Beiträge zum thermischen Verhalten von Sulfaten, IV* Neues zum Verhalten von PbSO4 bei höherer Temperatur / Contributions to the Thermal Behaviour of Sulfates, IV* New Facts About the Behaviour of PbSO4 at Higher Temperature

1979 ◽  
Vol 34 (3) ◽  
pp. 431-433 ◽  
Author(s):  
Manfred Spieß ◽  
Reginald Gruehn
Keyword(s):  
High Temperature ◽  
Crystal Structures ◽  
Thermal Behaviour ◽  
Room Temperature ◽  
X Ray ◽  
Temperature Form ◽  
Higher Temperature ◽  
Thermal Dilatation ◽  
High Temperature Form

Abstract Thermal Behaviour, Crystal Structures, Modifications Using the high temperature Guinier technique the transformation of the room temperature form N-PbSO4 to the cubic high-temperature form H-PbSO4 was observed. The nonquenchable H-PbSO4 modification crystallizes in the α-NaClO4-type with a(900°) = 7,23 Å, Z = 4 and dX-ray (900 °C) = 5,33 g/cm3 . The thermal dilatation of N-and H-PbSO4 was measured.

The Application of X-Ray Diffraction at Elevated Temperatures to Study the Mechanism of Formation of Sodium Tripolyphosphate

1961 ◽  
Vol 5 ◽  
pp. 276-284
Author(s):  
E. L. Moore ◽  
J. S. Metcalf
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Amorphous Phase ◽  
Elevated Temperatures ◽  
Sodium Tripolyphosphate ◽  
X Ray Diffraction ◽  
Mechanism Of Formation ◽  
X Ray ◽  
Temperature Form ◽  
High Temperature Form

AbstractHigh-temperature X-ray diffraction techniques were employed to study the condensation reactions which occur when sodium orthophosphates are heated to 380°C. Crystalline Na4P2O7 and an amorphous phase were formed first from an equimolar mixture of Na2HPO4·NaH2PO4 and Na2HPO4 at temperatures above 150°C. Further heating resulted in the formation of Na5P3O10-I (high-temperature form) at the expense of the crystalline Na4P4O7 and amorphous phase. Crystalline Na5P3O10-II (low-temperature form) appears after Na5P3O10-I.Conditions which affect the yield of crystalline Na4P2O7 and amorphous phase as intermediates and their effect on the yield of Na5P3O10 are also presented.

Dimorphic ThNi2P2 with BaCu2S2 and CaBe2Ge2 Type Structure

1994 ◽  
Vol 49 (8) ◽  
pp. 1074-1080 ◽  
Author(s):  
Jörg H. Albering ◽  
Wolfgang Jeitschko
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Crystal Structures ◽  
Type Structure ◽  
Variable Parameters ◽  
Higher Symmetry ◽  
X Ray ◽  
Coordination Numbers ◽  
Structure Factors ◽  
High Temperature Form

Two modifications of ThNi2P2 were prepared in a tin flux at 850 °C (α-ThNi2P2) and 1000 °C (β-ThNi2P2). The crystal structures of both modifications were refined from single­crystal X-ray data. α-ThNi2P2 (BaCu2S2 type structure): Pnma. a = 819.69(5), b = 394.28(3), c = 981.54(7) pm. R = 0.028 for 32 variables and 654 structure factors: β-ThNi2P2 (CaBe2Ge2 type structure): P4/nmm, a = 408.5(1), c = 908.0(3) pm, R = 0.033 for 15 variable parameters and 261 F values. Although the two structures are closely related, they can be transformed into each other only by a reconstructive phase transformation. The differences and similari­ties of the two structures are discussed. The high temperature form has higher symmetry, a smaller number of variable positional parameters, and a tendency for higher coordination numbers.

High-pressure syntheses and crystal structures of orthorhombic DyGaO3 and trigonal GaBO3

2015 ◽  
Vol 70 (4) ◽  
pp. 207-214 ◽  
Author(s):  
Daniela Vitzthum ◽  
Stefanie A. Hering ◽  
Lukas Perfler ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
High Pressure High Temperature

AbstractOrthorhombic dysprosium orthogallate DyGaO3 and trigonal gallium orthoborate GaBO3 were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 8.5 GPa/1350 °C and 8 GPa/700 °C, respectively. Both crystal structures could be determined by single-crystal X-ray diffraction data collected at room temperature. The orthorhombic dysprosium orthogallate crystallizes in the space group Pnma (Z = 4) with the parameters a = 552.6(2), b = 754.5(2), c = 527.7(2) pm, V = 0.22002(8) nm3, R1 = 0.0309, and wR2 = 0.0662 (all data) and the trigonal compound GaBO3 in the space group R3̅c (Z = 6) with the parameters a = 457.10(6), c = 1419.2(3) pm, V = 0.25681(7) nm3, R1 = 0.0147, and wR2 = 0.0356 (all data).

