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'Phase Transition' in keywords Facet section ZfN Section A [X]

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1	Author	S. Lewicki, B. Szafrańska, Z. Pająk	Requires cookie*
	Title	Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide
	Abstract	The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered.
	Reference	Z. Naturforsch. 47a, 1115—1118 (1992); received July 14 1992
	Published	1992
	Keywords	NMR, Molecular motions, Phase transitions
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	Identifier	ZNA-1992-47a-1115
	Volume	47

2	Author	Barbara Szafrańska, Zdzisław Pająk	Requires cookie*
	Title	M
	Abstract	o le c u la r M o tio n in S o lid T e tr a e th y l-a n d T e tra p ro p y la m m o n iu m T e tr a f lu o r o b o r a te s Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetraethyl-and tetrapropylammonium tetrafluoroborates have been measured over a wide range of temperatures. Solid-solid phase transitions were found for both compounds and confirmed by DSC. Methyl group C3 reorientation followed by more complex cation motions was evidenced in the low temperature phases. Overall cation reorientation characterises the high temperature phases of both compounds. Isotropic anion reorientation was found in both salts in both phases.
	Reference	Z. Naturforsch. 50a, 584—588 (1995); received August 15 1994
	Published	1995
	Keywords	NMR, Molecular motions, Phase transitions
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	TEI-XML for	default:Reihe_A/50/ZNA-1995-50a-0584.pdf
	Identifier	ZNA-1995-50a-0584
	Volume	50

3	Author	M. Grottel3, A. Kozakb, Z. Pająk	Requires cookie*
	Title	l H a n
	Abstract	d 19F N M R S tu d y o f C a tio n a n d A n io n M o tio n s in G u a n id in iu m F lu o r o a n tim o n a te s Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.
	Reference	Z. Naturforsch. 50a, 742—748 (1995); received March 2 1995
	Published	1995
	Keywords	NMR, Molecular Motions, Phase transitions
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	TEI-XML for	default:Reihe_A/50/ZNA-1995-50a-0742.pdf
	Identifier	ZNA-1995-50a-0742
	Volume	50

4	Author	M. Grottel, M. Szafrański, Z. Pająk	Requires cookie*
	Title	NMR Study of Cation Motion in Guanidinium Iodoplumbates
	Abstract	Proton NMR second moments and spin-lattice relaxation times of polycrystalline C(NH 2) 3 PbI 3 and [C(NH 2) 3 ]2PbI 4 were studied in a wide temperature range. The order-disorder character of the existing solid-solid phase transitions was confirmed and for tetraiodoplumbate a new phase transition at 170 K was discovered. For both compounds a dynamical inequivalence and unusual high mobility of the guanidinium cations were revealed. For the reorientations discovered (NH 2 group flipping, C 3 in-plane reorientation and a tumbling) the activation parameters were determined.
	Reference	Z. Naturforsch. 52a, 783—788 (1997); received October 6 1997
	Published	1997
	Keywords	NMR, Molecular Motions, Phase Transitions
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	TEI-XML for	default:Reihe_A/52/ZNA-1997-52a-0783.pdf
	Identifier	ZNA-1997-52a-0783
	Volume	52

5	Author	R. Tchukvinskyi, R. Cach, Z. Czapla	Requires cookie*
	Title	Dielectric Study of the Ferroelectric Phase Transition in DMAGaS Crystal
	Abstract	Electric permittivity measurments as functions of temperature at constant dc electric field and as func-tions of the dc electric field at constant temperatures in the paraelectric phase have been performed for DMAGaS crystal. The changes of the permittivity maximum with the electric field intensity evidence the first-order character of the ferroelectric phase transition at T cX . The field dependence of the permit-tivity e(E) in the paraelectric phase is discussed, using the classical electric equation of state. A meth-od for the determination of the corresponding coefficients is proposed. The obtained B and C coeffi-cients, together with double hysteresis loop observed above T cl prove the first-order character of the ferroelectric phase transition in DMAGaS crystal.
	Reference	Z. Naturforsch. 53a, 105—111 (1998); received October 15 1998
	Published	1998
	Keywords	Ferroelectricity, Phase Transition, Dielectric Properties
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	TEI-XML for	default:Reihe_A/53/ZNA-1998-53a-0105.pdf
	Identifier	ZNA-1998-53a-0105
	Volume	53

