| Autor: |
Щепанський, П. А., Стадник, В. Й., Пришко, І. А., Брезвін, Р. С., Онуфрів, О. Р., Когут, З. |
| Zdroj: |
Journal of Physical Studies; 2024, Vol. 28 Issue 1, p1-7, 7p |
| Abstrakt: |
Temperature changes of linear expansion and refractive indices of rubidium sulfate (RS) Rb2SO4 crystals were investigated in the work. It was established that the linear dimensions increase as the temperature increases. For the Z-direction (the direction of occurrence of ferroelastic deformation) these changes are significant. The temperature dependence of the spontaneous deformation δχz was calculated, and it was found that the value of δχz decreases parabolically as the temperature increases. DTA was carried out and derivatogramm and thermogravimetrogramm of RS crystal were obtained. At the temperature of 923 K, a clear anomaly was found, which corresponds to the position of the phase transition (PT) point, which is endothermic in nature. In the temperature range of 625-738 K, a loss of the mass of the sample was detected, which was caused by the thermal decomposition of OH+3 ions and the emission of H2 and O2 molecules. It was established that the temperature changes of the refractive indices ni of Rb2SO4 crystal decrease non-linearly as the temperature increases, and |dnz/dT| > |dnx/dT| ≥ |dny/dT|. During the PT, no jump-like changes in ni(T) were detected, which is characteristic of PT of the 2nd kind. The values of spontaneous changes in refractive indices δnsi (T) were obtained. These are similar in behavior to the experimentally obtained dependence χsi (T) and can be described by a parabolic dependence. Using the obtained experimental values, the critical index of changes δnsi (T) was estimated (β = 0.21), which corresponds to the values derived from Landau's thermodynamic theory for PT. It is assumed that the main cause of the detected changes in the vicinity of the PT is defects of the "random temperature" type. The temperature change of the electronic polarizability α(T) of the Rb2SO4 crystal was estimated. It characterizes the degree of displacement of the structural elements from the equilibrium position under the action of the external electric field of the incident light wave. In the PT region, the dependence of α(T) has a complex anomalous character: it slightly decreases as the temperature increases, and after the PT, the value of α(T) practically does not change with temperature. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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