Dataset for correlation in γ -RbAg4I5 between ionic conductivity relaxation and specific heat.

Using the ac-calorimetry technique and the electric modulus formalism for analysis of ionic conductivity relaxation in crystalline γ -RbAg4I5, close to the γ to β phase transition at 120 K, the temperature derivative of microscopic interaction energy for a single-mobile ion is proportional to the specific heat. The two different experimental techniques show that cooperative behavior drives the phase transition at 120 K (obey the same mechanism).

Temperature-dependent data of single ion microscopic energy give the vision to explain the dynamics near the -to- first-order transition in crystalline superionic system RbAg4I5 at 120 K.

Data

Fig. 1 shows a discontinuous change of the dc-conductivity with an associated peak in the excess specific heat of RbAg4I5 where the first-order phase transition occurs at 120 K or phase boundary is between the - RbAg4I5 and - RbAg4I5 [1], [2], [3]. The value of enthalpy corresponding to the phase transition is provided by the migration energy, which allows us to correlated both thermodynamics and transport concepts.

Fig. 1

The specific heat at a constant pressure of RbAg4I5 as a function of temperature. At 120 K, the first-order phase transition occurred.

Experimental design, materials and methods

Using the solution technique with high purity reagents [4], the RbAg4I5 crystals at 318 K and dried at 390 K for about 6 hours were grown. For the crystallographic analysis, the crystal samples are a representative specimen.

Using the ac-calorimetry technique [5], [6], the specific heat data of RbAg4I5 single crystals were continuously obtained. Using dry abrasives crystal slices were thinned to 0.1 mm. By light chopped at 1.5 Hz, the sample was heated. Using a 25 m type-K thermocouple, the temperature oscillations induced in the sample, inversely proportional to the specific heat, were monitored. The sample was swept slowly through the region of the phase transitions to obtain the specific heat at constant pressure as a function of the temperature .

Using the two-electrode configuration Ag|RbAg4I5|Ag with silver paste as electrodes, an electrical measurement was made. By admittance spectroscopy in 20 Hz to 3 MHz frequency range, using a precision LCR meter HP 4284A and at different fixed temperatures between 105 K and 121 K, under a dry nitrogen atmosphere, the electrical characterization was done. The amplitude of the applied ac signal was 10 mV.

In the crossover region, the dependence of the real part of the ac conductivity , is described for ionic conducting materials by a power law [7]:where is a characteristic relaxation, is the dc conductivity, and is the power-law exponent related to the degree of correlation among moving ions [8]. The frequency dependence of the real part of the ac conductivity for isotherms in the 116 k to 124 K temperature range is shown in Fig. 2.

Fig. 2

Real part of the electrical conductivity as a function of frequency for (116–124) K temperature range.

The parameters and were obtained by fitting the data at various isotherms according toand the Arrhenius plot [log() as a function of ] is shown in Fig. 3.

Fig. 3

Real part of the electrical conductivity as a function of the inverse of temperature.

Activation energy, , is non-Arrhenius in the 118.4 k to 119.8 K temperature range for dc-conductivity data.

Frequency dependence of the imaginary part of the dielectric modulus is shown in Fig. 4 at several temperatures range (117.5 K and 119.8 K):

Fig. 4

Dependence of frequency of the real part of the electrical modulus for 117.5 and 119.8 K temperature range.

-correlation function, the activation, microscopic and migration energies as a function of temperature is shown in Fig. 5 for 117.5 K and 119.8 K temperature range.

Fig. 5

-correlation function, the activation, microscopic and migration energies as a function of temperature.

Results of d(Eact)/dT and is shown in Fig. 6 the where these quantities exhibit similar behavior with temperature.

Fig. 6

Results of d(Eact)/dT (solid line) and (filled spheres) as a function of temperature near and below transition region.

Specifications Table

Subject area	Physics
More specific subject area	Experimental condensed matter
Type of data	Graphs, figures
How data was acquired	Specific heat measurements, conductivity-frequency profile, raw data were analyzed by Origen software
Data format	Raw, analyzed, fitted
Experimental factors	Data of conductance are computed using KWW model, Jonscher equation, and K. Ngai model
Experimental features	Specific heat data were taken by an automatized high-resolution ac calorimeter and conductance data by a commercial impedance bridge.
Data source location	City of Cali, Colombia
Data accessibility	Data are provided in this current article

Value of the data• Temperature-dependent data of single ion microscopic energy give the vision to explain the dynamics near the γ-to-β first-order transition in crystalline superionic system RbAg4I5 at 120 K. • It is well known that for the first-order phase transition takes place, the internal energy necessary to obtain it, corresponds to the thermally provided activation energy. The data shows that only the migration energy contributes to the phase transition in this compound. • The data for measurements of specific heat and conductance can be used to demonstrate that both experimental techniques share the same origin.