6	Author	Akinobu Sasane, Hisanori Shinohara, Yoshihiro Mori, Yoshio Kume, Tetsuo Asaji, Daiyu Nakamura	Requires cookie*
	Title	A Temperature Dependence Study of 35 C1 Nuclear Quadrupole Resonance Frequencies in Some Hexachloroplatinate(IV) Hexahydrates
	Abstract	The temperature dependence of 35 C1 NQR frequencies was investigated in various hexachloro-platinate(IV) hexahydrates containing the following divalent ions as counter cations: Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Ba(II). All of the compounds except the Cu(II) and Ba(II) salts yield a single 35 C1 NQR line at all temperatures studied. For the Mn(II), Cu(II), and Ba(II) salts, the NQR frequencies are considerably shifted by deuteration. For the deuterated Mn(II) salt, two 35 C1 NQR lines were observed whose relative peak-height intensities vary in dependence on the history of the thermal treatment of the sample. The very broad higher frequency line could be observed for a sample which had been at 77 K or below. It could not be observed for a sample which was cooled slowly to room temperature after it had been heated up to ca. 420 K. A structural phase transition was located at 135. 6 and 129. 4 K for the Cu(II) salt and its deuterated analog, respectively. The frequency shift by deuteration is discussed in relation to the strength of O-H ... CI type hydrogen bonds.
	Reference	Z. Naturforsch. 42a, 611—616 (1987); received February 171987
	Published	1987
	Keywords	Magnetic resonance (NQR), hydrogen bonding, phase transition
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	TEI-XML for	default:Reihe_A/42/ZNA-1987-42a-0611.pdf
	Identifier	ZNA-1987-42a-0611
	Volume	42

7	Author	J. Wąsicki, Z. Pająk, A. Kozak	Requires cookie*
	Title	Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate
	Abstract	Temperature dependences of and 19 F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equiva-lent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10~ 10 s.
	Reference	Z. Naturforsch. 45a, 33—36 (1990); received August 5 1989
	Published	1990
	Keywords	NMR, cross-relaxation, molecular motions, phase transitions
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-0033.pdf
	Identifier	ZNA-1990-45a-0033
	Volume	45

8	Author	Masao Hashimoto, Akiko Shono, Yoshiyuki Mido, Haruo Niki, Hiroshi Hentona, Koichi Mano	Requires cookie*
	Title	Narrowing of the 3 5 CI NQR Lines of Trichloroacetamide Caused by Its Ferroelectric Phase Transition
	Abstract	Dielectric measurements on single crystals and DSC of the title compound (monoclinic, space group P2 X) revealed a ferroelectric transition at ca. 355 K (AH xs 0.5 kJ mol"Powder x-ray diffraction indicated that the high temperature phase is also monoclinic and the change in volume at the transition is very small. A displacement of hydrogen atoms is considered as responsible for the appearance of ferroelectricity. The 35 C1 NQR signals at ca. 77 K were considerably broad, but a drastic narrowing took place after the compound had once experienced the phase transition. A tentative assignment of the NQR spectrum was made from a calculation of the NQR frequencies based on the CNDO/2 method. Another phase transition was evidenced by a small drift of the DSC curve and a slight anomaly of the dielectric behavior around 358 K. The present *H NMR experi-ments gave no indication of the onset of torsional motion of the NH 2 group reported to occur at ca. 210 K.
	Reference	Z. Naturforsch. 45a, 327—333 (1990); received August 26 1989 in revised form November 1 1989
	Published	1990
	Keywords	NQR, Phase transition, Ferroelectricity, Hydrogen bond, Disordered structure
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-0327.pdf
	Identifier	ZNA-1990-45a-0327
	Volume	45

