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'Phase Transition' in keywords Facet   Publication Year 1993  [X]
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1993[X]
1Author    R. Jakubas, G. Bator, M. Foulon, J. Lefebvre, J. MatuszewskiRequires cookie*
 Title    Structural Phase Transitions in (/i-C 3 H 7 NH3) 2 SbBr 5  
 Abstract    Dielectric, DSC, thermal expansion and preliminary X-ray diffraction studies on (/i-C 3 H 7 NH3) 2 SbBr 5 are reported. It was found that this crystal undergoes a complex sequence of phase transitions. On cooling: phase I phase II at 188.7 K (continuous), II -» • III at 165 K (1st order, z!S = 26.8 J/mol K), III IV at 137 K (1st order, 1.6 J/mol K). On heating: IV III at 154 K, III II' at 168 K, II' -> II at 177 K (1st order, 2.8 J/mol K), II I at 189 K. All 1st order phase transitions are likely due to the motion of the n-C 3 H 7 NH3 cations. The dielectric dispersion studies between 100 Hz-1 MHz within the phases I and II indicate a fast reorientational motion of dipoles with T < 10" 7 s. 
  Reference    Z. Naturforsch. 48a, 529—534 (1993); received October 7 1992 
  Published    1993 
  Keywords    Alkylammonium halogenoantimonates, Phase transition, Dielectric, DSC, Thermal expansion 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0529.pdf 
 Identifier    ZNA-1993-48a-0529 
 Volume    48 
2Author    J. Reuter, T. Brückert, A. WürflingerRequires cookie*
 Title    Differential Thermal Analysis under Pressure on Cyanocyclohexane, 1,2,3,4-Tetrahydro-5,6-dimethyl-1,4-methanonaphthalene, and 2-Methyl-2-propanol  
 Abstract    Differential thermal analysis has been performed on cyanocyclohexane (CCH), 1,2,3,4-tetrahydro-5,6-dimethyl-1,4-methanonaphthalene (TDMN), and 2-methyl-2-propanol (t-butanol) up to 300 MPa. The latter compound was also investigated dielectrically. CCH displays an ODIC phase that transforms only reluctantly to the low-temperature stable phase II. Annealing under pressure can appreciably accelerate this transformation. For all three compounds the phase diagrams were established. For CCH and TDMN also the pressure dependence of the glass transition has been determined. 
  Reference    Z. Naturforsch. 48a, 705—708 (1993); received March 10 1993 
  Published    1993 
  Keywords    High pressure, DTA, Phase transitions, Glass transition, Dielectric constant 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0705.pdf 
 Identifier    ZNA-1993-48a-0705 
 Volume    48 
3Author    W. Medycki, R. Jakubas, N. Piślewski, J. LefebvreRequires cookie*
 Title    NMR and Dilatometric Studies on [N(CH 3 ) 4 1 3 M 2 X 9 (M = Sb, Bi; X = C1, Br)  
 Abstract    Thermal expansion studies on [N(CH 3) 4 ] 3 Sb-,Cl 9 and [N(CH 3) 4 ] 3 Sb 2 Br 9 are reported. The relax-ation times 'H T, were measured for [N(CH 3) 4 ] 3 Bi 2 Cl 9 , [N(CH 3) 4 ] 3 Sb 2 Br 9 , and [N(CH 3) 4 ] 3 Bi 2 Br 9 in the temperature range 100-290 K. To interpret the 7\ data on [N(CH 3) 4 ] 3 Bi 2 Cl 9 the method of Tj calculation reported by Takeda et al. has been applied successfully. Two different, inequivalent types of [N(CH 3) 4 ] 3 cations for all tetramethylammonium crystals are found. 
  Reference    Z. Naturforsch. 48a, 748—752 (1993); received January 31 1993 
  Published    1993 
  Keywords    Tetramethylammonium crystals, Phase transitions, Thermal expansion, 'H spin-lattice relaxation time 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0748.pdf 
 Identifier    ZNA-1993-48a-0748 
 Volume    48 
4Author    Stefan Jurga, Kazimierz Jurga, EduardC. Reynhardt, Piotr KatowskiRequires cookie*
 Title    A Proton NMR Study of n-Decylammonium Chain Dynamics in the Perovskite-type Layered Compound (C 10 H 21 NH3) 2 CdCl4  
 Abstract    A detailed proton second moment and spin-lattice relaxation time investigation of the bilayered compound (C 10 H 21 NH 3) 2 CdCl 4 is reported. In the low temperature phase the methyl group exe-cutes a classical threefold reorientation, while the NH 3 group is involved in a similar reorientation in an asymmetric potential well. Evidence for defect chain motions in this phase has been found, and infomation regarding the potential wells associated with these motions has been extracted from the data. In the high temperature phase, slow chain defect motions and fast fourfold reorientations of chains about their long axes, parallel to the normal to the bilayer, have been observed. 
  Reference    Z. Naturforsch. 48a, 563—569 (1993); received October 9 1992 
  Published    1993 
  Keywords    Bilayered compounds, Phase transition, Spin-lattice relaxation, Molecular motions, Defect motions 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0563.pdf 
 Identifier    ZNA-1993-48a-0563 
 Volume    48