Raman studies of the temperature dependence of the internal vibrations of the ammonium ions in the mixed crystals K[sub 1−x]A[sub x]DP and R[sub 1−x]A[sub x]DP

2001 ◽  
Vol 27 (1) ◽  
pp. 61 ◽  
Author(s):  
A. V. Van’kevich
Keyword(s):  
Temperature Dependence ◽  
Mixed Crystals ◽  
Ammonium Ions ◽  
Internal Vibrations

Optical Spectroscopy of Mixed Metamagnetic FexCo1-xCl2 Crystals

1980 ◽  
Vol 35 (10) ◽  
pp. 1013-1019 ◽  
Author(s):  
Friedrich Seitz ◽  
Terence E. Wood ◽  
Peter Day
Keyword(s):  
Charge Transfer ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Optical Spectroscopy ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Broad Band ◽  
Mixed Crystals ◽  
Magnetic Exchange

Abstract Electronic absorption spectra are reported for single crystals of composition FexCo1-xCl2 as a function of temperature from 300 K to 4 K. A broad band at 436 nm is assigned to Fe (II) → Co (II) charge transfer and the temperature dependence of its intensity is related to the magnetic exchange between the ions. The 2T1g(2H) excitation of Co (II) in the mixed crystals has an unusual temperature dependence which correlates with the Néel temperature.

Das Spektrum der verzögerten Fluoreszenz in Anthracen-und Naphthalin-Kristallen

1970 ◽  
Vol 25 (5) ◽  
pp. 657-664 ◽  
Author(s):  
K. W. Benz ◽  
W. Hacker ◽  
H. C. Wolf
Keyword(s):  
Temperature Dependence ◽  
High Purity ◽  
Trap Depth ◽  
Delayed Fluorescence ◽  
Mixed Crystals ◽  
Pure Crystal ◽  
Guest Molecules ◽  
Prompt Fluorescence ◽  
Broad Continuum

The spectra of delayed fluorescence of high purity anthracene and naphthalene crystals have been measured as a function of temperature. Below 50 °K they are very different from the spectra of prompt fluorescence. The spectra of delayed fluorescence are the superposition of three types of subspectra: different X-traps-spectra, a broad continuum, and the pure crystal spectrum. From the temperature dependence of the relative intensities of these spectra one can measure the trap depth. - It is shown that the delayed fluorescence is at least 100 times more sensitive against traps and guest molecules than the prompt fluorescence. This is demonstrated using naphthalene-anthracene mixed crystals.

Electrochemical preparation and properties of the mixed-crystalline hexavanadates MxM′4−xV6O16, M, M′ = NH4, K, Rb, Cs

1990 ◽  
Vol 68 (8) ◽  
pp. 1283-1292 ◽  
Author(s):  
E. Andrukaitis ◽  
P. W. M. Jacobs ◽  
J. W. Lorimer
Keyword(s):  
Chemical Analysis ◽  
Alkali Metal ◽  
Mixed Crystals ◽  
Continuous Series ◽  
Alkali Metal Cations ◽  
X Ray Diffraction ◽  
Ammonium Ions ◽  
Electrochemical Preparation ◽  
X Ray ◽  
End Members

Coherent deposits of oriented, crystalline MxM′4−xV6O16+δ, with M, M′ = K, Rb, Cs, or NH4, 0.0 ≤ x ≤4.0 and 0.00 ≤ δ ≤ 0.13, have been prepared electrochemically on various conducting substrates from metavanadate solutions containing ammonium or alkali metal cations, singly or in combination. Chemical analysis and X-ray diffraction show that the deposits consist of a continuous series of mixed crystals based on the isomorphic end members M4V6O16 and M′4V6O16.The deposits can be oxidized electrochemically, with removal of M and M′ atoms, and the products can be used as cathodes for insertion of lithium, with the largest capacity achieved about 1.0 mol% of total vanadium. Cycling of the electrodes improves capacity, with insertion of lithium reaching 25 mol% of total vanadium. This gain in capacity results from further removal of alkali metal or ammonium ions from the electrode during the oxidation step of the cycling process.The results extend the range of composition of homogeneous phases in the system (NH4)2O–K2O–V2O4–V2O5. Keywords: alkali metal hexavanadates, electrochemical preparation.On a préparé des dépôts cohérents qui contiennent des cristaux orientés de MxM′4−xV6O16+δ, avec M, M′ = K, Rb, Cs ou NH4, 0,0 ≤ x ≤4,0 et 0,00 ≤ δ ≤ 0,13, par la méthode de voltammétrie cyclique sur des substrats divers et dans des solutions de metavanadates qui contiennent des cations des métaux alcalins ou d'ammonium seuls ou des combinations de tels ions. L'analyse chimique et la diffraction des rayons X ont démontré que les dépôts comprennent une série continue de cristaux mixtes basée sur les membres terminaux M4V6O16 et M′4V6O16.