9	Author	J. Pirnat, J. Lužnik, Z. Trontelj, P. K. Kadaba	Requires cookie*
	Title	Iodine NQR and Phase Transitions in [N(CH 3 ) 4 ] 2 ZnI 4 * a
	Abstract	Using a superregenerative NQR spectrometer, the temperature dependence of 127 I NQR spectra in [N(CH 3) 4 ] 2 ZnI 4 was measured between 167 and 335 K. The measurements confirm two known structural phase transitions at 219 and 257.5 K. The correspondence between the distinct regions of iodine NQR spectra and the crystal structure is discussed. The relation of [N(CH 3) 4 ] 2 ZnI 4 to the incommensurate family with the general formula X 2 YZ 4 and the high temperature (paraphase) crystal space group D^ (Pmcn) is studied.
	Reference	Z. Naturforsch. 45a, 349—352 (1990); received August 23 1989 in revised form 25 November 1989
	Published	1990
	Keywords	NQR, phase transitions, ferroelectric, crystal structure, displacement modulation
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-0349.pdf
	Identifier	ZNA-1990-45a-0349
	Volume	45

10	Author	Juan Murgich, Ismardo Bonalde, JoseA. Abanero	Requires cookie*
	Title	N Nuclear Quadrupole Resonance Study of the Phase Transitions of Ba[Fe(CN) 5 N0] -3H 2 0
	Abstract	The 14 N nuclear quadrupole resonance (NQR) of the cyanides in Ba[Fe(CN) s NO] • 3H 2 0 (BNP) was observed between 77 and 293 K. Phase transitions exist at 118,131 (both weakly first order) and 233 K (second order). Most of the cyanides were perturbed by the structural changes except for one of the trans cyanides that was only affected by the transition at 131 K. The mechanism of the phase transitions is interpreted in terms of soft modes resulting from the ion rearrangement produced by the slowing down of the water molecules upon cooling. A comparison of the NQR spectrum of BNP with that of Na ? [Fe(CN) 5 NO] • 3H 2 0 showed that the substitution of Na + by Ba 2 produced only minor changes in the charge distribution of the nitroprusside ion.
	Reference	Z. Naturforsch. 45a, 353—356 (1990); received August 25 1989
	Published	1990
	Keywords	Magnetic Resonance (NQR), Nitroprussides, Phase Transitions
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-0353.pdf
	Identifier	ZNA-1990-45a-0353
	Volume	45

11	Author	J. Von Cieminski	Requires cookie*
	Title	Modeling of High-Signal Electrostriction. I
	Abstract	A thermodynamical calculation of high-signal electrostriction, especially of ferroelectric materials, is proposed. It permits to model the high-signal electrostriction of the paraelectric and the funda-mental switching behaviour of the ferroelectric phase. Extraordinary high-signal deformation curves can be explained, the influence of the thermodynamical coefficients can be estimated and the order of phase transitions can be determined experimentally from the high-signal deformation curves.
	Reference	Z. Naturforsch. 45a, 1090—1094 (1990); received May 8 1990
	Published	1990
	Keywords	Electromechanical properties, Electrostriction, Ferroelectrics, Thermodynamic, Phase transition
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-1090.pdf
	Identifier	ZNA-1990-45a-1090
	Volume	45

12	Author	J. Von Cieminski	Requires cookie*
	Title	Modeling of High-Signal Electrostriction. II
	Abstract	The predictions obtained with a thermodynamical method are compared with experimental results. Several materials which pass a ferroelectric phase transition of first or second order are investigated. The predictions correspond well with the experimentaly determined qualitative and quantitative features as to the field and temperature dependence. Finally, extraordinary strain-field curves are predicted and proved.
	Reference	Z. Naturforsch. 45a, 1095—1101 (1990); received May 8 1990
	Published	1990
	Keywords	Electromechanical properties, Electrostriction, Ferroelectrics, Thermodynamic, Phase transition
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	Identifier	ZNA-1990-45a-1095
	Volume	45

