High pressure Brillouin scattering and energy dispersive X-ray diffraction study of (NH4)2ZnCl4

Burris, Jennifer; Tereshchenko, Lidiia; Kaboš, Pavel; Hochheimer, H. D.; Luspin, Y.; Evenson, Carl R.; Dorhout, Peter K.

doi:10.1016/s0022-3697(99)00342-x

Cited by 12 publications

(4 citation statements)

References 24 publications

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“…Studies of high-pressure Brillouin scattering and energy dispersive X-ray diffraction of AZC between room temperature and 423 K revealed that pressure reduced the order parameter fluctuations close to the phase transition from the high-temperature orthorhombic phase to the incommensurate phase [9]. Lang et al [10] found the form and temperature dependence of ESR spectra of (NH 4 ) 2 ZnCl 4 doped with Mn 2+ in good agreement with the predictions of the phase soliton theory.…”

Section: Introductionmentioning

confidence: 73%

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals

Gaffar

El‐Fadl

Anooz

2003

Physica Status Solidi (b)

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Optical transmittance measurements were carried out near the absorption edge of (NH 4 ) 2 ZnCl 4 : x Sr 2+ single crystals, where x = 0.00, 0.020, 0.039, 0.087 or 0.144 wt%. The dependence of the absorption coefficient (α) on photon energy in the range 3.4 -6.4 eV and on temperature in the range 276 -350 K was examined. With increasing temperature the absorption edge was shifted to the lower energy side; this shift was attributed to the temperature dependence of electron-lattice interactions. Due to the presence of Sr 2+ in (NH 4 ) 2 ZnCl 4 : x Sr 2+ a change in the absorption band centred at 5.30 eV was observed. In the case of higher strontium doping, the optical absorption coefficient showed a 'pre-transition' stage just before the onset of the band-to-band transition. Exponential dependence of α on hν according to the Urbach rule was observed and the Urbach parameters were determined. The steepness parameter was strongly affected by doping; its behaviour at 319 K evidently showed the antiferroelectric to commensurate phase transition. The temperature dependence of E g was also estimated using data for the steepness parameter, and hence E g at different temperatures and Sr 2+ concentrations was evaluated.

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Section: Introductionmentioning

confidence: 73%

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals

Gaffar

El‐Fadl

Anooz

2003

Physica Status Solidi (b)

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“…In the critical region of the N to IC phase transition symmetry breaking effect in the birefringence behavior of AZC was not observed by Kim et al [4]. However Burris et al [5], performing ambient and high pressure Brillouin scattering and energy dispersive x-ray diffraction of AZC were able to detect all phase transitions in the temperature range between room temperature and 696 K. Lang et al [ 6], found the form and temperature dependence of the ESR spectra of AZC doped with Mn 2+ (as an element necessary for ESR observation) in good agreement with the predictions of the phase-soliton theory. The soliton-density did not change significantly during the whole IC phase but it dropped abruptly to zero at the IC to the C phase transition, a behavior that is quite different from those of other incommensurate systems.…”

Section: Introductionmentioning

confidence: 95%

Doping‐induced‐effects on conduction mechanisms in incommensurate ammonium zinc chloride crystals

Gaffar

El‐Fadl

Anooz

2007

Cryst. Res. Technol.

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The dc conductivity (σ) along the polar b-axis of ammonium zinc chloride (AZC) crystals in its four hightemperature phases has been measured as a function of temperature. Doping with Mn 2+ in different concentrations changed strongly both values of σ at all temperatures and the dependence of ln σ dc on 1/T in the phase transition regions. The activation energy of conduction was calculated from the linear portions of this dependence in each phase. The results were discussed in the light of the decomposition of (NH 4 ) 2 in the high-temperature normal phase, the discommensuaration (DC) formation/annihilation in the incommensurate phase and domain wall motion and stripples nucleation in the commensurate-and antiferroelectric-phases. Pinning of DC's in the crystal lattice and/or by the structural defects and the possibility of dislocation formation was also discussed. The bulk-and the electrode-limited conduction mechanisms were also considered. The current density-voltage gradient relationship according to the usual Richardson-Schottky (R-S) equation shows disagreement between extracted parameters and experimentally measured ones. A modified equation was used to solve this difficulty which, in addition, facilitated the calculation of the electronic mobility (µ), the barrier height (ϕ) at the electrode-dielectric interface and the R-S constant (β RS ). The effect of Mn 2+ -content on values of µ, ϕ and β RS in different phases of AZC was also considered.