The thermodynamics of mixed crystals of ammonium chloride and ammonium bromide. - III. The heat capacity from 8 to 300 K of solid solutions of composition NH 4 Br 0.20 Cl 0.80 and NH 4 Br 0.74 Cl 0.26

1981 ◽  
Vol 375 (1762) ◽  
pp. 351-359
Keyword(s):  
Heat Capacity ◽  
Ammonium Chloride ◽  
Solid Solutions ◽  
Mixed Crystal ◽  
Mixed Crystals ◽  
Ammonium Bromide ◽  
Ammonium Ions ◽  
Β Phase ◽  
Δ Phase ◽  
Entropy Of Transition

The heat capacity of the mixed crystals NH 4 Br 0.20 CI 0.80 and NH 4 Br 0.74 CI 0.26 has been measured from ca . 8 to 300 K. The first of these solids has, as expected, two gradual transitions, the lower having an entropy of transition ∆ S λ of 3.79 J K –1 mol –1 , and the upper a ∆ S λ of 4.51 J K –1 mol –1 . The heat capacity between these two transitions is always considerably above the ‘normal’ or baseline value, and it appears that the orientational disordering of the ammonium ions, while completed in the γ → β transition, commences in the δ-phase. The other, bromide-rich mixed crystal shows no sign of a δ → γ transition, but has a λ -type γ → β transition which culminates at 262.5 K, with ∆ S λ = 7.31 J K –1 mol –1 . The heat capacity of both mixed crystals in the β-phase, like that of the pure components, is ‘anomalously’ high, the additional heat capacity for the solid solutions being larger than that for the pure salts. The phase diagram for the ammonium-chloride–ammonium-bromide system is shown; it combines previous information with that provided by the heat-capacity results reported in this and previous papers.

Konzentrations-und Temperaturabhängigkeit der Sensibilisierten Verzögerten Fluoreszenz in Naphthalin/Anthracen-Mischkristallen / Sensitized Delayed Fluorescence in Naphthalene/Anthracene Mixed Crystals: Concentration and Temperature Dependence

1975 ◽  
Vol 30 (3) ◽  
pp. 277-286 ◽  
Author(s):  
H. Port ◽  
M. Bader ◽  
G. Weber ◽  
H. C. Wolf
Keyword(s):  
Energy Transfer ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Energy Transport ◽  
Delayed Fluorescence ◽  
Mixed Crystals ◽  
Temperature Range ◽  
Host Molecules ◽  
Hopping Model ◽  
Triplet Excitons

The delayed fluorescence of naphthalene crystals doped with anthracene has been investigated for concentrations between 7 × 10-9 and 10-5mol/mol in the temperature range 4.2 -300 °K. The concentration dependence of both the quantum ratio of host and guest emission and of the lifetime shows the effectivity of energy transfer by triplet excitons. It can be described quantitatively within the statistical hopping model, which includes the probability for an exciton to visit the same host molecules repetitively before becoming trapped. This incoherent energy transport becomes faster as the temperature is lowered. The exciton hopping time decreases monotonically from tʜ = 2 × 10-10 sec at 300 °K to tʜ = 8 × 10-11 sec at 130 °K. Below 100 °K the delayed fluorescence is governed by competing trapping effects.

Temperature dependence of luminescence in mixed crystals

1987 ◽  
Vol 38 (1-6) ◽  
pp. 275-277 ◽  
Author(s):  
Jun'ichirō Nakahara ◽  
Shigeru Minomura ◽  
Hiroshi Kukimoto ◽  
Fujio Minami ◽  
Koh Era
Keyword(s):  
Temperature Dependence ◽  
Mixed Crystals

Estimating the temperature dependence of the dielectric constant of multiphased mixed crystals

2008 ◽  
Vol 104 (2) ◽  
pp. 026103 ◽  
Author(s):  
Vassiliki Katsika-Tsigourakou ◽  
Aglaia Vassilikou-Dova
Keyword(s):  
Dielectric Constant ◽  
Temperature Dependence ◽  
Mixed Crystals

Local, 2d and 3d Orientational Orders of the Ammonium Ions in Rb x (NH 4 ) 1- x AlF 4 Mixed Crystals

1987 ◽  
Vol 3 (1) ◽  
pp. 61-65 ◽  
Author(s):  
A Jouanneaux ◽  
A Leble ◽  
J. C Fayet ◽  
J. L Fourquet
Keyword(s):  
Mixed Crystals ◽  
Ammonium Ions ◽  
2D And 3D
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