13	Author	Z. Szafrańska, A. Pająk, Kozak	Requires cookie*
	Title	B
	Abstract	Proton and fluorine NMR second moments and spin-lattice relaxation times for polycrystalline tetrabutylammonium tetrafluoroborate have been measured over a wide range of temperatures at several Larmor frequencies. An analysis of cross-relaxation effects results in a determination of activation parameters for anion and cation reorientations. Three solid phases characterized by different ion dynamics are evidenced. M o le c u la r M o tio n in S o lid T e tra b u ty la m m o n iu m T e tr a f lu o r o b o r a te
	Reference	Z. Naturforsch. 46a, 545—550 (1991); received March 14 1991
	Published	1991
	Keywords	NMR, Cross-relaxation, Molecular motions, Phase transitions
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	TEI-XML for	default:Reihe_A/46/ZNA-1991-46a-0545.pdf
	Identifier	ZNA-1991-46a-0545
	Volume	46

14	Author	MarcoL H Gruwel1, RoderickE. Wasylishen	Requires cookie*
	Title	D
	Abstract	e u te riu m N M R S tu d y o f th e S o lid -S o lid P h a s e T ra n s itio n in P h e n e th y la m m o n iu m B ro m id e 30, 1991 Using 2H NMR, the dynamics of the cation in phenethylammonium bromide were studied in the two solid phases. Line shape and spin-lattice relaxation rate studies of the ammonium headgroups and the adajacent methylene groups indicate the onset of alkyl-chain motion prior to the first order phase transition. In the low-temperature phase the line shape and the spin-lattice relaxation rates of the -ND3 groups are consistent with C3 jumps and an activation energy of 54±4 kJ mol"1. However, in the high-temperature phase the spin-lattice relaxation studies indicate the presence of small-angle diffusion of the -ND3 groups around the C3 symmetry axis. In this phase the -CD2-groups show line shapes typical of large-amplitude two-site jumps occurring at a rate > 107 s~ l. In the low-temperature phase, at temperatures below 295 K, the -CD2-2H NMR line shapes indicate that the C-D bonds are essentially static.
	Reference	Z. Naturforsch. 46a, 691 (1991); received March
	Published	1991
	Keywords	2H NMR, Phase transition, Relaxation, Molecular jumps
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	Identifier	ZNA-1991-46a-0691
	Volume	46

15	Author	S. Torre, P. Ferloni	Requires cookie*
	Title	Molecular Motion in Solid Tetramethylammonium Tetrafluoroborate
	Abstract	Measurements of n B and NMR relaxation times, differential scanning calorimetry and thermomechanical analysis, carried out on polycrystalline (CH 3) 4 NBF 4 from room temperature to about 100 K, have permitted to discuss the crystal dynamics of this salt and to analyze the nature of the phase transition occurring at «150K. Moreover, by means of an evaluation of the n B quadrupole coupling constant, information about the position of the F atoms has been obtained. An explanation of the NMR data in terms of an order-disorder phase transition involving the F~ ions is given.
	Reference	Z. Naturforsch. 47a, 721—727 (1992); received March 24 1992
	Published	1992
	Keywords	(CH 3 ) 4 NBF 4, Molecular motion, Phase transition
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	TEI-XML for	default:Reihe_A/47/ZNA-1992-47a-0721.pdf
	Identifier	ZNA-1992-47a-0721
	Volume	47

16	Author	R. Jakubas, G. Bator, M. Foulon, J. Lefebvre, J. Matuszewski	Requires 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

17	Author	Tsutomu Okuda, Yoshihiro Kinoshita, Hiromitsu Terao, Koji Yamada	Requires cookie*
	Title	Structure and Bonding of Bromoantimonate (III) Complexes with Unusual Valency by Means of NQR and Powder X-Ray Diffraction
	Abstract	NQR and powder X-ray diffraction were observed for several bromoantimonate (III) complexes which contain C"H2n+ jNF^ (n = 1 -3) or (C"H2lt + 1)2N H 2 (n = 1 -4) as a cation. The bond character, anion structure, crystal structure, and phase transition are discussed on the basis of the three-center-four-electron bond. A good correlation was found between the halogen NQR frequency and the Sb-X bond length.
	Reference	Z. Naturforsch. 49a, 185—192 (1994); received July 23 1993
	Published	1994
	Keywords	81Br NQR, Temperature dependence, Phase transition, Crystal structure
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	TEI-XML for	default:Reihe_A/49/ZNA-1994-49a-0185.pdf
	Identifier	ZNA-1994-49a-0185
	Volume	49

