Thermal anomaly in sodium potassium sulphate crystals

Kassem, M. E.; Kandil, Sherif; El‐Wahidy, E. F.; El-Gamal, M. A.

doi:10.1051/rphysap:01984001906044500

Cited by 15 publications

(6 citation statements)

References 3 publications

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“…Single crystals of (NaxK1-x)2SO4 were grown by the dynamical and slow evaporation method [4] at constant temperature of 315 K from aqueous solutions of different stoichiometric ratios of pure Na2SO4 and KzSO4. The stoichiometric ratio x was chosen to be x = 0.2, 0.3, 0.4, 0.8 and 0.9.…”

Section: Methodsmentioning

confidence: 99%

“…In an early work, Kassem et al [4] have studied the thermal properties of NaKSO4 single crystal (x = 0.5). It has been suggested that under normal conditions, the pure NaKSO4 crystal may exhibit a structural phase transition at about 453 K. Those authors argue that the transition is probably from orthorhombic symmetry with point group mmm to monoclinic symmetry with point group 2/m.…”

Section: John Wiley and Sons Limited Chichester Akad~miai Kiad6 Budamentioning

confidence: 99%

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Stoichiometric ratio and doping effects on the thermal properties of sodium potassium sulphate crystals

Abboudy

Hamed

Kassem

et al. 1993

Journal of Thermal Analysis

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The influence of stoichiometric ratio on the phase transition of sodium potassium sulphate (NaxKl-x)2SO4 crystals is investigated in the temperature range 300-500 K. The stoichiometric ratio x is chosen to be x = 0.2, 0.3, 0.4, 0.8 and 0.9. The study has been carded out by using differential scanning calorimetry, DSC technique. The value of the specific heat, Cp, at the transition temperature, To, increases as x is increased up to x = 0.4 and then decreases for higher values of x. The change in the specific heat, ACp, is following a relation of the form AC~ o~(T-Tc/Tc) "~ with o~ = 0.12 which is in a fair agreement with the 3d Ising model. Insertion of Cu ions into the lattice of (NaxKl-x)2SO4 crystals leads to a multiple peak in the temperature dependence of Cr,. The results are discussed from thermodynamical point of view.

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Section: Methodsmentioning

confidence: 99%

Section: John Wiley and Sons Limited Chichester Akad~miai Kiad6 Budamentioning

confidence: 99%

Stoichiometric ratio and doping effects on the thermal properties of sodium potassium sulphate crystals

Abboudy

Hamed

Kassem

et al. 1993

Journal of Thermal Analysis

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“…Thermomechanical analysis (TMA) was carried out using a Heraeus TMA 500 dilatometer, as described previously (Kassem, Kandil, El-Wahidy and El-Gamal, 1984).…”

Section: Methodsmentioning

confidence: 99%

Thermal expansion of LATGS crystals

et al. 1990

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The thermal expansion of triglycine sulphate crystals doped with L-a alanine (LATGS) has been studied around the phase transition temperature (30-60°C) using thermomechanical analysis, TMA. With increasing content of admixture, the transition temperature (T,) was shifted towards higher values, while the expansion of the crystals (ALIL,) varied both in the para and ferroelectric phases.The transition width in doped crystals was found to be. broad, and this broadening increased with increasing content of L-a alanine.

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“…During our previous studies of the thermal properties of NaKSO4 crystals, anomalous behaviour of the specific heat (Cp) was observed at 453 K [2]. Upon irradiation of the crystal the position of the peak representing the change in Cp with temperature, was found to vary with irradiation dose.…”

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confidence: 96%

“…Non-irradiated NaKSO4 crystals, when heated, showed an anomaly at 453K [2], as the thermal expansion coefficient measured along the Z-axis had a negative value.…”

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confidence: 99%

Inhomogeneous strain induced by fast neutron irradiation in NaKSO4 crystals

et al. 1987

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A characteristic first-order phase transition of a solidsolid transformation in NaKSO4 crystals was observed using thermal analysis, infrared and X-ray diffraction techniques [1]. Previous studies of thermal properties of NaKSO4 crystals showed an anomaly in the temperature dependence of specific heat (Cp), linear thermal expansion coefficient, ~j, and heat transition, AQ, at 453 K [2]. These observations were confirmed by the results of the electrical conductivity in the same temperature range [3].The electrical conductivity measurements in the temperature range 300 to 500 K of NaKSO 4 crystals irradiated by fast neutrons of 14.5MeV energy, showed a pronounced change in the phase-transition temperature [4].In this letter the effect of neutron irradiation on the thermal properties of NaKSO4 crystals, in the same temperature range, was studied and the effect of the induced inhomogeneous strain was noted.Stoichiometric ratios of NazSO 4 and KzSO 4 were added to produce NaKSO4 crystals which were purified five times. Large single crystals were grown by means of slow dynamical isothermal evaporation methods [5].Chemical analysis, X-ray diffraction and optical inspection were used for purity control and to ensure the quality of the crystal.A Heraeus TMA 500 dilatometer was used for the thermomechanical analysis measurements. The sample temperature was monitored by means of a Ni-Cr-Ni thermocouple fitted in a sample holder of standard design which was made of quartz. The linear expansion coefficient was calculated on the assumption that the quartz expansion coefficient has an insignificant effect on the measured values, the heating rate used was 2 K min-~. The samples were shaped from a large single crystal of NaKSO4 in the form of rectangular rods whose dimensions were 2 x 2 x 20mm 3. The longer part of the sample was oriented along the crystallographic direction (0 0 1).The specific heat under constant pressure, Cp, was determined using a differential scanning calorimeter (DSC) technique, where a Heraeus DSC cell was connected to the Heraeus DTA 500 thermal analyser. Measurements were performed by applying the base line methods [6]. Lidded pans, made of aluminium, were used to eliminate the sloping of the base line. A Pt-100 thermocouple was used as the temperature sensor while a heating rate of 2 K min-1 was applied.The samples were irradiated by different neutron doses at room temperature (298 K) using a compact 0261 8028/87 $03.00 + .12

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Thermal anomaly in sodium potassium sulphate crystals

Abstract: Résumé. 2014 Les propriétés thermales du NaKSO4 cristal, que l'on a fait croître à 315 K par la méthode d'évapora-tion lente, ont

Cited by 15 publications

References 3 publications

Stoichiometric ratio and doping effects on the thermal properties of sodium potassium sulphate crystals

Stoichiometric ratio and doping effects on the thermal properties of sodium potassium sulphate crystals

Thermal expansion of LATGS crystals

Inhomogeneous strain induced by fast neutron irradiation in NaKSO4 crystals

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