds will also be presented.

New Perovskite Based Structures in the Bi-Sr-O System

1992 ◽  
Vol 275 ◽  
Author(s):  
Bokhimi ◽  
M. Portilla
Keyword(s):  
Cell Parameter ◽  
Crystalline Phases ◽  
Space Group ◽  
Crystalline Structures ◽  
Cell Parameters ◽  
Group I

ABSTRACTWe report one amorphous and four new crystalline phases in the Bi-Sr-0 system. The structure of three of the crystalline phases was identified. The Br10Bi6O24-y phase, which is cubic with space group Fm3m and cell parameter a = 0.8471(1) nm. The SreBi10O27-y phase, which is tetragonal with the space group I/mmm, and cell parameters a = 0.6007(1), c = 0.8376(1) nm. The SreBi10O27-y phase, which is tetragonal with space group I/mmm and cell parameters a = 1.3221(1), c = 0.4249(1) nm. We show that in the crystalline structures Sr and Bi occupy equivalent sites.

Synchrotron X-ray fiber diffraction study on the thermal expansion behavior of cellulose crystals in tension wood of Japanese poplar in the low-temperature region

Holzforschung ◽  
2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Hitomi Hidaka ◽  
Ung-Jin Kim ◽  
Masahisa Wada
Keyword(s):  
Thermal Expansion ◽  
Temperature Region ◽  
Tension Wood ◽  
Linear Thermal Expansion ◽  
Thermal Expansion Behavior ◽  
X Ray ◽  
Cell Parameters ◽  
Bonding System ◽  
Fiber Diffraction ◽  
Expansion Behavior

Abstract The thermal expansion behavior of tension wood cellulose obtained from Populus maximowiczii A. Henry was investigated by synchrotron X-ray fiber diffraction at temperatures ranging from 100 to 300 K. Three equatorial and one meridional d-spacings indexed as , 110, 200, and 004 showed a gradual linear increase with increasing temperature. Unit-cell parameters calculated from the changes in these d-spacings showed anisotropic thermal expansion behavior in the three axial directions related to the crystal structure and hydrogen-bonding system of cellulose Iβ. The linear thermal expansion coefficients (TECs) of the a-, b-, and c-axes were: α a=5.2×10-5 K-1, α b=2.1×10-5 K-1, and α c=0.4×10-5 K-1, respectively. The volume TEC was β=7.8×10-5 K-1, which was approximately 70% of previously reported values in the high-temperature region from room temperature to 250°C.

scholarly journals New data on gersdorffite and associated minerals from the Peloritani Mountains (Sicily, Italy)

2021 ◽  
Vol 33 (6) ◽  
pp. 717-726
Author(s):  
Daniela Mauro ◽  
Cristian Biagioni ◽  
Federica Zaccarini
Keyword(s):  
Crystal Structure ◽  
Microprobe Analysis ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Quartz Veins ◽  
Group I

Abstract. Gersdorffite, ideally NiAsS, and associated minerals from Contrada Zillì (Peloritani Mountains, Sicily, Italy) have been characterized through electron microprobe analysis and X-ray diffraction. Primary minerals, hosted in quartz veins, are represented by gersdorffite, tetrahedrite-(Fe), and chalcopyrite with minor pyrite and galena. Rare aikinite inclusions were observed in tetrahedrite-(Fe) and chalcopyrite. Gersdorffite occurs as euhedral to subhedral crystals, up to 1 mm in size, with (Sb,Bi)-enriched cores and (Fe,As)-enriched rims. Its chemical composition is (Ni0.79−0.95Fe0.18−0.04Co0.04−0.01)(As0.90−1.03Sb0.10−0.00Bi0.02−0.00)S0.98−0.92. It crystallizes in the space group P213, with unit-cell parameters a=5.6968(7) Å, V=184.88(7) Å3, and Z=4, and its crystal structure was refined down to R1= 0.035. Associated tetrahedrite-(Fe) has chemical formula (Cu5.79Ag0.07)Σ5.86(Cu3.96Fe1.59Zn0.45)Σ6.00(Sb3.95As0.17Bi0.03)Σ4.15S13.06, with unit-cell parameters a= 10.3815(10) Å, V=1118.9(3) Å3, and space group I-43m. Its crystal structure was refined to R1=0.027. Textural and crystallographic data suggest a polyphasic crystallization of gersdorffite under low-temperature conditions.

scholarly journals Crystal structure, thermal and electrotransport properties of NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) solid solutions

2021 ◽  
Vol 8 (3) ◽  
pp. 20218301
Author(s):  
A. I. Klyndyuk ◽  
Ya. Yu. Zhuravleva ◽  
N. N. Gundilovich
Keyword(s):  
Crystal Structure ◽  
Thermal Stability ◽  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Solid Solutions ◽  
Electrical Transport ◽  
Linear Thermal Expansion ◽  
Solid State Reactions ◽  
Partial Substitution ◽  
Cell Parameters

Using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. It was found that NdBa1–xSrxFeCo0.5Cu0.5O5+δ phases crystallize in tetragonal syngony (space group P4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. Partial substitution of barium by strontium in NdBaFeCo0.5Cu0.5O5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values.

