IV. Order–disorder transitions: solid state kinetics, thermal analyses, X-ray diffraction and electrical conductivity studies in the Ag₂SO₄–K₂SO₄ system

Abstract

M. SUNITHA KUMARI and ETALO A. SECCO. Can. J. Chem. 63, 324 (1 985).Order-disorder transitions occurring in the Ag2S04-K2S04 system were investigated by reaction kinetics, thermal analyses, X-ray diffraction, and electrical conductivity techniques. Solid-liquid and solid-solid phase diagrams are reported.The conductivity data in the high temperature phase of the solid resemble superionic conductivity behavior. The higher conductivity of AglS04 with K+ presence relative to pure AgzSOJ and A g , , N a , S 0 4 compositions support a lattice expansion facilitating higher mobility of ions.The reaction kinetics, X-ray diffraction, and electroconductivity results suggest a relatively open periodic S O : sublattice in the high-temperature phase of the sulfate-based systems studied in this series.M. SUNITHA KUMARI et ETALO A. SECCO. Can. J. Chem. 63, 324 (1985). Faisant appel aux cinttiques de rCaction et aux techniques d'analyse thermique, de diffraction de rayons-X et de conductivitC Clectrique, on a Ctudit les transitions ordre-dCsordre qui se produisent dans le systeme Ag2S04-KZS04. On rapporte les diagrammes de phase solide-liquide et solide-solide.Les donnCs de conductivitC thermique de la phase a haute tempkrature ressemblent i un comportement de conductivitC superionique. Le fait que la conductivitk du Ag2S04, en prCsence de K', soit plus ClevCe que celle du Ag2S04 ii 1'Ctat pur ou de celles des compositions AgZ-,Na,S04 milite en faveur d'une expansion du reseau facilitant ainsi une mobilitt plus grande des ions.Les rtsultats observes avec les cinCtiques de rtaction, avec la diffraction de rayons-X et avec 1'ClectroconductivitC suggerent la presence d'un sous-rCseau +riodique d'ions ~~a -~u i est relativement ouvert dans la phase a haute tempirature des systemes a base de sulfates CtudiCs dans cette sCrie.[Traduit par le journal] Introduction Binary sulfates containing monovalent cations are members of a group of compounds which exhibit fast-ion or "superionic" conductivity-in the high temperature phase (I). such compounds are referred to as superionic conductors (SIC'S) or solid electrolytes and have attracted considerable attention because of (i) their promise in applications in high-energydensity batteries and (ii) their unusual transport behavior.The mechanism of fast-ion conduction is not completely understood although proposed models involve basically two structural types, viz. (i) layer structure as in p-alumina and (ii) channel structure as in a-AgI or in NASICON where an open network or skeleton framework of anions facilitates cation mobility (1). This paper is part of a continuing effort (2-4) to probe the nature of the phase transition, the structure of the high temperature phase and the effects of guest ions relating to the mechanism of fast-ion conductivity in binary sulfate systems.Our earlier study on Na' presence in Ag2S0, lattice revealed a decrease in conductivity in Ag2-,Na,SO, compositions attrib-

Electrical Conductivity and Phase Transition Studies in the ZrO₂-CdO System

“…The drop in conductivity beyond 180 ο C is due to the collapse of fluorite framework and on cooling the higher conductivity is regained. Such type of decrease in conductivity has been reported earlier [34,35,36]. Pure ZrO 2 shows a second rise in conductivity from 460 ο C onwards as its phase transition from monoclinic to tetragonal symmetry begins at 460 ο C and is completed around 1160 ο C [37].…”

Study of Ionic Conduction and Dielectric Behavior of Pure and K<sup>+</sup> Doped Ag<sub>2</sub>CdI<sub>4</sub>

“…CdI  framework and subsequently recovered on cooling which implies the restructuring of that sub-lattice [12].…”