Electric and Optical Properties Near the Successive Phase Transition Points of Rubidium Nitrate Crystal

Study of dielectric properties of RbNO3 single crystals

“…Finally, at lower frequencies near microwave and lower dipolar, the contribution becomes significant. This result is in accordance with Kawashima et al results [5] measured at 1 kHz and Fujimoto et al results [10] at 1 MHz. Thus the large value of dielectric constant at low frequency suggests that there is a contribution from all four known sources of polarization, namely electronic, ionic, dipolar and space charge polarization of which the latter is known to contribute strongly at low frequencies [14].…”

“…There have been some studies reported on the variation of dielectric constant (k) and dielectric loss (tan 5) with temperature [5,[8][9][10], but none of the investigations studied the variation of dielectric constant, dielectric loss and a.c. conductivity with both frequency and temperature and correlated the three. Our study of these ,transformations by measuring the d.c. conductivity with temperature [11] shows that the transition IV to III at about 160°C is predominant, associated with the maximum variation of conductivity.…”

The microwave cavity perturbation technique for contact-free and in situ electrical conductivity measurements in catalysis and materials science

“…[37][38][39] The appropriate phase transitions are related to orientational disorder of nitrate ions, and thus are accompanied by escalating changes in the complex permittivity. This was studied by MCPT at 9.2 GHz with the calibrated reactor setup described before.…”

“…Starting at room temperature with a trigonal phase (IV) isomorphous with CsNO 3 , RbNO 3 undergoes at 164 1C a phase transformation to a cubic CsCl structure (III), at 219 1C to a rhomboedral (II) and at 285 1C to a cubic NaCl phase (I). [37][38][39] The appropriate phase transitions are related to orientational disorder of nitrate ions, and thus are accompanied by escalating changes in the complex permittivity. This was studied by MCPT at 9.2 GHz with the calibrated reactor setup described before.…”

“…According to the literature these steps and peaks, respectively, can be assigned to the IV-III, III-II, II-I phase transformations, and the melting point of RbNO 3 , respectively. [37][38][39] The increase of e 2 at the IV-III transition was assigned to a rise in the ionic conductivity (caused by cation Frenkel defects), which is after eqn (7) proportional to e 2 if other dielectric losses can be neglected, caused by increased rubidium-nitrate ion distances in the crystal. Interestingly, just before the III-II transformation indicated by the appropriate endothermic DSC peak at 223 1C both e 1 and e 2 exhibit a sharp rise and a successive less steeper decline.…”