Crystallographic studies of BaR2ZnO5 (R=La, Nd, Dy, Ho, Er, and Y)

1998 ◽  
Vol 13 (3) ◽  
pp. 144-151 ◽  
Author(s):  
Winnie Wong-Ng ◽  
Brian Toby ◽  
William Greenwood
Keyword(s):  
Neutron Diffraction ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Trigonal Prism ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

The crystal structures of BaR2ZnO5, where R=La, Nd, Dy, Ho, and Y, were studied by neutron diffraction, and that of the Er analog was investigated by synchrotron X-ray diffraction. Two structure types were confirmed for this series of compounds and agreed with those reported in literature. The compounds with a smaller size of R (R=Dy, Ho, Y, and Er) are isostructural to the orthorhombic “green phase (BaY2CuO5)” compounds. The cell parameters for compounds with the R=Er to Dy range from a=7.0472(1) Å to 7.0944(1) Å, b=12.3022(1) Å to 12.3885(2) Å, and c=5.6958(1) Å to 5.7314(1) Å, respectively. R is 7-fold coordinated inside a monocapped trigonal prism. These prisms share edges to form wavelike chains parallel to the long b-axis. The Ba atoms reside in 11-fold coordinated cages. The compounds which contain a larger size R (R=La and Nd) crystallize in the tetragonal I4/mcm space group, but are not isostructural to the “brown phases” BaR2CuO5. The lattice parameters for the La and Nd analogs are a=6.9118(1) Å, c=11.6002(2) Å for BaLa2ZnO5, and a=6.7608(1) Å and c=11.5442(2) Å for BaLa2ZnO5. The structure consists of ZnO4 tetrahedral groups (instead of planar CuO4 groups as found in the brown phase) with Ba ions inserted in between. The structure can be viewed as consisting of alternate layers of Zn-Ba-O and Nd-O extending infinitely in the xy plane and perpendicular to the z-axis.

Synthesis and Crystal Structures of ATi[Nb6Cl18] Compounds (A = K, Rb, Cs, In, Tl)

2000 ◽  
Vol 55 (2) ◽  
pp. 139-144 ◽  
Author(s):  
A. Nägele ◽  
E. Anokhina ◽  
J. Sitar ◽  
H.-J. Meyer ◽  
A. Lachgar
Keyword(s):  
Structure Refinement ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Coordination Environment ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Crystal System ◽  
Rhombohedral Crystal

Abstract New quaternary niobium cluster chlorides corresponding to the general formula ATi[Nb6Cl18] (A = K, Rb, Cs, In, Tl) have been synthesized in sealed quartz tubes at 720 °C, starting from stoichiometric amounts of NbCl5, niobium metal, TiCl3, and ACl (A = K, Rb, Cs), or In or Tl metals. The structures of RbTi[Nb6Cl18] and CsTi[Nb6Cl18] were determined using single­ crystal X-ray diffraction. RbTi[Nb6Cl18] crystallizes in the rhombohedral crystal system, space group R3̄ (no. 148), Z = 3, with lattice parameters: a = 9.163(4), c = 25.014(14) Å (hexagonal setting). The structure refinement converged to R1 = 0.044 and wR2 = 0.058 for all data. In this structure, discrete [Nb6Cl18]4-cluster units are linked by Rb+ and Ti3+ cations, located in a 12-coordinated anticubeoctahedral and octahedral chloride coordination environment, respectively. In contrast, CsTi[Nb6Cl18] crystallizes in the trigonal crystal system, space group P3̄1c (no. 163), Z = 2. The lattice parameters were determined to be a = 9.1075(6), c = 17.0017(8) Å. The structure refinement gives the reliability factors R1 = 0.029 and wR2 = 0.063 for all data. The structure is built up of discrete octahedral [Nb6Cl18]4- cluster units, linked by Cs+ and Ti3+ cations which are located in a distorted hexagonal antiprismatic and octahedral chloride coordination environment, respectively. The structures of the compounds ATi[Nb6Cl18] (A = K, In, Tl) were found to be isotypic with RbTi[Nb6Cl18], and their unit cell parameters were refined using X-ray powder diffraction analysis.

