Anomalous Behavior in the Electrical and Optical Properties of Ammonium Sulfate Single Crystals in the Temperature Range 250–350 K

Mohamad, Galal A.

doi:10.1143/jpsj.71.2550

Cited by 4 publications

(4 citation statements)

References 26 publications

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“…2 A marked discontinuity in the 14 N NMR spectrum was found in the vicinity of the ferroelectric phase transition, which is reported to be of the first-order. The splitting of the 14 N NMR resonance frequency in NH 4 + is larger in the paraelectric than in the ferroelectric phase, and we can say that the transition to the ferroelectric phase involves a change in the quadrupole parameter. Note that these temperature-dependent changes in the 14 N resonance frequencies are generally attributed to changes in the structural geometry near T C =223 K. Here, the electric field gradient (EFG) tensors at the N sites are varied, reflecting the changing atomic configurations around the 14 N nuclei.…”

Section: Resultsmentioning

confidence: 85%

“…Here, the N(1) and N(2) atoms corresponding to NH 4 (1) and NH 4 (2) ions, respectively, can be distinguished. Note that in the paraelectric phase, the low-frequency resonance is assigned to NH 4 (1) on the basis of 15 4 (1), while for NH 4 (2), e 2 qQ/h=2 kHz and η=1.0~0.8. 19 The four spectral pairs of signals as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…It is also known to be ferroelastic in both the paraelectric and ferroelectric phases. [4][5][6][7][8][9][10][11] At room temperature, the crystal possesses orthorhombic symmetry (space group Pnam-D 2h 16 ), with lattice constants a=7.782Å, b=10.636Å, and c=5.993 Å. 12 They undergo a phase transition without changing the number of formula units Z=4 in the unit cell at T C .…”

Section: Introductionmentioning

confidence: 99%

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Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR

Lim¹

2017

Journal of the Korean Magnetic Resonance Society

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The 14 N NMR spectra for (NH 4 ) 2 SO 4 crystals were obtained near the phase transition temperature T C =223 K, and were found to precisely reflect the symmetry change in the crystal at this first-order phase transition. Changes in the resonance frequencies near T C were attributed to the structural phase transition. In the ferroelectric and paraelectric phases, two inequivalent NH 4 groups were distinguished in the 14 N NMR spectra. The two types, NH 4 (1) and NH 4 (2), have slightly different local environments. Consequently, we conclude that the phase transition is caused by the change in the environment of the 14 N nuclei in the NH 4 groups, rather than by the SO 4 groups.

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Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR

Lim¹

2017

Journal of the Korean Magnetic Resonance Society

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“…The obtained optical transmittance spectrum of the pristine sample is identified to be in good agreement with the earlier reports. [57,58] Under shocked conditions, there are considerable changes observed and especially at the second shocked condition where a significant reduction of optical transmittance is observed because of the formation of the distorted-Pnam crystal symmetry. The distorted-Pnam crystal surface is significantly affected by the photondependent transport properties and hence the net optical transmittance has remarkably reduced at the second shocked condition.…”

Section: Ultraviolet Diffused Reflectance Spectroscopic Analysismentioning

confidence: 99%

Acoustic Shock‐Wave‐Induced Crystallographically Order–Disorder Switchable Phase Transition of Ammonium Sulfate Crystal: X‐Ray Diffraction and Raman Spectroscopic Approach

Aswathappa,

Palaniyasan,

Sathiyadhas

et al. 2024

Physica Status Solidi (b)

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In this framework, the authors have intended to examine the phase‐transition probability of ammonium sulfate (NH4)2SO4 under dynamic shock loaded conditions, whereby it is authenticated from the observations that the title crystal undergoes the process of reversible phase transition of crystallographic nature. The observed phase‐transition sequence is Pnam (crystalline) → Pnam (crystalline) → distorted Pnam (semicrystalline) → Pnam (crystalline) → Pnam (crystalline) under the exposure of 0, 1, 2, 3, and 4 shocks, respectively, such that the order of the transition is evaluated by diffraction and spectroscopic techniques. The obtained differential scanning calorimetry and thermogravimetric analysis results provide the crystalline‐state ammonium sulfate which has higher thermal stability than that of the disordered‐state ammonium sulfate. Analyzing the acquired results of the analytical experiments, the authentication can be arrived at such that the phase transition of reversible nature is enforced by the molecular distortions followed by the occurrence of rotational disorder involving ammonium and sulfate groups of ions influenced by the impulsion of shock waves thereby the title crystal can be a potential material for molecular switching applications.

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Optical properties of pure and metal ions doped ammonium sulfate single crystals

El‐Fadl

Anooz

2006

Cryst. Res. Technol.

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A study of the optical properties of pure-and some metal ions doped ammonium sulfate crystals (AS) were made. Optical constants of AS crystals were calculated at room temperature. The optical absorption coefficient (α) was analyzed and interpreted to be in the allowed direct transition. The introduction of Rb + or Cs + ions gives rise to an intense charge transfer band with a maximum at λ= 310 nm in the optical spectrum. In case of Cr 3+ -doping, the absorption shows a shoulder just before the onset band to band transition. The values of the allowed direct energy gap E g for undoped and doped crystals were calculated. It was found that E g values were decreased with metal ions doping. The refractive index, the extinction coefficient and both the real and imaginary parts of the dielectric permittivity were calculated as a function of photon energy. The validity of Cauchy-Sellimeier equation was checked in the wavelength range 4.9 -5.6 eV and its parameters were calculated. Applying the Single-Effective-Oscillator model, the moments of ε(E) could be estimated.

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Anomalous Behavior in the Electrical and Optical Properties of Ammonium Sulfate Single Crystals in the Temperature Range 250–350 K

Cited by 4 publications

References 26 publications

Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR

Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR

Acoustic Shock‐Wave‐Induced Crystallographically Order–Disorder Switchable Phase Transition of Ammonium Sulfate Crystal: X‐Ray Diffraction and Raman Spectroscopic Approach

Optical properties of pure and metal ions doped ammonium sulfate single crystals

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Anomalous Behavior in the Electrical and Optical Properties of Ammonium Sulfate Single Crystals in the Temperature Range 250–350 K

Cited by 4 publications

References 26 publications

Paraelectric-Ferroelectric Phase Transition of (NH4)2SO4 Single Crystals by 14N NMR

Paraelectric-Ferroelectric Phase Transition of (NH4)2SO4 Single Crystals by 14N NMR

Acoustic Shock‐Wave‐Induced Crystallographically Order–Disorder Switchable Phase Transition of Ammonium Sulfate Crystal: X‐Ray Diffraction and Raman Spectroscopic Approach

Optical properties of pure and metal ions doped ammonium sulfate single crystals

Contact Info

Product

Resources

About

Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR

Paraelectric-Ferroelectric Phase Transition of (NH₄)₂SO₄ Single Crystals by ¹⁴N NMR