18	Author	Barbara Szafrańska, Zdzisław Pająk	Requires cookie*
	Title	Molecular Motion in Solid Tetraethyl-and Tetrabutylammonium Perchlorates
	Abstract	The proton N M R second moment and spin-lattice relaxation time for polycrystalline tetraethyl-and tetrabutylammonium perchlorates have been measured over a wide range of temperatures. Solid-solid phase transitions related to the onset of cation tumbling were found for both compounds and confirmed by DSC. In the low temperature phases methyl-group reorientation was evidenced. For tetrabutylammonium cation a dynamic nonequivalence of one methyl group is found. The geared motion of the alkyl chains related with the onset of successive C H 2-group reorientations is suggested.
	Reference	Z. Naturforsch. 49a, 465—468 (1994); received December 7 1993
	Published	1994
	Keywords	N M R, Molecular motions, Phase transitions
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	TEI-XML for	default:Reihe_A/49/ZNA-1994-49a-0465.pdf
	Identifier	ZNA-1994-49a-0465
	Volume	49

19	Author	J. Zaleski, R. Jakubas	Requires cookie*
	Title	The Dielectric and Dilatometric Single Crystal Studies of Phase Transitions in a New Member of Family of Halogenoantimonates(III) [C(NH2)3l2SbCl5* [C(NH2)3]C1
	Abstract	The results of dielectric, dilatometric and DSC studies on a new member of the family of alkylammonium halogenoantimonates ([(C(NH2)3]2SbCl5 • [(C(NH2)3]C1) are presented. This com pound undergoes three phase transitions at 146 K, 162 K, and 366 K. The two low temperature transitions are suggested to be of the displacive type and the high temperature one of the order-dis-order type. The character of temperature changes of the electric permittivity at the lowest temper ature transition suggest a polar phase below the transition temperature.
	Reference	Z. Naturforsch. 49a, 709—713 (1994); received March 23 1994
	Published	1994
	Keywords	Phase transitions, Dielectric, Dilatometric, Halogenoantimonate, Guanidinium
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	TEI-XML for	default:Reihe_A/49/ZNA-1994-49a-0709.pdf
	Identifier	ZNA-1994-49a-0709
	Volume	49

20	Author	Jacek Zaleski	Requires cookie*
	Title	Crystal Structure and Phase Transitions of [C(NH2)3]3Sb2C l9 * 0.9 H 20 A dam Pietraszko
	Abstract	The room temperature structure of [C(NH2)3]3Sb2C l9 ■ 0.9 H 20 (GNCA) was solved. It crystal lizes in the monoclinic C2/c space group with a = 15.275, b = 8.794, c = 17.904 (in Ä), ß = 96.40°, V = 2390 Ä 3, Z = 4. Refinement of the atomic parameters by a least squares methods gave R = 0.042, wR = 0.039 for 1958 reflections with F>4ct(F). The structure consists of polyanionic (Sb2Cl\|_)n layers built of deformed corner connected SbX^-octahedra. Two crystallographically inequivalent guanidinium cations are present, one situated between polyanionic layers, the other one together with a disordered water molecule inside cavities formed by polyanions. Temperature X-ray scattering experiments together with DSC studies were carried out above room temperature. Temperature dependence of the lattice parameters between 300 K and 380 K was determined and a phase transition of mixed order at 364 K was revealed.
	Reference	Z. Naturforsch. 49a, 895—901 (1994); received June 7 1994
	Published	1994
	Keywords	Guanidinium, Chloroantimonate, Crystal structure, Phase transition, DSC
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	Identifier	ZNA-1994-49a-0895
	Volume	49

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