Polymorphism in the negative thermal expansion material magnesium hafnium tungstate

2008 ◽  
Vol 23 (1) ◽  
pp. 210-213 ◽  
Author(s):  
Amy M. Gindhart ◽  
Cora Lind ◽  
Mark Green
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Variable Temperature ◽  
Negative Thermal Expansion ◽  
Orthorhombic Phase ◽  
High Energy ◽  
X Ray Diffraction ◽  
Space Group ◽  
Smooth Change ◽  
Energy Ball

Magnesium hafnium tungstate [MgHf(WO4)3] was synthesized by high-energy ball milling followed by calcination. The material was characterized by variable- temperature neutron and x-ray diffraction. It crystallized in space group P21/a below 400 K and transformed to an orthorhombic structure at higher temperatures. The orthorhombic polymorph adopted space group Pnma, instead of the Pnca structure commonly observed for other A2(MO4)3 materials (A = trivalent metal, M = Mo, W). In contrast, the monoclinic polymorphs appeared to be isostructural. Negative thermal expansion was observed in the orthorhombic phase with αa = −5.2 × 10−6 K−1, αb = 4.4 × 10−6 K−1, αc = −2.9 × 10−6 K−1, αV = −3.7 × 10−6 K−1, and αl = −1.2 × 10−6 K−1. The monoclinic to orthorhombic phase transition was accompanied by a smooth change in unit-cell volume, indicative of a second-order phase transition.

Synthesis and characterization of dimethyl- and dimethoxyphenylbis(N,N-dialkyldithiocarbamato)tellurium(IV) and chlorodimethyl- and chlorodimethoxyphenyl-(N,N-dialkyldithiocarbamato)tellurium(IV). Crystal structures of Me2Te[S2CNMe2]2 and (p-MeOC6H4)2Te[S2CNMe2]2

1993 ◽  
Vol 71 (1) ◽  
pp. 42-50 ◽  
Author(s):  
Jane H. E. Bailey ◽  
John E. Drake
Keyword(s):  
Nmr Spectroscopy ◽  
Crystal Structures ◽  
Variable Temperature ◽  
Reductive Elimination ◽  
Synthesis And Characterization ◽  
Space Group ◽  
Cell Parameters

The compounds Me2Te[S2CNR2]2, Me2TeCl[S2CNR2], (p-MeOC6H4)2Te[S2CNR2]2, and (p-MeOC6H4)2TeCl[S2CNR2], where R = Me, Et, have been prepared and characterised primarily by vibrational and NMR spectroscopy. Variable temperature NMR spectroscopy and qualitative time studies indicate that in solution the dimethoxyphenyltellurium derivatives undergo the reductive-elimination noted for analogous phenyl derivatives but the reductive-elimination does not occur with the dimethyl tellurium derivatives. The crystal structures of Me2Te[S2CNMe2]2, 1, and (p-MeOC6H4)2-Te[S2CNMe2]2, 5, were completed. The cell parameters for 1, which crystallizes as monoclinic in space group P21/n, are a = 13.550(2), b = 13.034(2), c = 17.854(2) Å, β = 106.61(1)°, V = 3021.6(7) Å3, Z = 8, R = 0.0368, and Rw = 0.0402 and for 5, which crystallizes as monoclinic in space group C2/c, are a = 35.36(1), b = 11.063(3), c = 12.778(3) Å, β = 96.16(3)°, V = 4963(3) Å3, Z = 8, R = 0.0627, and Rw = 0.0646.

An X-ray determination of the thermal expansion of α-phase Cu–Si alloys at high temperature

1989 ◽  
Vol 22 (4) ◽  
pp. 380-381
Author(s):  
S. K. Pradhan ◽  
M. De
Keyword(s):  
Thermal Expansion ◽  
Linear Thermal Expansion ◽  
Solute Concentration ◽  
Lattice Parameters ◽  
Thermal Expansion Coefficients ◽  
Solid Solution Range ◽  
Expansion Coefficients ◽  
Increasing Temperature ◽  
Room Temperature Increase

Lattice parameters for four Cu–Si alloys containing 2.2, 4.3, 6.4 and 8.7 at.% Si in the solid-solution range have been calculated in the temperature range 303–928 K. The lattice parameters increase slowly in a nonlinear manner with rise in temperature. The calculated linear thermal-expansion coefficients (α) at room temperature increase with increasing solute concentration (Si) but decrease almost linearly with increasing temperature, the rate of decrease being higher for alloys with higher solute concentration. All the alloys have almost the same average α value (α av ~ 16.0 × 10−6 K−1), which is the value of α at the temperature interval 615–625 K for all the alloy compositions.

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