scholarly journals High-Pressure Syntheses, Crystal Structures, And Thermal Behaviour Of β-Re(Bo2)3 (Re = Nd, Sm, Gd)

2007 ◽  
Vol 62 (6) ◽  
pp. 765-770 ◽  
Author(s):  
Holger Emme ◽  
Gunter Heymann ◽  
Almut Haberer ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Crystal Structures ◽  
Thermal Behaviour ◽  
Diffraction Data ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Conditions

The compounds β -RE(BO2)3 [RE = Nd (neodymium meta-borate), Sm (samarium meta-borate) and Gd (gadolinium meta-borate)] were synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 3.5 GPa (Nd), 7.5 GPa (Sm, Gd) and 1050 °C. The crystal structures were determined by single crystal X-ray diffraction data collected at r. t. (Sm, Gd) and at−73°C (Nd), respectively. The structures are isotypic with the already known ambient-pressure phases β -RE(BO2)3 (RE = (Tb, Dy) and the high-pressure phases β -RE(BO2)3 (RE = Ho-Lu)

scholarly journals Comparison of the crystal structures of the low- and high-temperature forms of bis[4-(dimethylamino)pyridine]dithiocyanatocobalt(II)

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Christoph Krebs ◽  
Inke Jess ◽  
Christian Näther
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Three Dimensional ◽  
Monoclinic Space Group ◽  
Temperature Form ◽  
Dimensional Network ◽  
High Temperature Form

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-dimethylaminopyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thiocyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C—H...S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C—H...S and C—H...N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.457 g cm−3) is lower than that of the low-temperature form II (ρ = 1.462 g cm−3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive intermolecular hydrogen bonding in form II might be responsible.

X-ray and mössbauer evidence for a high temperature form of Na2SnF6

1990 ◽  
Vol 25 (8) ◽  
pp. 1035-1041 ◽  
Author(s):  
J. Grannec ◽  
L. Fournès ◽  
P. Lagassié
Keyword(s):  
High Temperature ◽  
X Ray ◽  
Temperature Form ◽  
High Temperature Form

scholarly journals Investigation of the Polymorphism of Osmium Tetrachloride

1969 ◽  
Vol 24 (2) ◽  
pp. 200-205 ◽  
Author(s):  
Paul Machmer
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependent ◽  
Orthorhombic Unit Cell ◽  
Magnetic Susceptibilities ◽  
X Ray ◽  
Space Groups ◽  
Temperature Form ◽  
High Temperature Form ◽  
First Ionization Potential

Depending on the method of preparation, osmium tetrachloride may be obtained in two different crystalline modifications, namely the high-temperature and the low-temperature forms. Both these species have been identified by elemental analysis and characterised by their respective x-ray powder photographs and magnetic susceptibilities. The x-ray powder data of the high-temperature form are tentatively rationalized in terms of an orthorhombic unit cell with the following dimensions: a = 12.08 A, b = 11.96 Å and c = 11.68 A. From the x-ray powder digram of the lowtemperature form the cubic lattice constant a = 9.95 Å is deduced. Reflection conditions for hkl and h00 are indicative of the space groups 06(P4332) and 07(P4132). Both compounds are paramagnetic and display low magnetic susceptibilities as a consequence of strong spin-orbit coupling. The high-temperature form exhibits the temperature-independent magnetic susceptibility χmole = +1080 × 10-6 c.g.s. units, whereas for the low-temperature form the value is χmole = +880 × 10-6 c.g.s. units (at 300°K). The latter susceptibility is temperature dependent. Some regularities between the uptake of chlorine by second- and third-row transition metals and the first ionization potential of the metals involved are discussed.

X-ray investigation of bredigite

1952 ◽  
Vol 29 (217) ◽  
pp. 875-884 ◽  
Author(s):  
Audrey M. B. Douglas
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Single Crystal ◽  
Hexagonal Phase ◽  
Natural Mineral ◽  
X Ray ◽  
Temperature Form ◽  
County Antrim ◽  
High Temperature Form ◽  
Different Sources

The X-ray work described below has been done on crystals of bredigite obtained from two different sources, the natural mineral from Scawt Hill, County Antrim, and the synthetic mineral from spiegeleisen slags. Both types of material have been fully deseribed by Tilley and Vincent (1948). Their analysis shows that the slag mineral is a calcium orthosilicate in which Ca is partly replaced by Mg, Mn, and Ba, the extent of the replacement being represented by the formula (Cal.59Ba0.08Mg0.31Mn0.09)SiO4. Tilley and Vincent conclude that this orthorhombic (pseudo-hexagonal) phase is identical with the high-temperature form α' of pure Ca2SiO4, the existence of which was suggested by Bredig (1943a), and confirmed by TrSmel (1949) using a high-temperature powder camera. Bredig (1943a) also suggests, on the basis of a comparison of X-ray powder patterns, that the crystal structure of α'-Ca2SiO4 is similar to that of β-K2SO4. The present single-crystal work was originally undertaken in order to investigate the structure of α'-Ca2SiO4 more fully.

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