AC Conductivity, XRD and transport properties of melt quenched PbI2–Ag2O–Cr2O3 system

Abstract

Composite materials used for electrode and electrolyte materials have been intensely studied in view of their advantages such as higher conductivity and better operational performance compared to their single-phase counterparts. The present work aims at studying the electrical and structural characteristics of a new composite electrolyte namely, (PbI 2 ) x −(Ag 2 O-Cr 2 O 3 ) 100−x where x=5, 10, 15, 20, and 25 mol%, respectively, prepared by the melt quenching technique. The room temperature X-ray diffraction spectra revealed certain crystalline phases in the samples. AC conductivity analysis for all the prepared samples was carried out over the frequency range 1 MHz-20 Hz and in the temperature window 297-468 K. The room temperature conductivity values were calculated to be in the order of 10 −5 -10 −3 Scm −1 . An Arrhenius dependence of temperature with conductivity was observed, and the activation energies calculated were found to be in the range 0.27-0.31 eV. Furthermore, the total ionic transport number (t i ) values obtained for all these indicated the ionic nature of this system.There has been a considerable interest in studying fast ion conducting solid electrolytes that exhibit high ionic conductivity at temperatures well below their melting points. The demonstration of such electrical properties by these materials make them potential candidates for various electrochemical applications viz., solid-state batteries, sensors, fuel cells, etc.[1]. It is noteworthy to mention here that among these electrolytes, although the class of AgIbased electrolytes offering promising characteristics have been fairly reported in literature [2], the scope for further exploration in this field is still wide open. The important feature that attract researchers toward such an exploration in materials with potential mobile ions as Ag + ion lies in certain inherent features of these electrolytes as their isotopic properties, ease in preparation, high room temperature conductivities, etc. More recently, the trend of replacing Ag + ions with other feasible cations in dopants like CuI, CdI 2 , etc. has been followed to realize new materials exhibiting comparable electrical conductivities and exploiting the favorable character of silver ion to electrical conduction [3,4]. Moreover, this new route adopted in developing such materials has paved the way for the "mixed cation effect" [5] wherein a second cation is involved in the process of conduction actively or by influencing conductivity via structural alterations. In view of this, the present study aims to study the effect due to varying concentrations of a new dopant salt, PbI 2 , on conductivity in the case of the system PbI 2 -Ag 2 O-Cr 2 O 3 . It is crucial to note that the network former/modifier ratio also plays a dynamic role in influencing the overall electrical conductivity. However, a study on one such similar ternary system has observed efficient values of conductivity for network former/modifier ratio of one [6]. Hence the above ratio has been maintained at 1 througho...

Preparation, characterization, electrical and dielectric properties of (1−x) (PbI2–Ag2CrO4)–xTiO2 composite solid electrolytes

“…The thermo grams of pure PbI 2 -Ag 2 CrO 4 resolved into two distinct endothermic peaks at the temperature 150 ℃ and 558 ℃ correspond to the phase transition (β →α) as well as the melting point of AgI. Existence of these peaks in the spectra confirms the presence of AgI component, which is formed due to the ion exchange of Ag + and Pb 2+ ions [37,38]. In case of the x=0.2, 0.3 and 0.4 composite samples, hump of the phase transition was decreased upon increasing the concentration of TiO 2 .…”

The Effect of Mixed Iodide Salts on the Conductivity Behavior in Ag2O-V2O5-B2O3 Superionic Glass System

“…The value of the bulk resistance of the sample was estimated from the low frequency intercept of the complex impedance plot using this resistance value, the dc conductivity is estimated [9]. salts [3][4][5][6]. In the presently investigated system, the Ag + ions bonded to the non-bridging oxygen have less freedom to move and are expected to be less mobile compared to the Ag + ions in an iodine environment.…”

“…In the present case, Cu + , a transition metal cation is expected to be a soft acid, does not undergo exchange reaction under HSAB whereas, AgI, which is formed by the ion exchange reaction between PbI 2 and Ag 2 O by the Hard and Soft Acids and Bases (HSAB) principle, participates in the conduction process. Since, PbI 2 is a heavy metal salt which is reported to behave as modifier as well as former, the increase in concentration may produce structural alteration and formation of inhomogeneous ionic clusters [3,4,11]. It is also known that borate glass is assumed to consist of a random threedimensional network of nearly flat BO 3 triangles with a comparatively high fraction of six member boroxol rings [12].…”

“…Electrical properties of silver oxy-salt based solid super ionic electrolytes with different glass modifyers and formers have been widely reported in the past [1][2][3]. Some reports on the replacement of Ag + ion with other feasible cation like CdI 2 , PbI 2 , CuI in the glass electrolytes are also available in literature [3][4][5]. Many interesting results have been obtained regarding the nature of electrical conductivity of these glasses.…”

Structural characterization and complex impedance studies on fast ion conducting mixed system (SbI3) x –(Ag2CrO4)1−x

“…In order to arrive at new series of fast ionic systems in a cost-effective manner, researchers in the recent past replaced AgI with other metal halides such as CdI 2 , CuI, ZnI 2 , PbI 2 and alkali halides like NaI or KI Suthanthiraraj 1992, 1993;Padmasree et al 2005;Suthanthiraraj and Vinod Mathew 2005) resulting in electrical conductivities comparable to that of their AgI-based counterparts. On the other hand, the presence of certain cations such as Cs + , Cu + , Zn 2+ , Pb 2+ or Sb 3+ ion led to possible coordination with the oxygen ion within the oxyanion framework thereby facilitating easy conduction pathways for Ag + ions to move towards an iodinerich environment (El Damrawi et al 2000;Renard et al 2002) and the role of silver oxysalt Ag 2 CrO 4 in forming glassy networks has already been well established in the literature (Viswanathan and Suthanthiraraj 1992;Durga Rani and Hariharan 1996).…”