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“…Studies on high pressure Brillouin scattering and energy dispersive X-ray diffraction of A 2 ZC 4 between the room temperature and 423 K revealed that pressure reduces the order parameter fluctuations close to the phase transition from the high temperature orthorhombic normal (N) phase to the IC-phase [6]. Lang et al [7] found the form and temperature dependence of the ESR spectra of A 2 ZC 4 doped with Mn 2+ in good agreement with the predictions of the phase-soliton theory.…”

Section: Introductionmentioning

confidence: 99%

Effects induced by chemical non-stoichiometry and γ-irradiation on the habit and unit cell parameters of ammonium tetrachlorozincate

Gaffar¹,

El‐Fadl²,

Anooz³

2006

Cryst. Res. Technol.

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The effect of chemical non-stoichiometry and γ-irradiation on the unit cell parameters of ammonium tetrachlorozincate (NH 4 ) 2 ZnCl 4 (A 2 ZC 4 ) has been studied. The unit cell parameters of crystal grown from solution with NH 4 Cl/ZnCl 2 molar ratio 1:1, apparently non-stoichiometrric, are nearly the same as those given for ammonium tetrachlorozincate in the literature. The 2:1 ratio is actually 'pseudo-stoichiometric' due to the hygroscopic nature of ZnCl 2 . The unit cell parameters of crystal grown from solution with molar ratio 2:1 match those of the structure (NH 4 ) 3 ZnCl 5 (A 3 ZC 5 ). The habit of the crystal grown in the former case, from solution with excess ZnCl 2 , was different from that of the crystal grown in the later case, from solution with excess (NH 4 )Cl. Between these two limits, a set of four samples were prepared from solutions with an excess of ZnCl 2 of 20, 30, 60 and 80 wt % in order to detect exact stoichiometric composition to grow A 2 ZC 4 . Analysis by X-ray diffraction shows that the first two crystals out of this set are mixed from A 2 ZC 4 and A 3 ZC 5 The third and fourth crystals still contain traces of A 3 ZC 5 . Analysis of the X-ray diffraction was then confirmed by DTA study. Irradiating A 2 ZC 4 with γ-dose of 250 kGy slightly increased the unit cell volume due to imperfections created by irradiation. Two computer programs were used to calculate the lattice constants and the results were compared.

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High pressure Brillouin scattering and energy dispersive X-ray diffraction study of (NH4)2ZnCl4

Cited by 12 publications

References 24 publications

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals

Doping‐induced‐effects on conduction mechanisms in incommensurate ammonium zinc chloride crystals

Effects induced by chemical non-stoichiometry and γ-irradiation on the habit and unit cell parameters of ammonium tetrachlorozincate

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High pressure Brillouin scattering and energy dispersive X-ray diffraction study of (NH4)2ZnCl4

Cited by 12 publications

References 24 publications

Temperature dependence of the indirect band gap and related optical parameters of (NH4)2ZnCl4:xSr2+ single crystals

Temperature dependence of the indirect band gap and related optical parameters of (NH4)2ZnCl4:xSr2+ single crystals

Doping‐induced‐effects on conduction mechanisms in incommensurate ammonium zinc chloride crystals

Effects induced by chemical non-stoichiometry and γ-irradiation on the habit and unit cell parameters of ammonium tetrachlorozincate

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Product

Resources

About

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals

Temperature dependence of the indirect band gap and related optical parameters of (NH₄)₂ZnCl₄:xSr²⁺ single crystals