Zur Ionenleitung und Fehlordnung von Silberbromid mit Zusätzen zweiwertiger Kationen. I Leitfähigkeitsmessungen und Zustandsdiagramme

Abstract

InhaltsiibersichtDie elektrische Leitfahigkeit von festem Silberbromid mit Zusiitpen von CdBr,. sowie PbBr,, CaBrz und ZnBrz wird in dern durch eine &sondere Untersuchung ermittelten homogenen Mischkristallgebiet bei verschiedenen Temperaturen gemessen. Dabei treten individuelle Einfliisse der Zusatzionen gegeniiber dem Effekt ihrer doppelten Ladung weit zuriick.

Creation and Recombination of Frenkel Defects in AgBr

“…On the basis of temperature dependent conductivity and tracer diffu sion data as well as model calculations, various migra tion enthalpies have been derived, the lowest applying to the collinear interstitialcy mechanism [7, 8], In 1961 Everett et al [9] published microwave con ductivity data of AgBr, taken at 23 GHz. The conduc tivity was found to be significantly larger at 23 GHz than at 1 kHz [2][3][4], and the effect was attributed to a Debye-Falkenhagen type of relaxation [10,11] of the mobile silver ions. In an effort to substantiate the findings of Everett et al we have performed conduc tivity measurements in a broad frequency range.…”

“…It is a fast ionic conductor at temperatures well below its melting point, with a conductivity of 0.1 f t-1 cm-1 at about 625 K [2][3][4], The cation mobility in AgBr is caused by the thermally activated formation of Frenkel defects in the rocksalt structure, the Frenkel-pair formation enthalpy being about 1.15 eV [5,6]. On the basis of temperature dependent conductivity and tracer diffu sion data as well as model calculations, various migra tion enthalpies have been derived, the lowest applying to the collinear interstitialcy mechanism [7,8],…”

Self-Diffusion of the Silver Ion in Pure Silver Chloride

“…stitial jumps occur simultaneously in the AgC1 lattice, with the number of collinear interstitialcies predominating because of their lower activation energy. In addition, as the temperature increases, more of the noncollinear interstitial,jumps will be activated and will in turn produce an increase in the overall value of the correction 32 factor f.. 1 An experimental verification of these theoretically expected 17 results has been done by Friauf, who made conductivity and radioactive tracer diffusion measurements on pure AgBr crystals. These experiments yielded values of lj = 0.078 ev and U = 0.225 ev respectively for the collinear and noncollinear jumps, which is in reasonable agreement with Hove's results for AgC1.…”

Limites des solutions solides dans le système binaire CdBr2-AgBr

“…La teneur en dopant n'a pas excédé 1 % mol. Cependant, les travaux de Vomhof et Nolting [IO] ainsi que ceux de Teltow [2] ont démontré l'existence d'une solution solide plus étendue à base de AgBr à haute température, contenant pas moins de 8 % mol. CdBr2 au-dessus de 500 K [IO] et 30 % mol CdBr2 au dessus de 673 K [2].…”